唑尼沙胺
唑尼沙胺是一種苯并異噁唑衍生物，屬於磺胺類抗癲癇藥物。在獸醫學中，主要用於犬貓難治性特發性癲癇的輔助治療或單一療法。 * **臨床重點**：由於其肝臟代謝負擔低於苯巴比妥，常被優先用於需要避免肝臟毒性的病患。 * 其在小動物體內具有良好的藥代動力學特性，犬的半衰期約為15小時（可每日給藥兩次），貓約為33小時（可每日給藥一次）。 * 與人類不同，唑尼沙胺在犬隻標準劑量下呈現線性藥代動力學。
作用機制: The exact mechanism of action is multifactorial and not completely elucidated: * Blocks **voltage-gated sodium channels** and reduces transient inward currents → stabilizes neuronal membranes and suppresses neuronal hypersynchronization. * Inhibits **T-type voltage-gated calcium channels**. * Acts as a weak **carbonic anhydrase inhibitor**. * *Note*: Unlike diazepam or phenobarbital, it does **not** appear to potentiate GABAergic activity.
各物種劑量
- Epilepsy (anecdotal) · 5 mg/kg PO every 12-24 hours · PO · q12-24h · Most commonly utilized anecdotal dose.
- Refractory to phenobarbital · 5-10 mg/kg PO once daily · PO · q24h · Long half-life makes once daily dosing likely appropriate.
- Epilepsy · 10-20 mg/kg PO once daily · PO · q24h
- Epilepsy · 5-10 mg/kg · PO · q24h · Long-term · Longer half-life in cats allows for once-daily dosing.
- Refractory epilepsy (with phenobarbital) · 5-10 mg/kg PO q12h · PO · q12h · The high end of the dose range is needed when used in combination with phenobarbital due to microsomal enzyme induction.
- Monotherapy · Initially at 5 mg/kg PO twice daily (q12h) · PO · q12h
- Add-on with phenobarbital · 10 mg/kg PO q12h · PO · q12h
- Initial monotherapy · 3-5 mg/kg PO q12h · PO · q12h
- Add-on agent · 10 mg/kg PO q12h · PO · q12h
- Epilepsy · 5-10 mg/kg PO q12h · PO · q12h · Gradual adaptation in dosing is recommended. Reduce phenobarbital doses by 25% at the time of starting zonisamide.
- Epilepsy (monotherapy or adjunctive) · 5-10 mg/kg · PO · q12h · Long-term · Start at 5 mg/kg q12h. If the dog is concurrently receiving phenobarbital, start at 10 mg/kg q12h due to induced metabolism.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Hypersensitivity to zonisamide
- Hypersensitivity to sulfonamide drugs
- Pregnancy (known teratogen in dogs)
- Hypersensitivity to sulfonamides
- Severe hepatic impairment
不良反應
- Sedation (usually transient)
- Ataxia
- Inappetence / Anorexia
- Vomiting
- Diarrhea
- Somnolence
- Keratoconjunctivitis sicca (KCS) - theoretical risk due to sulfonamide structure
- Polyarthropathy or blood dyscrasias - theoretical risk due to sulfonamide structure
- Sedation
- Anorexia
- Keratoconjunctivitis sicca (KCS)
- Hepatotoxicity (rare)
- Metabolic acidosis
藥物相互作用
- Phenobarbital · Increases the clearance of zonisamide. Repeated phenobarbital dosing decreases the bioavailability, peak concentrations, half-life, and AUC of zonisamide. This effect can persist up to 10 weeks after phenobarbital discontinuation. Higher zonisamide doses are typically required. · moderate
- Ketoconazole · May inhibit the hepatic metabolism of zonisamide, potentially increasing serum concentrations. · minor
監測
- Clinical efficacy (seizure frequency and severity)
- Serum zonisamide concentrations (suggested therapeutic range in dogs: 10-40 mcg/mL)
- Adverse effects (sedation, ataxia, GI upset)
- Schirmer tear test (monitor for KCS due to sulfonamide structure)
- Serum zonisamide concentrations (therapeutic target typically 10-40 µg/mL)
- Schirmer Tear Test (STT) periodically
- Liver enzymes and bilirubin
- Complete Blood Count (CBC)
過量
The LD50 of zonisamide in dogs is reportedly 1 gram/kg. In human overdoses, reported effects include **coma, bradycardia, hypotension, and respiratory depression**. **Treatment**: * GI evacuation if ingestion was recent. * Supportive and symptomatic therapy. * Because of the drug's long half-life, supportive care may be required for several days.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。