茶鹼
**茶鹼 (Theophylline)** 是一種甲基黃嘌呤類支氣管擴張劑，主要用於治療犬貓的小氣道疾病。它能擴張支氣管、促進黏液纖毛清除、刺激呼吸中樞、增加對PaCO2的敏感性、增加膈肌收縮力、穩定肥大細胞，並具有輕微的正性肌力作用。它也作為解痙劑並具有輕微的利尿作用。 > **臨床警告：** 茶鹼的**治療指數低**（治療血漿濃度為 5-20 µg/ml）。必須根據**瘦體重 (lean body weight)** 給藥以避免中毒。
作用機制: Causes inhibition of **phosphodiesterase** enzymes and antagonism of **adenosine** and prostaglandin receptors → increased intracellular cAMP → smooth muscle relaxation and **bronchodilation**. It also alters intracellular calcium and stimulates catecholamine release, providing mild inotropic and diuretic effects.
各物種劑量
- Bronchodilation · 20 mg/kg or 10-15 mg/kg · PO · q24h or q12h · Continuous · 20 mg/kg p.o. q24h or 10 mg/kg p.o. q12h which may be increased to 15 mg/kg p.o. q12h if no side effects on lower dose. Manufacturer only recommends q24h dosing. Some texts indicate q12h dosing of the sustained-release preparation is required to maintain therapeutic serum levels.
- Bronchodilation · 15-19 mg/kg · PO · q24h · Continuous · Sustained-release preparation.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- Patients with a known history of arrhythmias
- Patients with a known history of seizures
不良反應
- Vomiting
- Diarrhoea
- Polydipsia
- Polyuria
- Reduced appetite
- Tachycardia
- Arrhythmias
- Nausea
- Twitching
- Restlessness
- Agitation
- Excitement
- Convulsions
- Hyperaesthesia (cats)
藥物相互作用
- Cimetidine · May increase serum levels of theophylline · major
- Diltiazem · May increase serum levels of theophylline · moderate
- Erythromycin · May increase serum levels of theophylline · moderate
- Fluoroquinolones · May increase serum levels of theophylline · moderate
- Allopurinol · May increase serum levels of theophylline · moderate
- Phenobarbital · May decrease serum concentration of theophylline · moderate
- Pancuronium · Theophylline may decrease the effects of pancuronium · moderate
- Beta-adrenergic blockers (e.g., propranolol) · May antagonize each other's effects · moderate
- Halothane · Increased incidence of cardiac dysrhythmias · major
- Ketamine · Increased incidence of seizures · major
監測
- Serum theophylline concentrations (therapeutic target: 5-20 µg/ml)
- Heart rate and rhythm
- Clinical signs of toxicity (vomiting, agitation, seizures)
過量
**Clinical Pearl:** Overdose leads to severe arrhythmias, seizures, vomiting, and hypokalemia. Treatment is supportive: perform gastric decontamination if ingestion was recent, control seizures with diazepam or phenobarbital, treat arrhythmias as indicated, and monitor electrolytes closely.
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