シメチジン
**シメチジン**はヒスタミン（H2）受容体拮抗薬であり、特発性、尿毒症性、または薬剤性のびらん性胃炎、胃・十二指腸潰瘍、食道炎、およびガストリノーマ、肥満細胞腫、短腸症候群に続発する胃酸分泌過多の管理に使用されます。 > **臨床上の警告：** NSAID誘発性潰瘍に対する有効性は議論の余地があります。より新しいH2ブロッカー（ファモチジンなど）やプロトンポンプ阻害薬（オメプラゾールなど）と比較して、胃酸分泌を抑える効果は弱いです。消化管運動促進作用はごくわずかであり、制吐作用はありません。
作用機序: 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.
動物種別の用量
- 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.
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
- No specific contraindications available, but use with caution in patients with known hypersensitivity.
有害事象
- 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)
薬物相互作用
- 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
モニタリング
- 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)
過量投与
Adverse reactions are generally minor even at high doses. Supportive care should be provided if massive overdose occurs.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。