プリミドン

動物種別の用量

用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。

投与経路

禁忌

• Severe liver disease
• Demonstrated previous hypersensitivity to primidone or barbiturates
• Nephritis (large doses contraindicated)
• Severe respiratory dysfunction (large doses contraindicated)
• Cats (considered contraindicated by many clinicians due to high toxicity risk)

有害事象

• Anxiety and agitation (especially during initiation)
• Elevated liver enzymes (ALT, ALP, GLDH)
• Decreased serum albumin
• Hepatic lipidosis
• Hepatocellular hypertrophy and necrosis
• Extramedullary hematopoiesis
• Depression and sedation
• Ataxia
• Polydipsia (PD)
• Polyuria (PU)
• Polyphagia
• Anorexia
• Tachycardia
• Dermatitis
• Episodic hyperventilation
• Urolith formation (primidone uroliths reported)
• Megaloblastic anemia (rare)

薬物相互作用

• Acetaminophen · Increased risk for hepatotoxicity, particularly with large or chronic doses of barbiturates.
• Carbonic Anhydrase Inhibitors (e.g., acetazolamide) · Oral administration may decrease the GI absorption of primidone.
• Monoamine Oxidase Inhibitors (e.g., amitraz, selegiline) · May prolong phenobarbital effects.
• Phenytoin · Barbiturates may affect phenytoin metabolism, and phenytoin may alter barbiturate levels; therapeutic monitoring indicated.
• Rifampin · May induce enzymes that increase the metabolism of barbiturates.
• Antihistamines · May increase the CNS depressant effects of phenobarbital.
• Chloramphenicol · May increase the effects of phenobarbital; phenobarbital may also decrease chloramphenicol levels.
• Opiates · May increase the CNS depressant effects of phenobarbital.
• Phenothiazines · May increase the effects of phenobarbital; phenobarbital may decrease phenothiazine serum concentrations.
• Valproic Acid · May increase the effects of phenobarbital.
• Warfarin · Phenobarbital may decrease anticoagulant effects by lowering serum concentrations.
• Beta-blockers · Phenobarbital may decrease effects by lowering serum concentrations.

モニタリング

• Anticonvulsant efficacy (seizure frequency and severity)
• Adverse effects (CNS depression, PU/PD, weight gain, signs of liver disease)
• Serum phenobarbital levels (therapeutic range in dogs thought to be 15-40 mcg/mL) if lack of efficacy or adverse reactions are noted
• Routine CBCs and liver enzyme panels at least every 6 months during chronic therapy

過量投与

**Clinical Signs:** Because primidone is rapidly metabolized to phenobarbital in dogs, signs of acute toxicity mirror barbiturate overdose: sedation progressing to coma, anorexia, vomiting, ataxia, and nystagmus. **Treatment:** * **Decontamination:** Removal of ingested product from the gut if appropriate (emesis or gastric lavage). * **Adsorbents:** **Activated charcoal** is of considerable benefit in enhancing the clearance of phenobarbital (acts as a 'sink' for the drug to diffuse from the vasculature back into the gut), even if the drug was administered parenterally. * **Supportive Care:** Provide respiratory and cardiovascular support. * **Enhanced Elimination:** Forced alkaline diuresis can augment elimination in patients with normal renal function. Peritoneal dialysis or hemodialysis may be helpful in severe intoxications or anuric patients.