Alprazolam
**Alprazolam** is a potent, short-to-intermediate-acting **benzodiazepine** primarily used in veterinary medicine as an anxiolytic and mild sedative. It is a Schedule IV (C-IV) controlled substance. Key clinical highlights include: - **Behavioral Modification**: Frequently prescribed as an adjunctive therapy for panic disorders, storm phobias, separation anxiety, and inappropriate elimination (e.g., feline urine marking). - **Motor Function**: Compared to diazepam, alprazolam may have less negative impact on motor function at lower doses, making it favorable for ambulatory patients. - **Clinical Pearl**: Because it is highly lipid-soluble, it has a rapid onset when given orally, making it ideal for situational anxieties (e.g., thunderstorms, fireworks) if administered 30-60 minutes prior to the trigger event.
Mechanism: Alprazolam exerts its effects by binding to specific **benzodiazepine receptors** located on the **GABA-A receptor complex** in the central nervous system. - **Mechanism**: Binding โ enhances the affinity of the receptor for **gamma-aminobutyric acid (GABA)** โ increases the frequency of chloride channel opening โ cellular hyperpolarization โ decreased neuronal excitability. - **Target Areas**: It primarily depresses subcortical levels of the CNS, specifically the **limbic system**, **thalamus**, and **hypothalamus**. - **Net Effect**: This enhanced inhibitory neurotransmission produces the characteristic anxiolytic, sedative, skeletal muscle relaxant, and anticonvulsant effects.
Dosing by species
- For treatment of canine anxiety disorders ยท 0.01-0.1 mg/kg PO as needed for panic, not to exceed 4 mg/dog/day. Start with 1-2 mg (total dose) for a medium-sized dog. ยท PO ยท prn
- For separation anxiety ยท 0.25 mg-2 mg (total dose) once daily to three times daily PO. ยท PO ยท q8-24h
- For storm phobias ยท 0.02-0.4 mg/kg PO q4h as needed ยท PO ยท q4h ยท Helps to minimize impact of experiencing a severe storm
- For storm phobias (adjunct) ยท 0.02 mg/kg PO as needed one hour before anticipated storm and every 4 hours as needed ยท PO ยท q4h ยท Used as an adjunct after behavior modification and prior clomipramine treatment
- For phobias, night waking ยท 0.01-0.1 mg/kg or 0.25-2 mg (total dose) per dog PO q6-12h PO ยท PO ยท q6-12h
- For acute anxiety ยท 0.05-0.1 mg/kg PO prn or three times a day. Administer 30-60 minutes prior to trigger event. ยท PO ยท prn or q8h
- Anxiolysis and fear-related disorders ยท 0.01-0.1 mg/kg ยท PO ยท prn up to q6h ยท As needed ยท Titrate up or down to the minimum effective dose. Best given ~30 mins before a fear-inducing event.
- For treatment of feline anxiety disorders ยท 0.125-0.25 mg/kg PO q12h (Start at 0.125 mg/kg PO) ยท PO ยท q12h
- For refractory house soiling ยท 0.1 mg/kg or 0.125-0.25 mg (total dose) per cat PO q8-12h ยท PO ยท q8-12h
Routes of administration
Contraindications
- Known benzodiazepine hypersensitivity
- Aggressive animals (controversial; anxiety reduction may disinhibit aggressive tendencies)
Adverse effects
- Sedation
- Increased appetite (polyphagia)
- Transient ataxia
- Behavior changes in cats (irritability, increased affection, depression, aberrant demeanor)
- Paradoxical CNS excitement/agitation (rare in dogs)
- Physical dependence (with chronic use)
- Impeded learning and retarded training
Drug interactions
- Antacids ยท May slow the rate, but not the extent of oral absorption of alprazolam; administer 2 hours apart.
- CNS Depressant Agents (barbiturates, narcotics, anesthetics) ยท Additive CNS depression effects may occur.
- Digoxin ยท Serum levels of digoxin may be increased; monitor for toxicity.
- Fluoxetine, Fluvoxamine ยท Increased alprazolam levels.
- Hepatically Metabolized Drugs (Cimetidine, erythromycin, isoniazid, ketoconazole, itraconazole) ยท Metabolism of alprazolam may be decreased, leading to excessive sedation.
- Rifampin ยท May induce hepatic microsomal enzymes and decrease the pharmacologic effects of benzodiazepines.
- Tricyclic Antidepressants (Amitriptyline, Clomipramine, Imipramine) ยท Alprazolam may increase levels of these drugs; concurrent use with clomipramine may improve efficacy for phobias.
- Itraconazole ยท Inhibits alprazolam metabolism, potentially increasing sedation and toxicity ยท major
- Ketoconazole ยท Inhibits alprazolam metabolism ยท major
- Clomipramine ยท Used concurrently as an adjunct, but may have additive CNS depressant effects ยท minor
Monitoring
- Clinical efficacy (reduction in anxiety/panic)
- Adverse effects (excessive sedation, paradoxical excitation)
- Hepatic enzymes (particularly when treating cats chronically)
Overdose
Overdoses are generally limited to **CNS signs**, primarily dose-dependent CNS depression. - **Clinical Signs**: Ataxia, lethargy, disorientation, and vomiting. Some animals may present with a **paradoxical reaction** (hyperactivity, vocalization, agitation) which may be followed by CNS depression. Severe signs like hypotension, respiratory depression, and cardiac arrest are quite rare in small animals. - **Toxicity**: The reported LD50 in rats is >330 mg/kg, but cardiac arrest has occurred at doses as low as 195 mg/kg. - **Treatment**: Consists of standard protocols for decontamination. The decision to give activated charcoal should be weighed carefully against the risk of aspiration if the patient is sedated. **Flumazenil** can be used to reverse the sedative effects, but is generally reserved for cases with significant CNS and respiratory depression.
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.