Misoprostol
Misoprostol is a synthetic **prostaglandin E1 (PGE1) analog** primarily utilized in veterinary medicine to prevent and treat gastric ulceration, particularly those induced by nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs inhibit cyclooxygenase (COX) enzymes, which depletes the protective prostaglandins in the gastric mucosa; misoprostol effectively replaces these depleted prostaglandins to restore mucosal defenses. Beyond its gastrointestinal applications, misoprostol possesses potent uterotonic properties. It increases uterine contractility and induces cervical relaxation, making it a valuable adjunctive therapy for reproductive indications such as **pregnancy termination**, **management of pyometra/metritis**, and post-mismating protocols. *Clinical Pearl:* While it has been investigated for atopic dermatitis and cyclosporine-induced nephrotoxicity, its use for these conditions is generally secondary due to modest efficacy and the prevalence of gastrointestinal side effects.
กลไกการออกฤทธิ์: 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**.
ขนาดยาตามชนิดสัตว์
- 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
วิธีการให้ยา
ข้อห้ามใช้
- 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)
อาการไม่พึงประสงค์
- Diarrhea
- Abdominal pain
- Vomiting
- Flatulence
- Uterine contractions (in females)
- Vaginal bleeding (in females)
- Diarrhoea
- Nausea
- Abortion
อันตรกิริยาระหว่างยา
- 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
การติดตาม
- 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)
การได้รับยาเกินขนาด
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).
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