Objective—To evaluate the effect of erythromycin on
motility of the ileum, cecum, and pelvic flexure of horses
during the postoperative and post-recovery periods.
Animals—8 healthy adult horses.
Procedure—Horses were anesthetized and bipolar
electrodes were implanted in smooth muscle of the
ileum, cecum, and pelvic flexure. Approximately 4, 16,
and 24 hours (postoperative recording sessions) and
at least 8 days (post-recovery recording session) after
surgery, myoelectric activity was recorded before and
after administration of erythromycin (0.5 mg/kg).
Results—Following erythromycin administration,
myoelectric activity was increased in the ileum during
all postoperative recording sessions but not during
the post-recovery recording session. Myoelectric
activity was increased in the cecum following erythromycin
administration only during the post-recovery
recording session. Myoelectric activity was
increased in the pelvic flexure following erythromycin
administration during all recording sessions. During
several recording sessions, there were short periods
during which myoelectric activity was significantly
decreased following erythromycin administration.
Conclusions and Clinical Relevance—Results suggest
that erythromycin has an effect on myoelectric
activity of the ileum, cecum, and pelvic flexure in
horses; however, prokinetic effects of erythromycin
administered during the postoperative period were
not always the same as effects obtained when the
drug was administered after horses had recovered
from the effects of surgical implantation of recording
devices. Therefore, caution must be exercised when
extrapolating results of prokinetic studies in healthy
animals to animals with abnormal gastrointestinal
tract motility. (Am J Vet Res 2000;61:420–424)
Objective—To evaluate effects of IV administration of
penicillin G potassium (KPEN) or potassium chloride
(KCl) on defecation and myoelectric activity of the
cecum and pelvic flexure of horses.
Animals—5 healthy horses.
Procedure—Horses with 12 bipolar electrodes on the
cecum and pelvic flexure received KPEN or KCl solution
by IV bolus 4 hours apart. Each horse received
the following: 2 × 107 U of KPEN (high-dose KPEN) followed
by 34 mEq of KCl (high-dose KCl), 1 × 107 U of
KPEN (low-dose KPEN) followed by 17 mEq of KCl
(low-dose KCl), high-dose KCl followed by high-dose
KPEN, and low-dose KCl followed by low-dose KPEN.
Number of defecations and myoelectric activity were
recorded for 60 minutes. The first three 5-minute segments
and first four 15-minute segments of myoelectric
activity were analyzed.
Results—Number of defecations during the first 15-
minute segment was greater after high-dose KPEN
treatment than after high-dose or low-dose KCl treatment.
Compared with reference indexes, myoelectric
activity was greater in the pelvic flexure for the first 5-
minute segment after high-dose KCl treatment, in the
cecum and pelvic flexure for the first 5-minute segment
and in the pelvic flexure for the first 15-minute
segment after low-dose KPEN treatment, and in the
pelvic flexure for the first and second 5-minute segments
and the first three 15-minute segments after
high-dose KPEN treatment.
Conclusions and Clinical Relevance—IV administration
of KPEN stimulates defecation and myoelectric
activity of the cecum and pelvic flexure in horses.
Effects of KPEN may be beneficial during episodes of
ileus. (Am J Vet Res 2003;64:1360–1363)