Efficacy of intravenous administration of apomorphine for removal of gastric foreign material in dogs: 495 cases (2010–2015)

Kevin S. Kirchofer 1Ocean State Veterinary Specialists, 1480 S County Trail, East Greenwich, RI 02818.

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Gary Block 1Ocean State Veterinary Specialists, 1480 S County Trail, East Greenwich, RI 02818.

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Justine A. Johnson 1Ocean State Veterinary Specialists, 1480 S County Trail, East Greenwich, RI 02818.
1Ocean State Veterinary Specialists, 1480 S County Trail, East Greenwich, RI 02818.

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Abstract

OBJECTIVE

To evaluate the efficacy of IV administration of apomorphine for removal of gastric foreign bodies in dogs.

ANIMALS

495 dogs with gastric foreign bodies.

PROCEDURES

Records of a veterinary hospital were searched to identify dogs that received an injectable formulation of apomorphine between January 1, 2010, and July 30, 2015. Dogs with a gastric foreign body that received an IV injection of apomorphine were included in the study. Information extracted from the record of each dog included signalment, type of foreign material ingested, duration between foreign material ingestion and emesis, dose and number of doses of apomorphine administered, and whether emesis occurred and did or did not result in successful removal of the foreign body. Descriptive data were compared between dogs with and without successful foreign body removal.

RESULTS

Emesis with successful foreign body removal was achieved in 363 and 11 dogs after administration of 1 and 2 doses of apomorphine, respectively. Successful removal was more likely for young dogs and dogs that had ingested fabric, leather, or bathroom waste. Successful removal was less likely as the duration between foreign body ingestion and emesis increased and for dogs that received opioids, sedatives, or antiemetics before apomorphine administration. Minor adverse effects were recorded for only 4 dogs.

CONCLUSIONS AND CLINICAL RELEVLANCE

IV administration of apomorphine was a viable alternative for induction of emesis and removal of gastric foreign bodies in dogs. Dogs should be examined as soon as possible after foreign body ingestion and should not receive any medications that might affect apomorphine efficacy.

Abstract

OBJECTIVE

To evaluate the efficacy of IV administration of apomorphine for removal of gastric foreign bodies in dogs.

ANIMALS

495 dogs with gastric foreign bodies.

PROCEDURES

Records of a veterinary hospital were searched to identify dogs that received an injectable formulation of apomorphine between January 1, 2010, and July 30, 2015. Dogs with a gastric foreign body that received an IV injection of apomorphine were included in the study. Information extracted from the record of each dog included signalment, type of foreign material ingested, duration between foreign material ingestion and emesis, dose and number of doses of apomorphine administered, and whether emesis occurred and did or did not result in successful removal of the foreign body. Descriptive data were compared between dogs with and without successful foreign body removal.

RESULTS

Emesis with successful foreign body removal was achieved in 363 and 11 dogs after administration of 1 and 2 doses of apomorphine, respectively. Successful removal was more likely for young dogs and dogs that had ingested fabric, leather, or bathroom waste. Successful removal was less likely as the duration between foreign body ingestion and emesis increased and for dogs that received opioids, sedatives, or antiemetics before apomorphine administration. Minor adverse effects were recorded for only 4 dogs.

CONCLUSIONS AND CLINICAL RELEVLANCE

IV administration of apomorphine was a viable alternative for induction of emesis and removal of gastric foreign bodies in dogs. Dogs should be examined as soon as possible after foreign body ingestion and should not receive any medications that might affect apomorphine efficacy.

Apomorphine is a centrally acting nonselective dopamine agonist often used in dogs to induce vomiting for the removal of toxicants or foreign material from the gastrointestinal tract.1,2 It produces vomiting by direct stimulation of dopamine D2 receptors in the medullary chemoreceptor trigger zone.3,4 Apomorphine is an effective emetic in dogs. In 1 study,5 apomorphine administration resulted in emesis in 59 of 63 (94%) dogs that had ingested toxic agents, and the mean percentage recovery of ingested toxic agents in the vomitus of those dogs was 52%. Dogs often ingest nonfood materials that are not toxicants (ie, foreign bodies) but can lead to physical obstruction of the gastrointestinal tract,6–8 and approximately 16% to 50% of foreign bodies in dogs are located in the stomach rather than other areas of the gastro-intestinal tract at initial examination.7,9 In such dogs, apomorphine is frequently administered initially to induce emesis in an attempt to remove the foreign body and obviate the need for more invasive and expensive procedures, such as endoscopy or surgery, for foreign body removal.

In a retrospective study by Cote et al,10 use of an apomorphine ocular insert (apomorphine concentration, 2 mg/insert) successfully induced emesis and removal of an ingested foreign body in 492 of 596 (82.6%) dogs. However, only a fixed dose of apomorphine can be administered by means of an ocular insert, and the drug in the insert has to be absorbed through the conjunctiva and enter the circulation before it exerts any effects. Injectable administration of apomorphine allows the drug to be accurately dosed on the basis of patient body weight, and therapeutic blood concentrations of the drug can be rapidly achieved when it is administered as an IV bolus. In the Cote et al study,10 29 of 32 (90.6%) dogs vomited at a median of 1 minute after receiving an IV injection of apomorphine (0.03 mg/kg [0.014 mg/lb]), but information regarding the reason (ingestion of toxicant or a foreign body) apomorphine was administered to those dogs was not provided.

Studies regarding the effectiveness of IV administration of apomorphine to induce emesis for removal of gastric foreign bodies in dogs are lacking. The purpose of the study reported here was to evaluate the efficacy of IV administration of apomorphine for removal of gastric foreign bodies in dogs and to identify factors that affect that efficacy.

Materials and Methods

Case selection criteria

The medical record database of a 24-hour emergency and referral veterinary hospital was searched to identify dogs that received an injectable apomorphine formulation between January 1, 2010, and July 30, 2015. Dogs with a gastric foreign body that received an IV injection of apomorphine were included in the study. Diagnosis of a gastric foreign body was made on the basis of owner observation of the dog ingesting foreign material or evidence of foreign material in the stomach as determined by diagnostic imaging. Dogs that received apomorphine following ingestion of a toxicant were not included in the study.

Medical records review

For each dog eligible for study inclusion, data extracted from the medical records included signalment (breed, age, sex, and body weight), duration between foreign body ingestion and apomorphine administration, type of material ingested, information regarding administration of any other medications that might affect apomorphine efficacy, dose of apomorphine administered, and whether additional doses of apomorphine were administered. Other information collected included whether emesis occurred, whether all or only part of the ingested foreign material was expelled during vomiting, whether the patient required further intervention to remove the ingested foreign material, and any immediate adverse effects observed following apomorphine administration (ie, while the dog was in the hospital).

Induction of emesis was considered successful if dogs retched and expelled stomach contents such as liquid, foam, or foreign material. Satisfactory or successful removal of foreign material from the stomach was defined as vomitus that contained foreign material of the type and amount ingested by the dog as described by the owner or radiographic evidence of the absence of foreign material in the stomach or presence of foreign material of a type, size, and volume that was deemed likely to safely pass through the remainder of the gastrointestinal tract. Patient outcome was determined by evaluation of medical records and telephone communications with owners. Information of interest included whether the dog developed any complications or required any additional interventions for gastric foreign body removal after it was discharged from the hospital for the study-qualifying visit.

Dogs that were treated for removal of a gastric foreign body multiple times during the study period were considered separate cases, and all cases that met the inclusion criteria were evaluated in the study. For analysis purposes, the type of foreign material ingested was classified into 11 categories as follows: balls, bathroom waste, fabric, foam material, hard material other than metal or rock, kitchen waste, leather, metal, rock, rope or string, and stuffed toys.

Apomorphine

The injectable formulation of apomorphine administered to the study dogs was prepared by a compounding pharmacy.a It was an aqueous compound with an apomorphine concentration of 3 mg/mL and was stable at room temperature (15° to 30°C [59° to 86°F]) for 6 months after the compounding date. The dose of apomorphine administered to each dog was determined by the attending clinician.

Statistical analysis

Data distributions were assessed for normality by use of the Shapiro-Wilk test and visual examination of normal probability plots. Results were reported as the mean ± SD or median (IQR) for continuous variables that were and were not normally distributed, respectively. The proportion of dogs for which the gastric foreign body was successfully removed by apomorphine-induced emesis (successful removal) was compared on the basis of age, sex, body weight, duration between ingestion and apomorphine administration, and foreign material category by means of χ2 or Wilcoxon rank sum tests. Successful removal was not compared on the basis of breed because there was too much variation within that variable. A Fisher exact test was used to compare successful removal between dogs that did (premedicated dogs) and did not receive drugs that might affect the efficacy of apomorphine (eg, opioids, sedatives, or antiemetics) before apomorphine administration. For each foreign material category, the proportion of dogs with successful removal was compared with that for all other categories combined by use of a χ2 test. All analyses were performed by use of a commercial statistical software program,b and values of P < 0.05 were considered significant.

Results

Dogs

Apomorphine was administered by the IV route to 1,704 dogs during the study period. Four hundred ninety-five dogs met the inclusion criteria and were evaluated in the study. Among the 1,209 dogs that were excluded from the study, 3 had incomplete records, 5 had small intestinal foreign bodies, 13 were determined to have not ingested any foreign material, and the remaining 1,188 were administered apomorphine subsequent to ingestion of a toxicant.

The 495 study dogs included 202 (41%) neutered males, 92 (19%) sexually intact males, 155 (31%) spayed females, and 46 (9%) sexually intact females. There were 74 (15%) mixed-breed dogs (including 12 Golden Retriever–Poodle mixes [goldendoodles]), and 433 (87%) purebred dogs representing 89 breeds. The most common breeds represented in the study were Labrador Retriever (n = 97 [20%]), Golden Retriever (37 [7%]), Boxer (17 [3%]), American Bulldog (15 [3%]), German Shepherd Dog (10 [2%]), and Shih Tzu (10 [2%]).

Apomorphine efficacy

The mean ± SD dose of apomorphine administered IV to the study dogs was 0.03 ± 0.01 mg/kg (0.014 ± 0.005 mg/lb). Apomorphine administration failed to induce emesis in 22 of 495 (4.4%) dogs but did induce emesis in 473 (95.6%; 95% CI, 93.7% to 97.4%) dogs. Among the 473 dogs that vomited, 457 (96.6%) did so after receiving only 1 dose of apomorphine. Apomorphine-induced emesis resulted in successful removal of the gastric foreign body for 374 of the 495 (75.6%; 95% CI, 71.8% to 79.4%) dogs. None of the dogs that had successful removal of the foreign body by apomorphine-induced emesis (successful removal) required further intervention for removal of foreign material from the gastrointestinal tract.

Twenty dogs were administered a second dose of apomorphine. The first dose of apomorphine administered was 0.03 mg/kg, 0.04 mg/kg (0.018 mg/lb), and 0.06 mg/kg (0.027 mg/lb) for 18, 1, and 1 dogs, respectively. The second dose ranged from 0.01 to 0.06 mg/kg, with 12 dogs receiving 0.03 mg/kg. Following administration of the second dose of apomorphine, 4 dogs failed to vomit and 5 dogs vomited, but the vomitus did not contain a satisfactory amount of foreign material. Successful removal was achieved in the remaining 11 dogs (55%; 95% CI, 21.1% to 68.9%).

The proportion of dogs with successful removal did not differ significantly (P = 0.10) by sex or neuter status. The median body weight of dogs with successful removal (19.7 kg [43.3 lb]; IQR, 9.8 to 31.0 kg [21.6 to 68.2 lb]) did not differ significantly (P = 0.24) from that for dogs without successful removal (22.5 kg [49.5 lb]; IQR, 10.0 to 36.8 kg [22.0 to 81.0 lb]). However, the median age of dogs with successful removal (1.54 years; IQR, 0.58 to 4.67 years) was significantly (P < 0.001) younger than that for dogs without successful removal (4.05 years; IQR, 1.31 to 6.83 years).

Fifteen of the 495 (3%) dogs were premedicated with drugs (eg, opioids, sedatives, or antiemetics) before apomorphine administration, and those drugs might have affected the efficacy of apomorphine in those dogs. Of the 15 dogs that received premedication, 6 were treated with a single medication including an opioid (n = 4), dexmedetomidine (1), and maropitant (1). The other 9 dogs received a combination of drugs (1 dog received acepromazine and an opioid, 2 dogs received midazolam and an opioid, and 6 dogs received dexmedetomidine and an opioid with 5 of these dogs also receiving atipamezole). Eleven of the 15 premedicated dogs did not vomit after apomorphine administration. Two premedicated dogs vomited after apomorphine administration, but the vomitus did not contain any foreign material. The remaining 2 premedicated dogs vomited with successful removal of the foreign body. The proportion of premedicated dogs that had successful removal (2/15 [13.3%]) was significantly (P < 0.001) less than the proportion of dogs that had successful removal without premedication (372/480 [77.5%]).

Information regarding the duration between ingestion of the foreign material and induction of emesis was available for 409 of the 495 (82.6%) dogs (Table 1). Successful removal was achieved in 316 (77.3%) of those dogs. The successful removal rate was highest for dogs in which emesis was induced within 2 hours after foreign material ingestion (174/204 [85.3%]). The successful removal rate progressively decreased as the duration between foreign material ingestion and emesis increased, with successful removal achieved in only 27 of 48 (56.3%) dogs in which emesis was induced > 24 hours after foreign material ingestion. The median duration between foreign material ingestion and emesis for dogs with successful removal (duration category, 1 [0 to 2 hours]; IQR, 1 [0 to 2 hours] to 2 [2 to 4 hours]) was significantly (P < 0.001) shorter than that for dogs in which successful removal was not achieved (duration category, 2 [2 to 4 hours]; IQR, 1 [0 to 2 hours] to 5 [12 to 24 hours]).

Table 1—

Frequency distribution of successful and unsuccessful removal of a gastric foreign body by apomorphine-induced emesis on the basis of duration between foreign material ingestion and emesis for 409 dogs.

Duration categoryNo. of dogsSuccessful removalUnsuccessful removal
1204174 (85.3)*30 (14.7)
211587 (75.7)28 (24.3)*
32618 (69.2)8 (30.8)
41610 (62.5)6 (37.5)
54827 (56.3)21 (43.7)

Values represent the number (%) of dogs unless otherwise indicated. The 409 dogs represent a subset of 495 dogs with a gastric foreign body that received apomorphine by the IV route. All dogs were examined and treated at a 24-hour emergency and referral veterinary hospital between January 1, 2010, and July 30, 2015. Duration categories 1, 2, 3, 4, and 5 correspond to 0 to 2, > 2 to 4, > 4 to 12, > 12 to 24, and > 24 hours between foreign material ingestion and apomorphine-induced emesis, respectively.

Represents the median duration category for the dogs represented in that column; the median duration category differed significantly (P < 0.001) between the 2 groups.

The types of foreign material ingested by the 374 dogs for which successful removal was achieved were summarized (Table 2). The respective proportions of dogs with successful removal following ingestion of leather objects (20/21 [95.2%]; P = 0.03), bathroom waste (39/41 [95.1%]); P < 0.01), and fabric (115/137 [83.9%]; P < 0.01) were significantly greater than the proportion of dogs with successful removal in the other 10 foreign material categories combined. Conversely, the respective proportions of dogs with successful removal following ingestion of metal objects (29/52 [55.8%]; P < 0.01), balls (6/13 [46.2%]; P = 0.01), and rocks (6/14 [42.9%]; P < 0.01) were significantly less than the proportion of dogs with successful removal in the other 10 foreign material categories combined.

Table 2—

Summary of material ingested by 495 dogs with a gastric foreign body that were included in a study to evaluate the efficacy of apomorphine-induced emesis for gastric foreign body removal.

Foreign material categoryDescriptionNo. of affected dogsNo. (%) of affected dogs within the category that were successfully treated by apomorphine-induced emesisP value*
BallsRubber36 (46.2)0.01
 Tennis4  
 Golf1  
 Foam3  
 Plastic2  
Bathroom wasteTampons2839 (95.1)< 0.01
 Sanitary napkins6  
 Condoms5  
 Diapers2  
FabricSock72115 (83.9)< 0.01
 Underwear21  
 Cloth31  
 Clothing6  
 Nylon7  
Foam materialSponge510 (76.9)0.91
 Bedding4  
 Cushion4  
Hard material other than metal or rockGlass223 (62.2)0.05
 Hard plastic31  
 Bone2  
 Shell1  
 Hard candy1  
Kitchen wasteCorn cob3175 (70.8)0.19
 Fruit pits12  
 Kabob skewers14  
 Bags14  
 Wrappers or packaging14  
 Cardboard or paper towel5  
 Rubber gloves2  
 Other14  
LeatherGloves820 (95.2)0.03
 Baseball cover4  
 Belt or band3  
 Boot4  
 Toys2  
MetalCoins929 (55.8)< 0.01
 Batteries3  
 Jewelry8  
 Steel wool5  
 Razor blades4  
 Fish hook1  
 Spoon1  
 Wire3  
 Pins or screws6  
 Other12  
RockRock146 (42.9)< 0.01
Rope or stringCollar or leash831 (86.1)0.13
 Gauze or bandage4  
 Hair ties9  
 Grass2  
 String or line9  
 Rope toys4  
Stuffed toysChildren's toy320 (80.0)0.60
 Dog toy22  

All dogs were examined and treated at a 24-hour emergency and referral veterinary hospital between January 1, 2010, and July 30, 2015. The dose of apomorphine administered to each dog was determined by the attending clinician. The mean ± SD dose of apomorphine administered to the study dogs was 0.03 ± 0.01 mg/kg (0.014 ± 0.005 mg/lb).

For χ2 test in which the successful removal rate for the given category was compared with the successful removal rate for all other categories combined; values of P < 0.05 were considered significant.

Seventy-two of the 121 (59.5%) dogs for which apomorphine-induced emesis failed to result in successful removal of the gastric foreign body underwent additional interventional procedures including endoscopy (n = 60) and exploratory laparotomy (12). The owners of the remaining 49 dogs with unsuccessful removal declined further intervention and instead monitored their pets at home. Follow-up information was obtained for 27 of those 49 (55%) dogs, and none required additional intervention.

Ninety-nine of the 495 (20%) study dogs received an antinausea medication or opioid antagonist after apomorphine administration. Medications administered included maropitant (n = 64), dolasetron (16), ondansetron (16), and naloxone (3). Those 99 dogs included dogs that did (n = 95) and did not (4) vomit. However, the records of only 4 of those dogs included documentation of adverse effects (signs of nausea [n = 2 dogs], tachycardia [1], and ataxia [1]) immediately after apomorphine administration that necessitated further medication.

Long-term follow-up information was obtained from the medical records or telephone communication with the owner for 390 of the 495 (78.8%) dogs. Two dogs for which apomorphine-induced emesis was unsuccessful and that subsequently underwent endoscopy for foreign body removal developed self-limiting emesis. Another dog was suspected of having aspiration pneumonia. That dog had radiographic evidence of aspiration prior to apomorphine administration, and the aspiration was believed to have most likely occurred when the owner orally administered vinegar to the dog in an attempt to induce emesis at home before bringing it to the hospital.

Discussion

To our knowledge, the present study was the first to evaluate the efficacy of IV administration of apomorphine to induce emesis in dogs with nontoxic gastric foreign bodies. Emesis was achieved in 473 of 495 (95.6%) dogs after administration of 1 (n = 457 dogs) or 2 doses (16) of apomorphine. Apomorphine-induced emesis resulted in successful removal of the gastric foreign body for 374 (75.6%) dogs (363 and 11 after administration of 1 and 2 doses of the drug, respectively). Successful removal of the foreign body by apomorphine-induced emesis was more likely to occur for dogs that were induced to vomit sooner rather than later after foreign material ingestion as well as for young dogs and dogs that ingested bathroom waste, fabric, or leather and less likely to occur for dogs that ingested balls, rocks, or metal objects. Adverse effects associated with apomorphine-induced emesis were rare.

The proportion of dogs that vomited following apomorphine administration in the present study (473/495 [95.6%]) was similar to that in another study5 in which dogs were administered apomorphine by either the conjunctival or IV route (59/63 [94%]). In that s t u d y,5 emesis was induced in all 26 dogs that received apomorphine by the IV route. In another study,10 492 of 596 (82.6%) dogs with a foreign body vomited following apomorphine administration by an ocular insert; however, information regarding whether apomorphine-induced emesis resulted in successful removal of the foreign body was not provided for those dogs. The authors of that study10 postulated that administration of apomorphine by means of ocular inserts might be less effective than IV administration for induction of emesis, especially in large dogs that require > 1 ocular insert to achieve therapeutic concentrations of the drug in the vomiting center. Administration of apomorphine as an IV bolus allows the drug to be more accurately dosed on the basis of patient body weight and more quickly achieves therapeutic drug concentrations at the vomiting center than does administration of apomorphine as an ocular insert, which relies on conjunctival absorption of the drug.

In the present study, dogs for which apomorphine-induced emesis resulted in successful removal of the foreign body were significantly younger than dogs with unsuccessful removal (ie, apomorphine failed to induce emesis or it did induce emesis, but the vomitus contained an unsatisfactory amount of the ingested foreign material). We believe this was a previously unreported finding. Young mammals have a high density of dopaminergic receptors in the brain, including in the vomiting center.11,12 That high density might enhance the sensitivity of young animals to apomorphine and thereby increase its effectiveness. Also, the blood-brain barrier is more permeable in young animals than in older animals,13 which may increase the influx of the drug into the vomiting center of the brain of young animals.

Twenty dogs of the present study received a second dose of apomorphine after the first dose failed to induce emesis. The second dose of apomorphine resulted in emesis in 16 of those dogs and successful removal of the foreign body in 11. Administration of a second dose of apomorphine to induce emesis in dogs has not been previously recommended.2,10 Apomorphine binds to dopamine receptors first, but once those receptors become saturated, additional apomorphine molecules bind to μ opioid receptors in the vomiting center of the brain, which depresses the vomiting response.4 The safety of administering 2 doses of apomorphine within a short period of time has been questioned because results of 1 study5 suggest there is a positive association between the incidence of adverse effects (particularly lethargy) and the number of doses of apomorphine administered. No adverse events were recorded for the 20 dogs that received 2 doses of apomorphine in the present study. Administration of the second dose of apomorphine increased the overall successful removal rate for the study population from 73.3% (363/495) to 75.6% (374/495). Had a second dose of apomorphine been administered to all 132 dogs with unsuccessful foreign body removal after the first dose, the overall successful removal rate likely would have increased, and this increase would have obviated the need for more invasive and expensive procedures such as endoscopy or laparotomy. The safety and efficacy of IV administration of 2 doses of apomorphine to induce emesis and gastric foreign body removal in dogs warrant further investigation.

In the present study, 11 of the 22 dogs that did not vomit had received medications prior to apomorphine administration. Drugs such as maropitant and acepromazine have direct centrally mediated anti-emetic effects. Maropitant is a neurokinin-1 receptor antagonist that blocks the pharmacological action of substance P in the vomiting center of the brain.12 Acepromazine directly affects dopamine D2 receptors in the chemoreceptor trigger zone.4,14,15 Opioids can also affect the efficacy of apomorphine because they may bind to μ opioid receptors in the vomiting center, which suppresses vomiting and prevents apomorphine from binding to those receptors.4,16 The emetic effects of apomorphine are also centrally mediated, so any drug that directly affects the vomiting center of the brain is likely to affect the efficacy of apomorphine.

Results of the present study indicated that removal of a gastric foreign body by apomorphine-induced emesis was more likely to be successful when emesis was induced as soon as possible after ingestion of the foreign material. Prolonged exposure of the gastric mucosa to foreign material may result in progressive inflammation and edema, which may impair gastric motility. Edema can also impinge on the lumen of the cardiac sphincter, thereby impairing ejection of the foreign material when emesis is induced. Over time, foreign material may collect in the antrum of the stomach owing to migrating motor complex activity, which facilitates removal of indigestible particles from the stomach.17 Pressure on the foreign material from continuous migrating motor complex activity may result in the material becoming lodged in the antrum or pylorus so that it cannot be expelled during emesis.

For the dogs of the present study, the efficacy of apomorphine-induced emesis for gastric foreign body removal varied on the basis of the type of foreign material ingested. The most common foreign materials ingested by the dogs of this study were fabric, kitchen waste, and metal objects. However, the successful removal rate was greatest for dogs that ingested leather (20/21 [95.2%]) and bathroom waste (39/41 [95.1%]), which was likely attributable to the fact that the duration between ingestion and emesis for those dogs was often < 2 hours. Dogs that ingest leather and bathroom waste often leave evidence for their owners to find, which may translate into quicker veterinary intervention. Conversely, dogs can quickly and easily ingest rocks and metal objects without leaving any evidence behind, and dogs with such foreign bodies may not be identified until hours to days later when they develop clinical signs, such as vomiting, inappetence, or signs of nausea, and are examined by a veterinarian. Interestingly, for dogs that ingested balls, the median duration between ingestion and apomorphine-induced emesis was ≤ 2 hours, but the successful removal rate was only 46.2% (6/13). Unfortunately, the size, shape, and weight of the ingested foreign bodies were generally not recorded in the medical records, so it was not possible to identify factors associated with the fairly low successful removal rates for balls, rocks (6/14 [42.9%]), and metal objects (29/52 [55.8%]).

Seventy-two dogs of the present study underwent either endoscopy (n = 60) or exploratory laparotomy (12) after IV administration of apomorphine failed to result in successful removal of the gastric foreign body. Endoscopic and surgical interventions for foreign body removal are more expensive and are associated with an increased risk for morbidity and death, compared with drug-induced emesis. In 1 study,18 dogs that underwent surgical intervention for removal of linear and nonlinear gastrointestinal foreign bodies were hospitalized for 3 and 2 days, respectively. Mortality rates for dogs that undergo surgery (gastrotomy, enterotomy, and intestinal resection-anastomosis) for foreign body removal range from 1% to 6%.8,9,18 Most dogs of the present study were successfully treated on an outpatient basis with no or only minor adverse effects, which suggested that apomorphine-induced emesis was a safe and effective treatment option for dogs with gastric foreign bodies.

Minor adverse effects (signs of nausea [n = 2], tachycardia [1], and ataxia [1]) that developed immediately after apomorphine administration were recorded for only 4 of the 495 (0.8%) dogs of the present study. However, 99 (20%) dogs received antinausea medications after apomorphine administration, most likely as a prophylactic measure against further emesis or signs of nausea because none of those dogs were described as having intractable vomiting or sustained signs of nausea. Two dogs were reported to have self-limiting emesis after hospital discharge. Both of those dogs underwent endoscopy, and the emesis might have been a consequence of gastritis associated with the endoscopic procedure or gastric mucosal irritation caused by the foreign body. Compared with administration of apomorphine by means of an ocular insert, the adverse effects associated with IV administration of apomorphine are narrower in scope but the incidence of immediate adverse effects (eg, tachycardia and sedation) is higher.10 In the present study, following apomorphine administration, only one dog became tachycardic and another dog became ataxic, most likely from apomorphine-induced CNS depression.2,10

Anecdotal reports suggest that dogs occasionally reingest vomited foreign material, so careful supervision during induced emesis is advised. The dogs of the present study were closely monitored until emesis was complete, and none of the dogs reingested expelled foreign material.

The present study had some limitations. Owing to its retrospective nature, the dose of apomorphine was not standardized. The initial dose of apomorphine administered was most commonly 0.03 mg/kg. Only 20 dogs received a second dose of apomorphine, which was quite variable (0.01 to 0.06 mg/kg). Although follow-up information was obtained for most dogs, some patients that required additional interventions may have gone unidentified. It is often recommended that animals be fed a small amount of food before emesis is induced.5 Information regarding feeding was not recorded in the medical records, so the association between feeding and the efficacy of apomorphine-induced emesis could not be evaluated. The medical record search criteria included only dogs that received an injectable apomorphine formulation; it did not include gastric foreign body. Thus, dogs with gastric foreign bodies that were not treated with apomorphine were excluded from the study. Induction of emesis is not recommended for removal of some foreign bodies, such as razor blades, needles, or other sharp objects. Consequently, we cannot comment on the efficacy of apomorphine-induced emesis for removal of all types of gastric foreign bodies in dogs. It is also possible that the history, particularly the medication administration history, recorded in the medical record was incomplete for some dogs, and some dogs might have received apomorphine or other emetics prior to being referred to the study hospital for treatment.

Results of the present study indicated that IV administration of apomorphine was safe and effective for induction of emesis in dogs and that apomorphine-induced emesis was a viable alternative for removal of gastric foreign bodies, particularly if the ingested foreign material consisted of fabric, leather, or bathroom waste. If successful removal of the foreign body is not achieved after 1 dose of apomorphine, administration of a second dose should be considered. The likelihood of successful foreign body removal by apomorphine-induced emesis decreased as the duration between foreign material ingestion and emesis increased. Additionally, some medications, such as opioids, sedatives, and antiemetics, can impair the efficacy of apomorphine. Therefore, dogs should be examined as soon as possible after foreign body ingestion and should not be treated with any medications that might affect the activity of emetics such as apomorphine.

Acknowledgments

No third-party funding or support was received in connection with this study or the writing or publication of the manuscript. The authors declare that there were no conflicts of interest.

The authors thank Rachel Conklin and Kristina Males for assistance with data acquisition and Dr. Joe Hauptman for assistance with statistical analyses.

ABBREVIATIONS

CI

Confidence interval

IQR

Interquartile (25th to 75th percentile) range

Footnotes

a.

Wedgewood Pharmacy, Swedesboro, NJ.

b.

SAS, version 9.3, SAS Institute Inc, Cary, NC.

References

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