Oxazepam
Oxazepam is a short-to-intermediate-acting **benzodiazepine** primarily utilized in veterinary medicine as an **appetite stimulant** and **anxiolytic** in dogs and cats. **Clinical Pearls & Pharmacologic Advantages:** * **Metabolic Profile:** Unlike diazepam, oxazepam does not undergo Phase I hepatic metabolism (oxidation) and lacks active metabolites. It is metabolized solely via Phase II glucuronidation. * **Geriatric & Hepatic Safety:** Because of its simpler metabolic pathway, it is often considered a safer alternative to diazepam for geriatric patients or those with mild-to-moderate liver dysfunction. * **Feline Considerations:** Despite its favorable metabolic profile, its use in cats with hepatic lipidosis or severe liver dysfunction remains controversial due to rare, anecdotal reports of idiosyncratic fulminant hepatic failure. * **Behavioral Use:** It is used as an adjunctive oral anxiolytic for fears, phobias, and urine marking, though paradoxical excitation can occasionally occur.
Mechanism: Oxazepam acts as a positive allosteric modulator at the **GABA-A receptor** complex in the central nervous system. * **Binding:** It binds to specific benzodiazepine recognition sites on the **GABA-A** ligand-gated chloride channel. * **Mechanism:** It enhances the inhibitory effect of **gamma-aminobutyric acid (GABA)** by increasing the *frequency* of chloride channel openings. * **Pathway:** Influx of chloride ions โ **neuronal hyperpolarization** โ decreased neuronal excitability. * **Clinical Effect:** This depression of subcortical CNS levels (primarily limbic, thalamic, and hypothalamic) produces the characteristic anxiolytic, sedative, skeletal muscle relaxant, and anticonvulsant effects.
Dosing by species
- Appetite stimulant ยท 2 mg per cat (total dose) ยท PO ยท every 12 hours
- Appetite stimulant (hepatic lipidosis) ยท 0.1-0.3 mg/kg ยท PO ยท q12-24h ยท If cat has a small interest in eating
- Appetite stimulant ยท 0.25-0.5 mg/kg ยท PO ยท one to two times daily
- Fears and phobias ยท 1-2.5 mg per cat (total dose) ยท PO ยท every 12 hours
- Fears and phobias ยท 0.2-0.5 mg/kg ยท PO ยท q12-24h
- Feline urine marking ยท 0.2-0.5 mg/kg ยท PO ยท once to twice a day
- Spraying or overgrooming ยท 0.2-0.5 mg/kg ยท PO ยท q12-24h
- Fears and phobias ยท 0.2-1 mg/kg ยท PO ยท q12h or q6h ยท The lowest dose and longest frequency between doses that alleviate the fear should be used.
- Fears and phobias ยท 0.2-0.5 mg/kg ยท PO ยท q12-24h
- Fears and phobias ยท 0.2-1 mg/kg ยท PO ยท q12-24h
- Fears and phobias ยท 0.2-1 mg/kg ยท PO ยท one to two times a day
- Fears and phobias ยท 0.04-0.5 mg/kg ยท PO ยท q6h ยท The lowest dose and longest frequency between doses that alleviate the fear should be used.
Routes of administration
Contraindications
- Known benzodiazepine hypersensitivity
- Acute narrow angle glaucoma
Adverse effects
- Sedation (most common)
- Ataxia
- Paradoxical excitability, vocalization, or aggression
- Rebound anxiety or behavior worsening (if withdrawn abruptly)
- Rare precipitation of tonic-clonic seizures
- Rare idiosyncratic fulminant hepatic failure (cats)
Drug interactions
- CNS Depressant Drugs (barbiturates, narcotics, anesthetics) ยท Additive CNS depression effects may occur.
- Phenytoin ยท May decrease oxazepam concentrations.
- Probenecid ยท May impair glucuronide conjugation (in dogs) and prolong effects.
- Rifampin ยท May induce hepatic microsomal enzymes and decrease the pharmacologic effects of benzodiazepines.
- St. John's Wort ยท May decrease oxazepam effectiveness.
- Theophyllines ยท May decrease oxazepam effectiveness.
Monitoring
- Clinical efficacy (improved appetite, reduced anxiety/fear)
- Adverse effects (degree of sedation, ataxia, paradoxical excitement)
Overdose
**Signs of Toxicity:** When used alone, overdoses are generally limited to significant CNS depression (confusion, coma, decreased reflexes, profound sedation). **Treatment:** * **Decontamination:** Standard protocols for removing and/or binding the drug in the gut (e.g., emesis induction if asymptomatic and recent, activated charcoal) if taken orally. * **Supportive Care:** Systemic supportive measures (IV fluids, warming, respiratory support if needed). * **Antidote:** **Flumazenil** (a specific benzodiazepine antagonist) could potentially be used in life-threatening overdoses. * **Contraindications:** The use of analeptic agents (CNS stimulants such as caffeine, amphetamines) is generally not recommended.
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.