ミソプロストール
ミソプロストールは合成**プロスタグランジンE1（PGE1）アナログ**であり、獣医療においては主に非ステロイド性抗炎症薬（NSAIDs）によって誘発される胃潰瘍の予防および治療に使用されます。 NSAIDsはシクロオキシゲナーゼ（COX）酵素を阻害し、胃粘膜の保護的なプロスタグランジンを減少させますが、ミソプロストールはこれらの枯渇したプロスタグランジンを効果的に補充し、粘膜防御を回復させます。 胃腸への応用に加え、ミソプロストールは強力な子宮収縮作用を持っています。子宮の収縮力を高め、子宮頸管の弛緩を誘発するため、**妊娠中絶**、**子宮蓄膿症/子宮炎の管理**、および交尾後の処置などの生殖器系の適応症に対する有用な補助療法となります。 *臨床のポイント:* アトピー性皮膚炎やシクロスポリン誘発性腎毒性に対する使用も研究されていますが、有効性が控えめであることと胃腸の副作用が多いため、これらの状態に対する使用は通常二次的なものです。
作用機序: Misoprostol exerts its effects through multiple prostaglandin (EP) receptors across different organ systems: * **Gastric Acid Suppression:** Binds directly to **EP3 receptors** on gastric parietal cells → inhibits adenylate cyclase → decreases intracellular cAMP → reduces the activity of the apical H+/K+ ATPase proton pump → **decreased basal and stimulated gastric acid secretion**. * **Gastric Cytoprotection:** Binds to **EP receptors** on superficial foveolar epithelial cells → stimulates the secretion of protective **mucin and bicarbonate**. It also increases mucosal blood flow and accelerates epithelial cell turnover, enhancing the overall mucosal barrier and healing capacity. * **Reproductive Tract:** Binds to **EP receptors** in the myometrium → increases intracellular calcium concentrations → increases the amplitude and frequency of **uterine contractions**. It also induces collagen breakdown in the cervix, leading to **cervical softening and dilation**.
動物種別の用量
- Induction of abortion · Dose not specified in text · PO · Not specified · Not specified · Used in combination with aglepristone
- Adjunctive treatment of acute colitis · 5 micrograms/kg · PO · q8h · Route not listed in original source; assumed PO by Plumb.
- Equine gastric ulcer syndrome · 5 micrograms/kg · PO · q8h
- Induce cervical relaxation (post-breeding endometritis) · 1000 micrograms (total dose) · topical · once · Applied as a compounded cream to the caudal os and lumen of the cervix after lavage. Oxytocin (20 Units IM) administered immediately following lavage and again every 6 hours until the following morning.
- Prevention of aspirin-induced gastric injury · 3 micrograms/kg · PO · q12h or q8h · Study suggests q12h is as effective as q8h.
- Prevention or treatment of gastric ulceration from NSAIDs · 2-5 micrograms/kg · PO · four times daily · Uncertain if it improves healing of established ulcers; no distinct advantage over other antacids for non-NSAID ulcers.
- Prevention or treatment of gastric ulceration from NSAIDs · 2-5 micrograms/kg · PO · q8-12h
- Preventing GI mucosal injury in dogs with arthritis requiring long-term NSAID therapy; treating gastro-duodenal ulcer disease caused by NSAIDS · 3 micrograms/kg · PO · three times a day
投与経路
禁忌
- Pregnancy (unless being used specifically as an abortifacient)
- Nursing mothers (can cause severe diarrhea in nursing offspring)
- Known sensitivity to prostaglandins or prostaglandin analogs
- Pregnant animals (unless being used specifically to induce abortion)
有害事象
- Diarrhea
- Abdominal pain
- Vomiting
- Flatulence
- Uterine contractions (in females)
- Vaginal bleeding (in females)
- Diarrhoea
- Nausea
- Abortion
薬物相互作用
- Magnesium-containing antacids · May aggravate misoprostol-induced diarrhea. If an antacid is required, an aluminum-only antacid is preferred.
- Gentamicin · May exacerbate renal dysfunction · moderate
- Diclofenac · Human combination products (misoprostol + diclofenac) are highly toxic to small animals due to different NSAID pharmacokinetics · major
モニタリング
- Clinical efficacy (resolution of ulcer signs, successful pregnancy termination, etc.)
- Adverse effects (GI distress, diarrhea, vomiting)
- Vaginal bleeding or discharge (if used in females)
- Resolution of clinical signs of gastric ulceration (e.g., vomiting, melena, anorexia)
- Monitoring for adverse GI effects (diarrhoea, abdominal pain)
過量投与
Information on acute toxicity is limited. Overdoses in laboratory animals have produced: * Diarrhea and emesis * GI lesions * Tremors and seizures * Focal cardiac, hepatic, or renal tubular necrosis * Hypotension **Treatment:** Overdoses should be treated seriously. Employ standard gut-emptying techniques (e.g., emesis induction, activated charcoal) when applicable and safe. Treat resultant toxicity symptomatically with supportive care (e.g., IV fluids for hypotension and GI fluid loss).
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。