西咪替丁
**西咪替丁 (Cimetidine)** 是一種組織胺 (H2) 受體拮抗劑，用於治療特發性、尿毒症或藥物引起的糜爛性胃炎、胃和十二指腸潰瘍、食道炎，以及繼發於胃泌素瘤、肥大細胞腫瘤或短腸症候群的胃酸分泌過多症狀。 > **臨床警告：** 其對非類固醇抗發炎藥 (NSAID) 引起的潰瘍療效尚存爭議。與較新型的H2受體阻斷劑（如法莫替丁）和質子幫浦抑制劑（如奧美拉唑）相比，其降低胃酸的效果較弱。它具有極微弱的促腸胃蠕動作用，且不具備止吐效果。
作用機制: Acts as a **Histamine (H2) receptor antagonist** → competitively inhibits histamine at H2 receptors of the gastric parietal cells → reduces histamine-induced gastric acid secretion. It also binds to microsomal **cytochrome P450** enzymes, retarding oxidative hepatic drug metabolism. It has weak anti-androgenic effects.
各物種劑量
- All uses (gastritis, ulcers, oesophagitis, hypersecretory conditions) · 2.5-5 mg/kg · PO/IV/IM · q12h · Taper upon cessation · Administer IV over 30 minutes. Reduce dose in renal impairment.
- All uses (gastritis, ulcers, oesophagitis, hypersecretory conditions) · 5 mg/kg · PO/IV/IM · q8h · Taper upon cessation · Administer IV over 30 minutes. Reduce dose in renal impairment.
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
- No specific contraindications available, but use with caution in patients with known hypersensitivity.
不良反應
- Thrombocytopenia (reported in dogs)
- Transient and self-resolving slight swelling of mammary glands (female dogs)
- Hepatotoxicity (rare, reported in humans)
- Nephrotoxicity (rare, reported in humans)
- Headache (humans)
- Decreased libido (humans)
藥物相互作用
- Propranolol · Increases plasma levels of beta-blockers due to CYP450 inhibition · moderate
- Verapamil · Increases plasma levels of calcium-channel blockers · moderate
- Diazepam · Increases plasma levels of diazepam · moderate
- Lidocaine · Increases plasma levels of lidocaine · major
- Metronidazole · Increases plasma levels of metronidazole · moderate
- Pethidine · Increases plasma levels of pethidine · moderate
- Theophylline · Increases plasma levels of theophylline · major
- Myelosuppressive agents · May exacerbate leucopenia · moderate
- Sucralfate · May decrease cimetidine bioavailability; administer sucralfate at least 2 hours before · minor
- Antacids · May decrease absorption; stagger oral doses by 2 hours · minor
- Digoxin · Altered absorption/metabolism; stagger oral doses by 2 hours · moderate
- Itraconazole · Decreased absorption of itraconazole due to reduced gastric acidity; stagger oral doses by 2 hours · moderate
- Maropitant · Potential interaction; stagger oral doses by 2 hours · minor
監測
- Clinical signs of GI ulceration or bleeding
- Renal function (to guide dose reduction if impaired)
- Heart rate and blood pressure (if administering IV)
- Complete blood count (monitor for thrombocytopenia or leucopenia, especially if on concurrent myelosuppressive drugs)
過量
Adverse reactions are generally minor even at high doses. Supportive care should be provided if massive overdose occurs.
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。