Alfaxalone Use in Dogs and Cats
Introduction Alfaxalone is a neuroactive steroid anesthetic used in veterinary medicine for sedation and general anesthesia in dogs and cats. It is known for its rapid onset, short duration of action, and minimal cardiovascular effects, making it a preferred choice in various clinical settings.
Pharmacology Alfaxalone is a synthetic neurosteroid that acts as a positive allosteric modulator of gamma-aminobutyric acid (GABA) receptors. By enhancing GABAergic inhibitory neurotransmission, alfaxalone induces a dose-dependent depression of the central nervous system, leading to sedation, hypnosis, and anesthesia. It is rapidly metabolized in the liver and excreted primarily via the biliary system and urine.
Indications Alfaxalone is primarily used for:
- Induction of anesthesia before maintenance with inhalant anesthetics
- Total intravenous anesthesia (TIVA) protocols
- Sedation for minor procedures and diagnostic imaging
- Anesthetic induction in high-risk patients, including those with cardiovascular disease
Dosage and Administration Alfaxalone is typically administered intravenously (IV) but can also be given intramuscularly (IM) for sedation. The recommended dosages are:
- IV Induction in dogs: 1-3 mg/kg bolus over 60 seconds
- IV Induction in cats: 2-5 mg/kg bolus over 60 seconds
- IM Sedation in dogs: 0.5-2 mg/kg
- IM Sedation in cats: 2-5 mg/kg Dosages may vary based on patient factors, including age, health status, and concurrent medications.
Effects and Benefits
- Rapid onset (30-60 seconds IV, 5-15 minutes IM)
- Short duration (5-10 minutes after IV administration)
- Smooth and predictable recovery
- Minimal cardiovascular depression
- Suitable for high-risk and critically ill patients
Adverse Effects
- Dose-dependent respiratory depression
- Hypotension at high doses
- Excitation or twitching during induction or recovery
- Possible pain on injection (especially IM)
- Transient apnea, particularly with rapid IV administration
Contraindications and Precautions
- Hypersensitivity to alfaxalone
- Severe hepatic dysfunction
- Use with caution in patients with respiratory compromise
- Avoid in cases of untreated hypovolemia or shock
- Careful monitoring required for repeated doses due to cumulative effects
Use in Combination with Other Anesthetic Agents Alfaxalone is often used in combination with:
- Pre-medications: Opioids (e.g., methadone, fentanyl), benzodiazepines (e.g., midazolam), or alpha-2 agonists (e.g., dexmedetomidine)
- Maintenance anesthesia: Inhalants (e.g., isoflurane, sevoflurane) or continuous rate infusion (CRI) of alfaxalone
- Adjuncts for analgesia: NSAIDs, local anesthetics, and ketamine
Regulatory and Handling Considerations Alfaxalone is a Schedule IV controlled substance in some jurisdictions, requiring appropriate handling, storage, and documentation. It should be stored at room temperature and used within the recommended time after vial opening (usually 28 days if preserved, single-use otherwise).
Conclusion Alfaxalone is a valuable anesthetic agent for dogs and cats, offering reliable sedation and anesthesia with a favorable safety profile. Proper dosing, monitoring, and supportive care are essential to maximize benefits and minimize risks associated with its use.
