Buspirone
Buspirone is an azapirone-class, non-benzodiazepine anxiolytic agent used primarily in veterinary medicine for the management of generalized anxiety, mild phobias, and feline urine marking/spraying. Unlike benzodiazepines, buspirone lacks sedative, muscle relaxant, and anticonvulsant properties, making it ideal for long-term behavioral management without causing significant cognitive or psychomotor impairment. **Clinical Pearls:** * **Delayed Onset:** It requires chronic administration (typically 1 to 4 weeks) to alter receptor density and achieve full clinical efficacy. * **Not for Acute Panic:** Because of its delayed onset, it is inappropriate and ineffective as a sole therapy for acute, situational panic (e.g., immediate thunderstorm response or acute separation anxiety events). * **Social Dynamics:** It is particularly useful for anxieties associated with social interactions and may be more effective in multi-cat households than in single-cat households.
Mechanism: Buspirone is an anxioselective agent that acts primarily as a partial agonist at **serotonin (5-HT1A) receptors** and as an agonist/antagonist at presynaptic **dopamine (D2) receptors** in the CNS. * **Serotonin Pathway:** By binding to 5-HT1A autoreceptors โ it slows the neuronal firing rate โ decreasing the depletion of serotonin stores and modulating serotonergic tone over time. * **Receptor Specificity:** It does **not** share mechanisms with benzodiazepines; it has no significant affinity for benzodiazepine receptors and does not affect GABA binding.
Dosing by species
- Adjunctive treatment of low-grade anxieties/fears, spraying, overgrooming ยท 0.5-1 mg/kg PO q8-12h; 2.5-5 mg (total dose) per cat PO q8-12h ยท PO ยท q8-12h ยท 6-8 weeks ยท some cats do well on once daily dosing
- Adjunctive treatment of low-grade anxieties/fears, spraying, overgrooming ยท 2.5-5 mg (total dose) PO once a day to 3 times a day ยท PO ยท q8-24h
- Urine marking ยท 2.5-7.5 mg (total dose) per cat PO q12h ยท PO ยท q12h
- Adjunctive treatment of low-grade anxieties/fears, spraying, overgrooming ยท 0.5-1 mg/kg PO q12h; 2.5-7.5 mg (total dose) per cat PO q12h ยท PO ยท q12h
- Social phobias, panic disorders ยท 0.5-1 mg/kg PO q8-12h ยท PO ยท q8-12h ยท most useful in social phobias; may also be useful for panic disorders
- Low-grade anxieties and fears ยท 1 mg/kg PO q8-24h (mild anxiety); 2.5-10 mg (total dose) per dog PO q8-24h (mild anxiety); 10-15 mg per dog PO q8-12h (more severe anxiety, thunderstorm phobia) ยท PO ยท q8-24h or q8-12h
- Low-grade anxieties and fears ยท 1-2 mg/kg PO q12h; 5-15 mg (total dose) per dog PO q8-12h ยท PO ยท q8-12h or q12h
- Low-grade anxieties and fears ยท 5-10 mg (total dose) PO q8-12h ยท PO ยท q8-12h
- Global anxiety ยท 0.5-2 mg/kg PO q8-12h ยท PO ยท q8-12h ยท may take 2-4 weeks until effect
Routes of administration
Contraindications
- Severe hepatic disease (use with caution)
- Severe renal disease (use with caution)
- Aggressive animals (may reduce disinhibition)
- Working dogs (use with caution despite low sedation)
- Acute situational anxieties (as sole therapy)
Adverse effects
- Bradycardia
- Gastrointestinal disturbances
- Stereotypic behaviors
- Increased affection (cats)
- Paradoxical aggression/turning on attackers (previously timid cats)
- Dizziness (humans)
- Headache (humans)
- Nausea/anorexia (humans)
- Restlessness (humans)
- Tachycardia (rare)
Drug interactions
- Tricyclic or SSRI agents ยท May be used in combination, but dosage reductions may be necessary to minimize adverse effects
- CNS Depressants ยท Potentially could cause increased CNS depression
- Diltiazem ยท May cause increased buspirone plasma levels and adverse effects
- Erythromycin ยท May cause increased buspirone plasma levels and adverse effects
- Grapefruit juice (powder) ยท May cause increased buspirone plasma levels and adverse effects
- Ketoconazole, Itraconazole ยท May cause increased buspirone plasma levels and adverse effects
- Monoamine Oxidase Inhibitors (e.g., selegiline, amitraz) ยท Use with buspirone is not recommended because dangerous hypertension may occur
- Rifampin ยท May cause decreased buspirone plasma levels
- Trazodone ยท Use with buspirone may cause increased ALT
- Verapamil ยท May cause increased buspirone plasma levels
Monitoring
- Efficacy (reduction in anxiety, spraying, or fear behaviors)
- Adverse effect profiles (GI upset, behavioral changes)
Overdose
Limited information is available in veterinary species. The oral LD50 in dogs is 586 mg/kg. **Clinical Signs of Overdose:** * Vomiting * Dizziness * Drowsiness * Miosis (constricted pupils) * Gastric distention **Treatment:** Standard overdose protocols (e.g., decontamination, supportive care) should be followed after ingestion has been determined.
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.