Table 10.
Antiemetic drugs in dogs
| Drug group and drug doses | Receptor pharmacology | Pathways inhibited | Other actions (including adverse effects) | Side‐effects and contraindications | Reference (LOE) | Overall evidence grade (anti‐emetic action) |
|---|---|---|---|---|---|---|
| Phenothiazines | D2 and H1 receptor antagonist. Anticholinergic and anti‐serotinergic actions (weaker) | Central emetogens (anti‐D2); motion sickness (anti‐H1) | Alpha1 receptor antagonist | Pre‐licensing safety studies not performed. | 201 (3b) | B |
| Acepromazine: 0.01‐0‐05 mg/kg i.m., s.c. 1‐3 mg/kg p.o. | Decreases blood pressure in dehydrated animals | 202 (2c) | ||||
| Chlorpromazine: 0.5 mg/kg i.m., s.c. q6‐8h | Anti‐cholinergic side effects | 203 (1b) | ||||
| Movement disorders | ||||||
| Sedative actions | ||||||
| Butyrophenones | D2 antagonist | Central emetogenic pathway | Alpha1 receptor antagonists | Pre‐licensing safety studies not performed. | 117 (2b) | C |
| Domperidone: 2‐5 mg per animal q8h | Decreases blood pressure in dehydrated animals | 112 (2b) | ||||
| Sedative actions | ||||||
| Metoclopramide: 0.2‐05 mg/kg i.m., s.c., p.o. q6‐8h or 1‐2 mg/kg i.v. over 24 hours as slow constant rate infusion. | D2 antagonist 5‐HT3 antagonist (weak) H1 antagonist (weak) | Central emetogenic pathway (D2 antagonism); some action versus peripheral emetogens | Variable prokinetic effect (peripheral) which may contribute to antiemetic action in some, but not all cases | Pre‐licensing safety studies not performed. | 204 (2b) | B |
| Some effect vs. motion sickness (weak) | Increases detrusor muscle contractility reducing bladder capacity | 205 (1b) | ||||
| At high doses reduces gastro‐oesophageal reflux associated with anaesthesia and dopamine‐induced inhibition of lower oesophageal sphincter tone | Movement disorders Extrapyramidal signs | 206 (1b) | ||||
| 207 (3b) | ||||||
| 117 (2b) | ||||||
| 208 (1b) | ||||||
| 209 (1b) | ||||||
| 210 (2b) | ||||||
| 114 (1b) | ||||||
| 211 (2b) | ||||||
| 212 (2b) | ||||||
| Ondansetron: 0.5 mg/kg i.v. loading dose followed by 0.5 mg/kg/h infusion for 6 hours or 0.5‐1 mg/kg p.o. q12‐24 hours | 5‐HT3 selective antgonists | Works best versus acute peripheral emetogens (e.g. chemical irritants to the gut ‐ cisplatin causing degranulation of enterochromaffin cells and 5‐HT release). Also effective vs. radiation induced emesis. | 5‐HT3 receptors are involved in regulating GI motility so blockade could disrupt these physiological functions | Pre‐licensing safety studies not performed. | 213 (2b) | B |
| Represented a major breakthrough in preventing acute (but not delayed) emesis associated with cancer chemotherapy. | 5‐HT3 receptors involved in sleep‐induced apnoea; ondansetron inhibits this phenomenon | Dose escalation studies in for human toxicity suggests safe at 100 times normal dose | 214 (2b) | |||
| Relatively ineffective versus central emetic stimuli | 215 (2b) | |||||
| 216 (1b) | ||||||
| 217 (1b) | ||||||
| 218 (2b) | ||||||
| 114 (1b) | ||||||
| 219 (2b) | ||||||
| 220 (3b) | ||||||
| 221 (1b) | ||||||
| 222 (2b) | ||||||
| Maropitant: standard emesis 1mg/kg s.c. q24h. For prevention of motion sickness up to 8mg/kg p.o. q24h for maximum of 2 days | NK1 receptor antagonists (highly selective) | Work well versus both peripheral and central emetogens. | Binds to voltage dependent calcium channels at very high concentrations; significant inhibition only seen at concentrations 77 times peak plasma concentrations when dosed at 8mg/kg (bradycardia, decrease in BP) | Use with caution in cardiac disease, hepatic disease, hypoproteinaemia and when administering other highly protein bound drugs. * | 128 (1b) | A |
| Higher dose required to prevent motion sickness | 129 (1b) | |||||
| Anti‐nausea effect more difficult to measure and assess clinically | 206 (1b) | |||||
| 119 (1b) | ||||||
| 114 (1b) | ||||||
| 223 (1b) | ||||||
| 224 (2b) |
*Safety of maropitant in lactating/pregnant bitches and in dogs <16 weeks old is not established. US Food and Drug Administration licence contraindicates use in these groups and where GI obstruction or toxin ingestion suspected. European Medicines Agency (EMEA) Summary of Product Characteristics advises risk/benefit assessment by veterinarian in these situations.