Dolasetron
Dolasetron is a potent **5-HT3 receptor antagonist** utilized primarily as an antiemetic in veterinary medicine. It is particularly effective for managing severe nausea and vomiting associated with cancer chemotherapy in dogs and cats. * **Dosing Convenience**: Unlike ondansetron, which often requires multiple daily doses, dolasetron can typically be administered **once daily**. * **Formulation Challenges**: While the injectable form is highly practical for in-hospital use, the commercially available human oral tablets (50 mg and 100 mg) are too large for direct administration to most small animals. Consequently, oral use usually requires compounding. > **Clinical Pearl**: Due to cost and formulation constraints, other antiemetics like maropitant (Cerenia) or ondansetron are often preferred for routine outpatient use, reserving dolasetron for refractory cases or specific chemotherapy protocols.
Mechanism: Dolasetron exerts its anti-nausea and antiemetic effects by selectively antagonizing **5-hydroxytryptamine 3 (5-HT3) receptors**. * **Peripheral Pathway**: Chemotherapy and severe GI insults cause the release of serotonin from mucosal enterochromaffin cells in the small intestine. Serotonin binds to 5-HT3 receptors on **vagal afferent nerve terminals**, sending emetogenic signals to the brain. Dolasetron blocks this interaction. * **Central Pathway**: Dolasetron also blocks 5-HT3 receptors located directly within the **Chemoreceptor Trigger Zone (CRTZ)** in the central nervous system. Once administered, dolasetron is rapidly converted by carbonyl reductase into its active metabolite, **hydrodolasetron**, which is primarily responsible for the pharmacological effects.
Dosing by species
- Anti-emetic, particularly for patients receiving chemotherapeutics ยท 0.6 mg/kg IV once daily ยท IV ยท q24h
- Vomiting disorders ยท 0.6-1 mg/kg PO q12h ยท PO ยท q12h
- Prevent vomiting ยท 0.6 mg/kg IV or PO once daily ยท IV/PO ยท q24h
- Treat vomiting ยท 1 mg/kg PO or IV once daily ยท PO/IV ยท q24h
- General anti-emetic ยท 0.6 mg/kg IV q12h or 0.6-1 mg/kg PO q12h ยท IV/PO ยท q12h
- Anti-emetic, particularly for patients receiving chemotherapeutics ยท 0.6 mg/kg IV once daily ยท IV ยท q24h
- General anti-emetic ยท 0.6 mg/kg IV q24h or 0.5 mg/kg PO, SC or IV q24h ยท IV/PO/SC ยท q24h
- Vomiting disorders ยท 0.6-1 mg/kg PO q12h ยท PO ยท q12h
- Prevent vomiting ยท 0.6 mg/kg IV or PO once daily ยท IV/PO ยท q24h
- Treat vomiting ยท 1 mg/kg PO or IV once daily ยท PO/IV ยท q24h
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Known hypersensitivity to dolasetron
- Atrioventricular (AV) block II to III
- Markedly prolonged QTc interval
Adverse effects
- Dose-related ECG interval prolongation (PR, QTc, JT prolongation, and QRS widening)
- Headache (reported in humans)
- Dizziness (reported in humans)
Drug interactions
- Atenolol ยท May reduce the clearance and increase blood levels of hydrodolasetron
- Cimetidine ยท May reduce the clearance and increase blood levels of hydrodolasetron
- Ketoconazole ยท May reduce the clearance and increase blood levels of hydrodolasetron
- Phenobarbital ยท Can reduce hydrodolasetron blood levels
- Rifampin ยท Can reduce hydrodolasetron blood levels
Monitoring
- Efficacy (resolution of nausea and vomiting)
- Heart rhythm (ECG) in at-risk patients (e.g., those with electrolyte imbalances or on arrhythmogenic drugs)
Overdose
Data on overdosage is very limited. * **Clinical Signs**: In humans, a massive overdose (13 mg/kg) resulted in severe hypotension and dizziness. * **Treatment**: Manage overdoses with supportive therapy, including IV fluids and pressors if hypotension occurs. * **Toxicity**: Lethal intravenous doses in mice and rats were 160 mg/kg and 140 mg/kg, respectively.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.