Bromelain does not provide significant analgesic and anti-inflammatory benefits over placebo in cats undergoing ovariohysterectomy

Matheus R. Ribeiro Department of Veterinary Surgery and Anestesiology, Faculty of Veterinary Medicine, Universidade do Oeste Paulista, Presidente Prudente, Brazil

Search for other papers by Matheus R. Ribeiro in
Current site
Google Scholar
PubMed
Close
 DVM, MSc
,
Maria Eduarda B. A. M. Conceição Neuropet, Veterinary Clinic, Belém, Brazil

Search for other papers by Maria Eduarda B. A. M. Conceição in
Current site
Google Scholar
PubMed
Close
 DVM
,
Danielle K. O. Bezerra Neuropet, Veterinary Clinic, Belém, Brazil

Search for other papers by Danielle K. O. Bezerra in
Current site
Google Scholar
PubMed
Close
 DVM
,
João Paulo P. Teles Neuropet, Veterinary Clinic, Belém, Brazil

Search for other papers by João Paulo P. Teles in
Current site
Google Scholar
PubMed
Close
 DVM
,
Rogério Giuffrida Department of Veterinary Surgery and Anestesiology, Faculty of Veterinary Medicine, Universidade do Oeste Paulista, Presidente Prudente, Brazil

Search for other papers by Rogério Giuffrida in
Current site
Google Scholar
PubMed
Close
 DVM, MSc, PhD
, and
Renata N. Cassu Department of Veterinary Surgery and Anestesiology, Faculty of Veterinary Medicine, Universidade do Oeste Paulista, Presidente Prudente, Brazil

Search for other papers by Renata N. Cassu in
Current site
Google Scholar
PubMed
Close
 DVM, MSc, PhD

Click on author name to view affiliation information

Abstract

OBJECTIVE

To evaluate the efficacy and safety of bromelain to control pain and inflammation in cats undergoing ovariohysterectomy.

ANIMALS

30 client-owned cats undergoing ovariohysterectomy.

PROCEDURES

In a randomized, blinded clinical study, cats were assigned to receive either oral bromelain suspension (40 mg/kg [18 mg/lb]; BG, n = 15) or placebo solution (0.1 mL/kg [0.045 mL/lb]; PG, 15), which were administered 90 minutes before and 12 hours after surgery. The anesthetic protocol included acepromazine, meperidine, propofol, and isoflurane. Pain and sedation were assessed at various time points up to 24 hours post-extubation using the UNESP-Botucatu multidimensional composite pain scale, the Glasgow feline composite measure pain scale, and a descriptive numerical scale. Surgical wound inflammation was measured at the same time points, using a numeric rating scale. Morphine was administered as rescue analgesia. Laboratory data (urea, creatinine, gamma-glutamyl transferase, alkaline phosphatase, the prothrombin time, and the fecal occult blood) were analyzed preoperatively and 24 hours after surgery.

RESULTS

Pain/inflammation scores, and analgesic requirements did not differ between groups. Shorter recovery time and lower sedation scores were recorded during the first hour post-extubation in the BG than the PG. Postoperatively, serum creatinine and gamma-glutamyl transferase were lower in the BG compared to PG. Compared to baseline values, all biochemistry variables decreased at 24 hours in the BG. The prothrombin time and fecal occult blood did not differ between groups or over time.

CLINICAL RELEVANCE

Bromelain did not provide significant analgesic and anti-inflammatory benefits over placebo in cats undergoing ovariohysterectomy.

Abstract

OBJECTIVE

To evaluate the efficacy and safety of bromelain to control pain and inflammation in cats undergoing ovariohysterectomy.

ANIMALS

30 client-owned cats undergoing ovariohysterectomy.

PROCEDURES

In a randomized, blinded clinical study, cats were assigned to receive either oral bromelain suspension (40 mg/kg [18 mg/lb]; BG, n = 15) or placebo solution (0.1 mL/kg [0.045 mL/lb]; PG, 15), which were administered 90 minutes before and 12 hours after surgery. The anesthetic protocol included acepromazine, meperidine, propofol, and isoflurane. Pain and sedation were assessed at various time points up to 24 hours post-extubation using the UNESP-Botucatu multidimensional composite pain scale, the Glasgow feline composite measure pain scale, and a descriptive numerical scale. Surgical wound inflammation was measured at the same time points, using a numeric rating scale. Morphine was administered as rescue analgesia. Laboratory data (urea, creatinine, gamma-glutamyl transferase, alkaline phosphatase, the prothrombin time, and the fecal occult blood) were analyzed preoperatively and 24 hours after surgery.

RESULTS

Pain/inflammation scores, and analgesic requirements did not differ between groups. Shorter recovery time and lower sedation scores were recorded during the first hour post-extubation in the BG than the PG. Postoperatively, serum creatinine and gamma-glutamyl transferase were lower in the BG compared to PG. Compared to baseline values, all biochemistry variables decreased at 24 hours in the BG. The prothrombin time and fecal occult blood did not differ between groups or over time.

CLINICAL RELEVANCE

Bromelain did not provide significant analgesic and anti-inflammatory benefits over placebo in cats undergoing ovariohysterectomy.

Introduction

In veterinary medical practice, perioperative inflammation and pain are mainly controlled by the provision of non-steroidal anti-inflammatory drugs (NSAIDs) combined with opioids.13 Despite the clinical efficacy of NSAIDs, the safety of these medications has been questioned, especially in cats which are more susceptible to undesirable renal effects, particularly in the presence of intraoperative hypotension.4,5

As an alternative to NSAIDs, herbal medications with anti-inflammatory and analgesic proprieties may represent a viable pharmacological strategy to provide therapeutic benefits, with minimal adverse effects in surgical patients.6,7 Among these medications, bromelain is a standardized complex of proteolytic enzymes extracted from pineapple plants (Ananas comosus), which was became commercially available in the mid-1950s, and since then numerous studies on its biological proprieties and clinical applications have been published.812

The mechanism of action of bromelain has not been completely elucidated. Data from animal studies suggest that the antinociceptive and anti-inflammatory effects of bromelain are mediated mainly by inhibition of the ciclooxigenase-2 (COX-2) enzyme, leading to a decrease in pro-inflammatory cytokines.11 Bromelain was also found to have fibrinolytic properties, which increase tissue permeability and contribute to the reabsorption of edema.12,13 Furthermore, a recent study reported that oral administration of bromelain in mice increased the release and absorption of active endogenous opiates in jejunum mucosa, which may also justify the antinociceptive effects attributed to this proteolytic enzyme.14 In addition to these effects, in vivo and in vitro studies have demonstrated reduced platelet aggregation and prolonged prothrombin time following bromelain administration,12,13,1517 which could limit its use in surgical patients, especially those with coagulation abnormalities. However, these effects were not confirmed in clinical studies that reported no significant differences in blood clotting mechanisms in human patients.18,19

Although the analgesic and anti-inflammatory proprieties of bromelain have been recognized for many decades, there is no reliable information regarding its application for perioperative pain management in veterinary patients. In humans, oral administration of bromelain reduced pain, edema, and inflammation after third molar extraction, rhinoplasty, episiotomy, and ophthalmic surgery.2023

The aim of this study was to determine whether perioperative oral administration of bromelain would decrease postoperative pain and inflammation and the need for supplementary analgesia in cats undergoing elective ovariohysterectomy. The hypothesis was that bromelain would improve analgesia and reduce inflammation, with minimal adverse effects.

Materials and Methods

Study design and ethics

This study was approved by the Institutional Animal Care Committee (protocol 7102/2020 CEUA) and was conducted according to The Consolidated Standards of Reporting Trials (CONSORT guidelines). Informed written consent for the investigation was obtained from all owners. A prospective, randomized, blinded, placebo-controlled clinical study was designed to investigate the effects of bromelain on postoperative pain, inflammation, and analgesic requirements.

Animals

From January to June 2022, 30 client-owned cats of different breeds, scheduled for elective ovariohysterectomy were enrolled. For inclusion, cats were required to be aged ≥ 6 months, weigh ≥ 2 kg, and to have normal laboratorial tests [complete blood count, blood coagulation (prothrombin time test), serum clinical biochemistry analysis, and fecal occult blood test]. Additionally, an abdominal ultrasonography exam was performed in all cats preoperatively. The exclusion criteria were: pregnancy, lactation, aggressive behavior, systemic diseases, and treatment with any anti-inflammatory or anticoagulant medications for at least 15 days before the study initiation. The cats were admitted to the hospital at least 36 hours prior to surgery for acclimatization. Before each experiment, the cats were fasted overnight with free access to water.

Treatment allocation and anesthetic procedure

Cats were randomly allocated to receive either bromelain (40 mg/kg/0.1 mL/kg [18 mg/lb/0.045 mL/lb]; BG, n = 15) or placebo (0.1 mL/kg [0.045 mL/lb]; PG, n = 15), which were orally administered using a syringe to ensure the complete ingestion of both treatments. Bromelain (400 mg/mL) and placebo (saline solution) were compounded as a bacon flavored oral suspension by a compounding pharmacy (Botica Magistral SA). The bromelain formulation was prepared from waste pineapple stem material, which has been referred to as stem bromelain. Veterinarians should adhere to compounding regulations and be aware that pharmacokinetic properties may differ among compounded products.

A random number generator (Research Randomizer; www.randomizer.org/) was used to assign 15 cats to each of the 2 groups with block randomization. Both treatments were administered 90 minutes before and 12 hours after surgery by 1 veterinary student who was not involved in the postoperative monitoring.

All anesthetic procedures were performed by the same anesthetist who was blinded to the group allocation. The cats were premedicated with 0.05 mg/kg [0.022 mg/lb] acepromazine (Acepran 0.2%; Vetnil) combined with 6 mg/kg [2.72 mg/lb] meperidine (Dolosal; Cristália) administered as a single IM injection. The cephalic vein was aseptically catheterized, and anesthetic induction was performed with IV propofol to effect (4 to 7.5 mg/kg [1.8 to 3.4 mg/lb]; Propovan; Cristália). Anesthesia was maintained by isoflurane (Isoforine; Cristália) vaporized in 100% oxygen (300 mL/kg/min [136 mL/lb/min]), using a nonrebreathing system (SAT 500; Takaoka). The cats breathed spontaneously throughout the procedure. Body temperature was maintained between 37 °C and 38 °C using a thermal warming blanket (Warm Air WA-7001; Hefei Longshore Tech).

Lactated Ringer solution was administered IV at 2 mL/kg/h [0.91/mL/lb/h] until extubation. Intraoperatively, the cats were continuously monitored using a multi-parametric monitor (Life Window 9X; Digicare Animal Health) including an electrocardiogram, oxicapnography, esophageal temperature, and non-invasive arterial blood pressure.

A single experienced surgeon performed the surgical procedure, using a standard technique, through median laparotomy access in supine cats. Duration of anesthesia (time elapsed from the administration of propofol to discontinuation of isoflurane), duration of surgery (time elapsed from the first incision until placement of the last suture), time to extubation (time elapsed from termination of isoflurane until orotracheal tube removal), and time to recovery (time elapsed from discontinuation of isoflurane until voluntary movement into a sternal position) were recorded for each cat. Extubation was performed when the cat recovered palpebral reflexes.

Pain and sedation scores

During the first 24 hours after extubation, pain, sedation, and inflammation scores were assessed by a single observer who was blinded to the treatment allocation and trained prior to this study in clinical patients to measure pain in cats using behavioral indices.

Pain was assessed 12 hours prior to surgery (baseline; BL), and 0.5, 1, 2, 4, 8, 12, 18, and 24 hours after extubation, using the Glasgow feline composite measure pain scale24 (CMPS-Feline; 0, no pain; 20, maximum pain), and the UNESP-Botucatu multidimensional composite pain scale25 (UFEPS; 0, no pain; 24, maximum pain). The CMPS-Feline included behavioral categories (scale range = 0 to16 points) and facial expression changes (scale range = 0 to 4 points), while the UFEPS was based on 2 domains (pain expression, scale range = 0 to 12 points; psychomotor change, scale range = 0 to 12 points). Rescue analgesia was provided with morphine (0.2 mg/kg [0.09 mg/lb]; IM) if the CMPS-Feline score was ≥ 5/20, or the UFEPS score was ≥ 6/24. The number of cats requiring rescue analgesia and the number of additional administrations of tramadol and/or meloxicam were recorded.

The degree of sedation was scored at the same time points according to a descriptive numerical scale (ranged from 0 to 16 points),26 based on 5 criteria: spontaneous posture, response to noise (handclap) and noxious stimulus (pressure to a hind paw digit), resistance to being placed in lateral recumbency, and mandibular tone. The degree of sedation was classified as poor (score 0 to 4), clinical (score 5 to 13), or profound (score > 13).

Surgical wound inflammation

Wound inflammation was scored at the same time points, with the exception of baseline, using a numerical rating scale (0 to 3 points), where 0 = no edema, erythema; 1 = slight edema/erythema at any wound site; 2 = overall slight edema/erythema; 3 = marked edema/erythema.27

Laboratory data

Blood samples were collected from the jugular vein (3 mL) for complete blood count (into EDTA), serum clinical biochemistry (no anticoagulant), and the coagulation test (into 3.18% sodium citrate) at baseline (24 hours prior to the surgery) and 24 hours post-extubation. Biochemistry variables included blood urea nitrogen (BUN), creatinine, γ-glutamyltransferase (GGT), and alkaline phosphatase (ALP). Blood clotting was measured by the prothrombin time test (PT), using a commercial kit (Celer Wondfo; Celer Biotecnologia SA). Fecal samples were collected at the same time points to detect the presence of occult blood, using the benzidine test (Benzidine PA 10 g; Exodo Científica).

Outcome measures

The primary outcome measures were the assessment of pain and wound inflammation, and the requirement for the rescue analgesia. Secondary outcome measures included sedation scores and laboratorial data.

Statistical analysis

A sample size of at least 15 cats per group was estimated to achieve 80% statistical power, at an overall α level of 0.05 to detect a prevalence of postoperative treatment failure (considered as need for rescue analgesia) of 70% in the PG and 20% in the BG. The sample calculation was based on pilot data. A Shapiro-Wilk test was performed to assess the normality of the variables. Data are expressed as mean ± SD (parametric variables) or median (range) (nonparametric variables), as appropriate. Body weight, age, dose of propofol, procedural times and laboratorial data were compared between groups using the unpaired t-test.

After receiving the first dose of rescue analgesia cats were removed from the statistical analysis of pain scores. Corresponding AUCs of CMPS-Feline and UFEPS were calculated from baseline until 24 hours using the trapezoidal method and compared between groups. A Mann-Whitney U-test was used to compare pain, sedation, and inflammation scores between groups and the number of morphine doses administered to the groups. A Friedman test was used to compare differences in pain, sedation, and inflammation scores over time within each group. The number of cats requiring perioperative rescue analgesia was compared between groups using the Fisher exact test. A Kaplan-Meier survival analysis was used to describe the percentage of rescue analgesia required at different time points in the postoperative period. Laboratorial data were analyzed using ANOVA with the F test followed by the Tukey test to compare differences between treatments, differences in time for each treatment, and interaction between treatment and time. All analyses were performed using GraphPad Prism 7.0. Differences were considered significant when P < .05.

Results

From the 36 cats initially enrolled in the study, 6 were excluded due to lactation (n = 3) or aggressive behavior (3).

There were no significant differences between groups in age, body weight, dose of propofol, duration of anesthesia and surgery, and time to extubation (P > .05). Recovery time was significantly faster in the BG (P = .002; Table 1). The mean values ± SD of the interval time between bromelain administration and the postoperative time points (0.5 to 24 hours) were: 131 ± 2 minutes (0.5h), 161 ± 2 minutes (1h), 220 ± 2.5 minutes (2h), 340 ± 2.5 minutes (4h), 580 ± 3 minutes (8h), 820 ± 3.5 minutes (12h), 1180 ± 3 minutes (18h), 1541 ± 3 minutes (24h).

Table 1

Demographic data and procedural times recorded in cats undergoing ovariohysterectomy treated with oral bromelain suspension (BG; n = 15) or placebo solution (PG; 15).

Variable BG (n = 15) PG (n =15) P value
Body weight (kg) 3.0 ± 0.6 2.9 ± 0.5 .78
Surgery time (min) 10.7 ± 1.9 10.4 ± 2.1 .72
Anesthesia time (min) 29.8 ± 2.0 29.6 ± 2.3 .80
Time to extubation (min) 6.7 ± 1.7 8.0 ± 2.3 .10
Time to recovery (min) 19.6 ± 6* 32.1 ± 12 .002

Bromelain (40 mg/kg [18 mg/lb]; PO) or placebo (0.1 mL/kg [0.045 mL/lb]; PO) were administered 90 minutes before and 12 hours after surgery.

Data are presented as mean ± SD. Values of P < .05 were considered significant.

*Significantly different from PG (unpaired t test).

Pain scores did not differ between groups. The AUC recorded for UFEPS in the BG and PG was 55 ± 23 and 54 ± 11, respectively, and for CMPS-Feline was 57 ± 25 and 58 ± 9, respectively (P = .87 to .89). Compared with baseline values, UFEPS scores were increased from 0.5 to 8 hours and 0.5 to 4 hours in the BG and PG, respectively (P < .001), while CMPS-Feline scores were increased only at 2 and 4 hours in the BG and PG, respectively (P < .0001; Figure 1). Lower sedation scores were recorded in the BG at 0.5 and at 1-hour post-extubation compared to the PG (P < .0001). Compared to the corresponding baseline values, sedation scores were significantly increased from 0.5 to 1 hour in both treatment groups (P < .0001). The degree of inflammation/edema did not differ between groups or over time.

Figure 1
Figure 1

Pain (A, B), sedation (C), and inflammation (D) scores measured prior to anesthesia (baseline [BL]) and for up to 24 hours after extubation in cats undergoing ovariohysterectomy treated with oral bromelain suspension (BG; n = 15) or placebo solution (PG; 15). Bromelain (40 mg/kg [18 mg/lb]; PO) or placebo (0.1 mL/kg [0.045 mL/lb]; PO) were administered 90 minutes before and 12 hours after surgery. Pain, sedation, and inflammation scores were assessed by a single observer at the indicated time points. Pain was assessed using the Glasgow feline composite measure pain scale (CMPS-Feline; 0, no pain; 20, maximum pain), and the UNESP-Botucatu multidimensional composite pain scale (UFEPS; 0, no pain; 24, maximum pain). Sedation degree was scored according to a descriptive numerical scale (ranged from 0 to 16 points; 0, no sedation; 16, maximum sedation). Surgical wound inflammation was scored using a numerical rating scale (0 to 3 points), where 0 = no edema, erythema; 1 = slight edema/erythema at any wound site; 2 = overall slight edema/erythema; 3 = marked edema/erythema. Data are presented as median (range). *Significantly different from BL values (Friedman test, P < .0001); †Significantly different from PG (Mann-Whitney test, P < .0001). Values of P < .05 were considered significant.

Citation: Journal of the American Veterinary Medical Association 261, 9; 10.2460/javma.23.02.0117

The number of cats requiring rescue analgesia and the number of total rescue analgesic interventions during the study-period did not differ between groups (P = .28 to .46). Rescue analgesia was given in 33.3% (5/15) and 53.3% (8/15) of the cats in the BG and PG, respectively. All cats received only a single dose of morphine at different time points (Table 2). The Kaplan–Meier curve did not show significant differences between groups (log-rank test, P = .28; Figure 2).

Table 2

Summary of rescue analgesia data recorded for 24 hours after ovariohysterectomy in cats treated with oral BG (n = 15) or PG (15).

Group Postoperative time (h) Rescue doses Rescued cats Nonrescued cats
0.5 1 2 4 8 12 18 24
BG 0 0 1 1 3 0 0 0 5 5/15 10/15
PG 0 0 2 2 2 1 1 0 8 8/15 7/15

Rescue analgesia was provided with morphine (0.2 mg/kg [0.09 mg/lb]; IM) if the Glasgow feline composite measure pain scale score was ≥ 5/20, or the UNESP-Botucatu multidimensional composite pain scale score was ≥ 6/24. Values of P < .05 were considered significant.

See Table 1 for remainder of key.

Differences between groups were not significant (P = .28 to .46).

Figure 2
Figure 2

Kaplan-Meier survival curve for time to rescue analgesia (ie, no rescue analgesia needed) during 24 hours following ovariohysterectomy in cats treated with oral BG (n = 15) or PG (15). Rescue analgesia was provided with morphine (0.2 mg/kg [0.09 mg/lb]; IM) if the CMPS-Feline score was ≥ 5 of 20, or the UFEPS score was ≥ 6 of 24. After receiving the first dose of rescue analgesia cats were removed from the statistical analysis of pain scores. See Figure 1 for reminder of key. Differences between groups were not significant (P = .28)

Citation: Journal of the American Veterinary Medical Association 261, 9; 10.2460/javma.23.02.0117

Fecal occult blood was detected in 26.6% (4/15) and 6.6% (1/15) of cats in the BG and PG, respectively (P = .32). Lower concentrations of creatinine and GGT were identified in the BG compared to PG (P = .005 to .0001). Compared to corresponding baseline values, BUN, creatinine, GGT, and ALP levels were decreased at 24 hours in the BG (P = .04 to .0004), while the PT did not differ between groups (P = .53) or over time (P = .10; Table 3). No other effects were observed in the recovery period.

Table 3

Mean ± SD values for BUN, creatinine, GGT, ALP, and prothrombin time (PT) measured in cats undergoing ovariohysterectomy treated with oral BG (n = 15) or PG (15).

Variable Group
BG (n =15) PG (n =15)
BL 24 hours BL 24 hours
BUN (mg/dL) 55 ± 7 51 ± 7* 51 ± 8 53 ± 6
Creatinine (mg/dL) 1.1 ± 0.13 0.8 ± 0.13*† 1.1 ± 0.13 1.1 ± 0.11
GGT (U/L) 4.7 ± 1 3.5 ± 0.9*† 4.4 ± 1 4.6 ± 1
ALP (U/L) 70 ± 16 61 ± 11* 62 ± 19 65 ± 13
PT (sec) 9 ± 0.8 9.3 ± 0.6 9 ± 1 9.6 ± 0.8

Blood samples were collected from the jugular vein (3 mL) for serum clinical biochemistry, and the coagulation test at baseline (BL = 24 hours prior to the surgery) and 24 hours after extubation. Biochemistry variables included BUN, creatinine, GGT, and ALP. Blood clotting was measured by the PT test. See Table 1 for remainder of key.

*Significantly different from baseline values (P < .0001). †Significantly different from PG (P < .0001). Values of P < .05 were considered significant.

Discussion

The current study demonstrated no significant effects of bromelain over placebo on postoperative pain or surgical wound inflammation in healthy cats undergoing ovariohysterectomy. Therefore, our hypothesis that bromelain would improve analgesia and reduce inflammation compared to the control treatment was incorrect.

These results are in contrast with previous human clinical reports that found significant analgesic and anti-inflammatory effects when administering bromelain during the perioperative period in patients undergoing oral and periodontal surgeries.20,28,29 Although the comparison of data obtained from different species is not recommended, the discrepancy between these results may be attributed to the different surgical procedures performed in the human studies, where the patients underwent third molar extraction and probably experienced a higher degree of inflammation and edema compared with the cats of our study, since ovariohysterectomy is a surgical procedure of soft tissues which induces weak to moderate degrees of pain and inflammatory responses.27 In addition, different from veterinary patients, humans can verbally express the presence of pain and rate its severity, which is more accurate than pain assessments based on behavior changes, as performed in our study.

This was the first clinical report to investigate postoperative analgesic and anti-inflammatory effects of bromelain in small animal practice. Therefore, some aspects of the experimental design may have contributed to the apparent lack of a significant treatment effect of bromelain over placebo. The optimal therapeutic dosages of bromelain are not well established. Data from animal models of inflammation suggest a dose-dependent effect of bromelain, with greater inhibition of edema provided by the administration of higher dosages.30,31 On the other hand, a recent study showed minor antinociceptive effects when bromelain was orally administered at high dosages compared with lower dosages in mice.14 In our protocol, we chose an intermediate bromelain dosage, based on previous studies conducted in rats that reported dosages ranging from 25 to 300 mg/kg [11 to 136 mg/lb], PO.11,14,30 The interval of administration of 12 hours was based on clinical reports that investigated the analgesic and anti-inflammatory effects of bromelain in oral surgeries in human patients.28,32 Nevertheless, it is possible that this bromelain dosage regimen was not sufficient to achieve effective plasma concentrations, because there is no information regarding its bioavailability in cats. Future bioavailability studies are needed to analyze the plasma concentration of bromelain at key time points and confirm its ideal therapeutic level in cats. Moreover, in our study the bromelain was derived from pineapple stem. Although most commercially available bromelain preparations contain predominantly stem bromelain,6,14 decreased proteinase activity has been demonstrated in these formulations when compared to fruit bromelain,33 which may interfere in the systemic effects. Therefore, it is possible that the quantities of protease in the bromelain formulation used in the present study were insufficient to provide analgesia. Additional studies are needed to clarify the impact of the bromelain preparation on the clinical effects.

The lack of significant intergroup changes in the pain scores might also be attributed to the insensitivity of the measurement scales, or bias. Although UFEPS and CMPS-Feline are reliable and validated methods for pain assessment in cats, both scoring systems may be biased by the effects of drugs administered in the anesthetic protocol. In the current study, meperidine was administered as pre-medication due to its short duration of action (60 to 90 minutes),34 to avoid interfering in pain scores during the early postoperative period. However, it is possible that the residual sedative effects of anesthesia may have masked pain behaviors, affecting both UFEPS and CMPS-Feline scores. Additionally, to avoid interobserver variability and to improve the sensitivity of both pain assessment tools used in the present study, postoperative measurements were performed by a single observer, with previous experience in feline pain assessments. However, given the subjectivity of pain signs, even an experienced observer may misclassify a patient with pain as not having pain, inducing bias in the evaluation of analgesic efficacy. Our data showed that almost 50% of the placebo-treated cats did not receive rescue analgesia, suggesting a possible failure in pain recognition. Moreover, in the present study all surgeries were performed by an experienced surgeon using the minimally invasive laparotomy technique, which probably contributed to a decreased inflammatory response in the surgical wound, as well as reduced postoperative discomfort in all the cats. Therefore, the low pain-scale sensitivity coupled with procedures that may not produce severe enough pain may make it difficult to detect the efficacy of bromelain.

On the other hand, both UFEPS and CMPS-Feline scales were enough sensitivity to detected significant differences within groups over time. Consistent with previous studies that demonstrated that the peak of pain following feline ovariohysterectomy is expected after 2 and 4 hours,3539 our data showed that in comparison with the baseline values, CMPS-Feline scores were increased at 2 and 4 hours in the BG and PG, respectively, while based on the UFEPS, higher pain scores were recorded at from 0.5 to 4 hours in the PG, and from 0.5 to 8 hours in the BG. Increased pain scores and acute inflammation are expected until 24 hours after surgery, due to the peripheral sensitization induced by the tissue trauma.40

When considering postoperative analgesic requirements, more cats in the PG received rescue analgesia than in the BG, but differences were not significant. Rescue analgesia was required in 33.3% (5/15) of the bromelain-treated cats, and in 53.3% (8/15) of the placebo-treated cats, which are values close to the prevalence of 35% to 50% reported by previous studies conducted in cats undergoing ovariohysterectomy receiving different opioids preoperatively.3537 In view of this, at the dosage and frequency administered in the current study, stem bromelain did not confer any benefit in postoperative pain relief over the opioid-based analgesia.

The dosage regimen used in this study seemed to be clinically safe, since minimal adverse effects were recorded during the 24 hours-period. Data from animal studies have demonstrated that bromelain has low systemic toxicity, with a lethal dose greater than 10 g/kg [4.5 g/lb].8,41 Nevertheless, the inclusion of bromelain in the anesthetic protocol increased the prevalence of positive tests for fecal occult blood, although intergroup differences were not significant. Like NSAIDs, bromelain also inhibits COX-2 enzyme, decreasing prostaglandin E2 levels,11 which could lead to gastrointestinal irritation, justifying the presence of occult fecal blood in 26.6% (4/15) of the cats in the BG. On the other hand, this gastrointestinal effect could also be attributed to blood clotting alterations, since previous studies have demonstrated anticoagulant effects in rats treated orally with bromelain.12,13 However, our findings showed similar prothrombin times between groups, with no significant differences in comparison with pre-treatment values, suggesting that bromelain probably did not affect blood clotting. A similar finding was reported previously in human patients, where oral treatment with bromelain had no significant effects on bleeding, coagulation, and prothrombin time.18

With regards to serum clinical biochemistry, our data demonstrated no significant differences between groups in the preoperative analysis, with all variables within normal limits for healthy cats. Nonetheless, significant decreases were found 24 hours after bromelain treatment in BUN, creatinine, ALP, and GGT levels in comparison with baseline values. Furthermore, our results showed significant intergroup differences post-treatment, with lower serum creatinine and GGT detected in the BG. Data from previous studies have reported beneficial effects of bromelain administration in animal models of renal and hepatic failure.4244 In gentamicin-induced nephrotoxity in rats, treatment with peptides derived from bromelain hydrolyses decreased serum concentrations of BUN and creatinine, which was attributed to antioxidant effects and also to the increase in the glomerular filtration rate.42 Another study in rats reported that intraperitoneal administration of a mixture of protease enzymes (bromelain, trypsin, and rutoside) ameliorated the progression of renal disease and significantly reduced creatinine levels, due to increased creatinine clearance.44 A similar tendency was found in animal models of ischemia/reperfusion, where intravenous administration of low doses of bromelain improved hepatic microcirculation and reduced liver enzymes.43 In view of these data, it is possible that the results found in our study may also be associated with an increase in renal and hepatic circulation, which could justify the decrease in all serum biochemistry variables after bromelain treatment. Interestingly, in the current study lower sedation scores were recorded in the BG from 0.5 to 1 hour, which probably contributed to the significantly shorter post-anesthetic recovery time in this group. These results might also be related to an increase in renal and hepatic circulation, contributing to anesthetic drug metabolism and elimination. Additional studies are needed to better clarify the renal and hepatic effects of bromelain in cats.

The design of the current study has some limitations. The small sample size may have masked significant differences between groups. The study population was estimated considering a prevalence of postoperative analgesic supplementation of 70% and 20% in the PG and BG, respectively. Nevertheless, the intergroup differences were smaller than this, limiting the statistical power of our study. Additionally, to avoid the interference of rescue analgesia in the pain assessments, the cats that received morphine during the postoperative period were removed from comparisons of pain scores, resulting in unequal group sizes, which may also have limited the analyses. Although in the current study relevant adverse effects were not detected at the dosage of bromelain administered, the inclusion of additional diagnostic methods, such as endoscopy, mucosal biopsy, and other tests of blood coagulation (eg, activated partial thromboplastin, serum plasmin concentration) could contribute to better elucidation of the effects of bromelain on the digestive system and blood coagulation. Another important limitation of this study is the absence of a pharmacokinetic profile of bromelain, which is pivotal to clarify the time to peak plasma concentration, and terminal half-life of this proteolytic enzyme in cats.

Bromelain did not provide significant postoperative benefits over placebo, in terms of pain and surgical wound inflammation, in healthy cats undergoing ovariohysterectomy. Further studies are needed to better elucidate the renal and hepatic effects of bromelain as well as to investigate the optimal dosage of bromelain along with its pharmacokinetic profile in cats.

Acknowledgments

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) – Finance Code 001.

The authors have nothing to declare.

References

  • 1.

    Shih AC, Robertson S, Isaza N, Pablo L, Davies W. Comparison between analgesic effects of buprenorphine, carprofen, and buprenorphine with carprofen for canine ovariohysterectomy. Vet Anaesth Analg. 2008;35(1):6979. doi:10.1111/j.1467-2995.2007.00352.x

    • Search Google Scholar
    • Export Citation
  • 2.

    Steagall PV, Taylor PM, Rodrigues LC, Ferreira TH, Minto BW, Aguiar AJ. Analgesia for cats after ovariohysterectomy with either buprenorphine or carprofen alone or in combination. Vet Rec. 2009;164(12):359363. doi:10.1136/vr.164.12.359

    • Search Google Scholar
    • Export Citation
  • 3.

    Staffieri F, Centonze P, Gigante G, De Pietro L, Crovace A. Comparison of the analgesic effects of robenacoxib, buprenorphine and their combination in cats after ovariohysterectomy. Vet J. 2013;197(2):363367. doi:10.1016/j.tvjl.2013.01.018

    • Search Google Scholar
    • Export Citation
  • 4.

    Lascelles BD, Court MH, Hardie EM, Robertson SA. Nonsteroidal anti-inflammatory drugs in cats: a review. Vet Anaesth Analg. 2007;34(4):228250. doi:10.1111/j.1467-2995.2006.00322.x

    • Search Google Scholar
    • Export Citation
  • 5.

    McLean MK, Khan SA. Toxicology of frequently encountered nonsteroidal anti-inflammatory drugs in dogs and cats: an update. Vet Clin North Am Small Anim Pract. 2018;48(6):969984. doi:10.1016/j.cvsm.2018.06.003

    • Search Google Scholar
    • Export Citation
  • 6.

    Agrawal P, Nikhade P, Patel A, Mankar N, Sedani S. Bromelain: a potent phytomedicine. Cureus. 2022;14(8):e27876.

  • 7.

    MacKichan C, Ruthman J. Herbal product use and perioperative patients. AORN J. 2004;79(5):948959. doi:10.1016/S0001-2092(06)60726-6

  • 8.

    Taussig SJ, Batkin S. Bromelain, the enzyme complex of pineapple (Ananas comosus) and its clinical application. An update. J Ethnopharmacol. 1988;22(2):191203. doi:10.1016/0378-8741(88)90127-4

    • Search Google Scholar
    • Export Citation
  • 9.

    Lotz-Winter H. On the pharmacology of bromelain: an update with special regard to animal studies on dose-dependent effects. Planta Med. 1990;56(3):249253. doi:10.1055/s-2006-960949

    • Search Google Scholar
    • Export Citation
  • 10.

    de A C Almeida R, de Sousa Lima FCM, do E Vasconcelos BC. Is bromelain an effective drug for the control of pain and inflammation associated with impacted third molar surgery? Systematic review and meta-analysis. Int J Oral Maxillofac Implants. 2019;48(5):651658. doi:10.1016/j.ijom.2018.07.028

    • Search Google Scholar
    • Export Citation
  • 11.

    Bakare AO, Owoyele BV. Bromelain reduced pro-inflammatory mediators as a common pathway that mediate antinociceptive and anti-anxiety effects in sciatic nerve ligated Wistar rats. Sci Rep. 2021;11(1):289. doi:10.1038/s41598-020-79421-9

    • Search Google Scholar
    • Export Citation
  • 12.

    Errasti ME, Prospitti A, Viana CA, et al. Effects on fibrinogen, fibrin, and blood coagulation of proteolytic extracts from fruits of Pseudananas macrodontes, Bromelia balansae, and B. hieronymi (Bromeliaceae) in comparison with bromelain. Blood Coagul Fibrinolysis. 2016;27(4):441449. doi:10.1097/MBC.0000000000000531

    • Search Google Scholar
    • Export Citation
  • 13.

    Livio M, De Gaetano G, Donati MB. Effect of bromelain on fibrinogen level, prothrombin complex and platelet aggregation in the rat - a preliminary report. Drugs Exp Clin Res. 1978;1:4953.

    • Search Google Scholar
    • Export Citation
  • 14.

    Orlandi-Mattos PE, Aguiar RB, da Silva Vaz I, et al. Enkephalin related peptides are released from jejunum wall by orally ingested bromelain. Peptides. 2019;115:3242. doi:10.1016/j.peptides.2019.02.008

    • Search Google Scholar
    • Export Citation
  • 15.

    Gläser D, Hilberg T. The influence of bromelain on platelet count and platelet activity in vitro. Platelets. 2006;17(1):3741. doi:10.1080/09537100500197489

    • Search Google Scholar
    • Export Citation
  • 16.

    Metzig C, Grabowska E, Eckert K, Rehse K, Maurer HR. Bromelain proteases reduce human platelet aggregation in vitro, adhesion to bovine endothelial cells and thrombus formation in rat vessels in vivo. In Vivo. 1999;13(1):712.

    • Search Google Scholar
    • Export Citation
  • 17.

    Kaur H, Corscadden K, Lott C, Elbatarny HS, Othman M. Bromelain has paradoxical effects on blood coagulability: a study using thromboelastography. Blood Coagul Fibrinolysis. 2016;27(7):745752. doi:10.1097/MBC.0000000000000244

    • Search Google Scholar
    • Export Citation
  • 18.

    Cirelli MG, Smyth RD. Effects of bromelain anti-edema therapy on coagulation, bleeding, and prothrombin times. J New Drugs. 1963;3(1):3739. doi:10.1002/j.1552-4604.1963.tb00060.x

    • Search Google Scholar
    • Export Citation
  • 19.

    Eckert K, Grabowska E, Stange R, Schneider U, Eschmann K, Maurer HR. Effects of oral bromelain administration on the impaired immunocytotoxicity of mononuclear cells from mammary tumor patients. Oncol Rep. 1999;6(6):11911199. doi:10.3892/or.6.6.1191

    • Search Google Scholar
    • Export Citation
  • 20.

    Tan Y, Li P. Bromelain has significant clinical benefits after extraction of the third molar during chemotherapy in patients with hematologic tumor. Oncol Lett. 2018;15(3):29622966.

    • Search Google Scholar
    • Export Citation
  • 21.

    Seltzer AP. Minimizing post-operative edema and ecchymoses by the use of an oral enzyme preparation (bromelain). A controlled study of 53 rhinoplasty cases. Eye Ear Nose Throat Mon. 1962;41:813817.

    • Search Google Scholar
    • Export Citation
  • 22.

    Golezar S. Ananas comosus Effect on perineal pain and wound healing after episiotomy: a randomized double-blind placebo-controlled clinical trial. Iran Red Crescent Med J. 2016;18(3):e21019. doi:10.5812/ircmj.21019

    • Search Google Scholar
    • Export Citation
  • 23.

    Spaeth GL. The effect of bromelains on the inflammatory response caused by cataract extraction: a double-blind study. Eye Ear Nose Throat Mon. 1968;47(12):634639.

    • Search Google Scholar
    • Export Citation
  • 24.

    Reid J, Scott EM, Calvo G, Nolan AM. Definitive Glasgow acute pain scale for cats: validation and intervention level. Vet Rec. 2017;180(18):449. doi:10.1136/vr.104208

    • Search Google Scholar
    • Export Citation
  • 25.

    Brondani JT, Mama KR, Luna SP, et al. Validation of the English version of the UNESP-Botucatu multidimensional composite pain scale for assessing postoperative pain in cats. BMC Vet Res. 2013;9(1):143. doi:10.1186/1746-6148-9-143

    • Search Google Scholar
    • Export Citation
  • 26.

    Ravasio G, Gallo M, Beccaglia M, et al. Evaluation of a ketamine-propofol drug combination with or without dexmedetomidine for intravenous anesthesia in cats undergoing ovariectomy. J Am Vet Med Assoc. 2012;241(10):13071313. doi:10.2460/javma.241.10.1307

    • Search Google Scholar
    • Export Citation
  • 27.

    Benito-de-la-Víbora J, Lascelles BD, García-Fernández P, Freire M, de Segura IA. Efficacy of tolfenamic acid and meloxicam in the control of postoperative pain following ovariohysterectomy in the cat. Vet Anaesth Analg. 2008;35(6):501510. doi:10.1111/j.1467-2995.2008.00407.x

    • Search Google Scholar
    • Export Citation
  • 28.

    Ordesi P, Pisoni L, Nannei P, Macchi M, Borloni R, Siervo S. Therapeutic efficacy of bromelain in impacted third molar surgery: a randomized controlled clinical study. Quintessence Int. 2014;45(8):679684.

    • Search Google Scholar
    • Export Citation
  • 29.

    Majid OW, Al-Mashhadani BA. Perioperative bromelain reduces pain and swelling and improves quality of life measures after mandibular third molar surgery: a randomized, double-blind, placebo-controlled clinical trial. J Oral Maxillofac Surg. 2014;72(6):10431048. doi:10.1016/j.joms.2013.12.035

    • Search Google Scholar
    • Export Citation
  • 30.

    Pirotta F, de Giuli-Morghen C. Bromelain: anti-inflammatory and serum fibronolytic activity after oral administration in the rat. Drugs Exp Clin Res. 1978;4:120.

    • Search Google Scholar
    • Export Citation
  • 31.

    Vellini M, Desideri D, Milanese A, et al. Possible involvement of eicosanoids in the pharmacological action of bromelain. Arzneimittelforschung. 1986;36(1):110112.

    • Search Google Scholar
    • Export Citation
  • 32.

    Singh T, More V, Fatima U, Karpe T, Aleem MA, Prameela J. Effect of proteolytic enzyme bromelain on pain and swelling after removal of third molars. J Int Soc Prev Community Dent. 2016;6(9; suppl 3):S197S204. doi:10.4103/2231-0762.197192

    • Search Google Scholar
    • Export Citation
  • 33.

    Hale LP, Greer PK, Trinh CT, James CL. Proteinase activity and stability of natural bromelain preparations. Int Immunopharmacol. 2005;5(4):783793. doi:10.1016/j.intimp.2004.12.007

    • Search Google Scholar
    • Export Citation
  • 34.

    Yang NY, Ko JC, Wang HC, Liu PC. A preliminary study comparing the sedative, cardiorespiratory, and histaminic-releasing effects of intramuscular and intravenous administration of pethidine (meperidine) with midazolam in healthy cats. Vet Anim Sci. 2021;14:100218. doi:10.1016/j.vas.2021.100218

    • Search Google Scholar
    • Export Citation
  • 35.

    Brondani JT, Loureiro Luna SP, Beier SL, Minto BW, Padovani CR. Analgesic efficacy of perioperative use of vedaprofen, tramadol or their combination in cats undergoing ovariohysterectomy. J Feline Med Surg. 2009;11(6):420429. doi:10.1016/j.jfms.2008.10.002

    • Search Google Scholar
    • Export Citation
  • 36.

    Marques VI, Cassu RN, Nascimento FF, et al. Laser acupuncture for postoperative pain management in cats. Evid Based Complement Alternat Med. 2015;2015:653270. doi:10.1155/2015/653270

    • Search Google Scholar
    • Export Citation
  • 37.

    Evangelista MC, Silva RA, Cardozo LB, et al. Comparison of preoperative tramadol and pethidine on postoperative pain in cats undergoing ovariohysterectomy. BMC Vet Res. 2014;10(1):252. doi:10.1186/s12917-014-0252-1

    • Search Google Scholar
    • Export Citation
  • 38.

    Benito J, Monteiro B, Lavoie AM, Beauchamp G, Lascelles BDX, Steagall PV. Analgesic efficacy of intraperitoneal administration of bupivacaine in cats. J Feline Med Surg. 2016;18(11):906912. doi:10.1177/1098612X15610162

    • Search Google Scholar
    • Export Citation
  • 39.

    Steagall PV, Benito J, Monteiro BP, Doodnaught GM, Beauchamp G, Evangelista MC. Analgesic effects of gabapentin and buprenorphine in cats undergoing ovariohysterectomy using two pain-scoring systems: a randomized clinical trial. J Feline Med Surg. 2018;20(8):741748. doi:10.1177/1098612X17730173

    • Search Google Scholar
    • Export Citation
  • 40.

    Lemke KA. Understanding the pathophysiology of perioperative pain. Can Vet J. 2004;45(5):405413.

  • 41.

    Moss JN, Frazier CV, Martin GJ. Bromelains. The pharmacology of the enzymes. Arch Int Pharmacodyn Ther. 1963;145:166189.

  • 42.

    Sebekova K, Paczek L, Dämmrich J, et al. Effects of protease therapy in the remnant kidney model of progressive renal failure. Miner Electrolyte Metab. 1997;23(3-6):291295.

    • Search Google Scholar
    • Export Citation
  • 43.

    Bahde R, Palmes D, Minin E, et al. Bromelain ameliorates hepatic microcirculation after warm ischemia. J Surg Res. 2007;139(1):8896. doi:10.1016/j.jss.2006.10.004

    • Search Google Scholar
    • Export Citation
  • 44.

    Hidayat M, Prahastuti S, Riany DU, et al. Kidney therapeutic potential of peptides derived from the bromelain hydrolysis of green peas protein. Iran J Basic Med Sci. 2019;22(9):10161025.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 173 0 0
Full Text Views 2232 1849 116
PDF Downloads 1615 1262 53
Advertisement