Page 607 - Clinical Small Animal Internal Medicine

53 Motility Disorders of the Alimentary Tract 575

Table 53.2 Mechanism and site of action, dosages and important clinical information for drugs with prokinetic actions in small animals
VetBooks.ir Class Site of action Dose Other properties Comments

Serotonergic 5‐HT 4 agonists
Cisapride GES, stomach, 0.1–0.5 mg/ 5‐HT 3 antagonist Removed from the human
intestine, colon, kg PO TID‐BID 5‐HT 2 antagonist market due to severe cardiac
CRTZ 5‐HT 1 agonist arrhythmias; in some canine
studies no effect on gastric
emptying; in high doses (3 mg/
kg) decreases gastric motility
Mosapride Stomach, colon 0.25–2 mg/kg PO BID; None
5 mg/cat BID
Prucalopride Stomach, small and Dog: 0.01–0.16 mg/kg SID None Can be administered rectally as
large intestine stimulates gastric well if oral administration is
emptying not considered safe (risk of
0.6 mg/kg SID stimulates aspiration) or gastric motility
GI peristalsis is severely impaired
1–1.25 mg/kg SID induces
migrating motor
complexes (defecation)
Dosages up to 2 mg/kg
SID described

Cat: 0.24–0.5 mg/kg SID
Tegaserod Small and large 0.05–0.1 mg/kg PO or IV 5‐HT 1 antagonist Not currently on the market
intestine BID (allegedly increased risk of
cardiovascular disease in
people)
Motilin‐like substances
Erythromycin GES, stomach, small 0.5–1 mg/kg PO or IV 5‐HT 1 antagonist Induces interdigestive motility,
and large intestine BID which might lead to “dumping”
of gastric contents into the
duodenum before appropriate
digestion can take place
Acetylcholinesterase inhibitors
Ranitidine Stomach, colon 1–2 mg/kg PO BID‐TID H2‐histaminergic Probably only mild to no
or slow IV/CRI antagonist prokinetic effects
Nizatidine Stomach, colon 1 mg/kg IV BID; 2.5 mg/ H2‐histaminergic Probably even less effective
kg PO SID–BID antagonist than ranitidine
Others/Miscellaneous
Bethanechol Esophagus 5–15 mg/dog PO TID Cholinomimetic
substance
Mirtazapine Stomach, others 0.6 mg/kg PO SID Noradrenergic and Limited clinical data available,
unknown In experimental dogs: specific serotonergic but at 2 mg/kg SID showed
2 mg/kg SID tricyclic antidepressant accelerated gastric emptying
times in experimental
fistulated dogs
Source: Modified from Washabau and Day (2013). Reproduced with permission of Elsevier.
BID, twice a day (bis in die); CRI, continuous rate infusion; CRTZ, chemoreceptor trigger zone; GES, gastroesophageal sphincter;
GI, gastrointestinal; IV, intravenous; PO, by mouth (per os); SID, once a day (semel in die); TID, three times a day (ter in die).

by increased defecation frequency, decreased fecal vol- defecation (tenesmus). In its most severe form, constipa-
ume per defecation, tenesmus, increased fecal mucus, tion leads to obstipation where impacted, hard and dry
and the occurrence of fresh blood (hematochezia). feces make normal defecation impossible. Typically own-
Large intestinal hypomotility results in constipation, ers observe frequent attempts to defecate, tenesmus and
which is defined as absent, infrequent or difficult dyschezia (difficult or painful defecation) with little or