奧美拉唑
奧美拉唑 (Omeprazole) 是一種高效的**質子幫浦抑制劑 (PPI)**，在獸醫學中廣泛用於治療和預防胃十二指腸潰瘍與糜爛。 * **卓越的療效：** 在提高胃內 pH 值和預防運動誘發的胃炎（如阿拉斯加雪橇犬的研究所示）方面，通常被認為優於 H2 受體拮抗劑（如法莫替丁）。 * **馬匹應用：** 口服糊劑配方專門用於治療和預防馬匹胃潰瘍 (EGUS)，且效果顯著。 * **廣泛應用：** 適用於多種動物（包括犬、貓、雪貂和豬），用於處理尿毒症性胃病、食道炎、幽門螺旋桿菌感染以及非類固醇消炎藥 (NSAID)/皮質類固醇引起的潰瘍。 > **臨床要點：** 由於奧美拉唑需要酸性環境來活化，但在吸收前會被胃酸破壞，因此人類口服製劑均帶有腸溶衣。**絕對不可壓碎或咀嚼**，否則會破壞藥物的生物利用度。
作用機制: Omeprazole is a **prodrug** that acts as a substituted benzimidazole gastric acid pump inhibitor. 1. **Absorption & Distribution:** After absorption, it diffuses from the blood into the highly acidic secretory canaliculi of the gastric **parietal cells**. 2. **Activation:** In this acidic environment (pH < 3), it is protonated and rearranged into its active form, a **sulphenamide derivative**. 3. **Irreversible Binding:** The active sulphenamide binds **irreversibly** via disulfide bonds to the **H⁺/K⁺ ATPase enzyme** (the proton pump) at the secretory surface. 4. **Acid Suppression:** This blocks the final common pathway of gastric acid secretion, inhibiting the transport of hydrogen ions into the stomach lumen during both basal and stimulated conditions. > **Pharmacological Note:** Because the binding is irreversible, acid secretion only resumes when new H⁺/K⁺ ATPase enzymes are synthesized. This explains why its duration of action (24-72 hours) far outlasts its short plasma half-life (~1 hour). Omeprazole also inhibits the hepatic **cytochrome P-450** mixed-function oxidase system, which can lead to drug interactions.
各物種劑量
- Adjunctive treatment of esophagitis or gastric ulcers · 0.5-1 mg/kg PO q24h · PO · q24h
- GI ulcer management/prevention · 0.7-1.5 mg/kg PO q12-24h · PO · q12h-q24h
- Adjunctive treatment of uremic gastropathy · 0.7 mg/kg PO q24h · PO · q24h · Dosage may need to be modified in moderate or severe renal failure.
- Short-term treatment of gastroenteritis · 0.7 mg/kg PO q24h · PO · q24h · Short-term
- Treatment of gastric ulcers · 4 mg/kg PO once daily for 4 weeks; to prevent recurrence treat for at least another 4 weeks at 2 mg/kg PO once daily · PO · q24h · 8 weeks total · ARCI UCGFS Class 5 Drug
- Foals: Preventative dose · 1 mg/kg PO q24h · PO · q24h · There has been a recent shift to not administering prophylactic antiulcer medication routinely to sick foals.
- Foals: Treatment dose · 4 mg/kg PO q24h · PO · q24h · Will reduce gastric pH in a few hours.
- Treatment or prophylaxis of gastric ulcers in foals · 4 mg/kg PO once daily for treatment, 1-2 mg/kg PO once daily for prophylaxis · PO · q24h
- Foals: Gastric ulcers · 4 mg/kg PO q24h · PO · q24h · Commonly foals will be started on ranitidine (1.5 mg/kg IV q8h; 6.6 mg/kg PO q8h) and omeprazole together.
給藥途徑
禁忌症
- Known hypersensitivity to omeprazole
不良反應
- GI distress (anorexia, colic, nausea, vomiting, flatulence, diarrhea)
- Hematologic abnormalities (rare)
- Urinary tract infections
- Proteinuria
- CNS disturbances
- Urticaria (rare in horses)
藥物相互作用
- Benzodiazepines (e.g., diazepam) · Omeprazole may potentially alter benzodiazepine metabolism and prolong CNS effects
- Clarithromycin · Increased levels of omeprazole, clarithromycin and 14-hydroxyclarithromycin are possible
- Cyanocobalamin (oral) · Omeprazole may decrease oral absorption
- Cyclosporine · Omeprazole may reduce cyclosporine metabolism
- Ketoconazole, Itraconazole, Iron, Ampicillin esters · Omeprazole increases gastric pH, which may decrease the absorption of these drugs that require an acidic environment
- Warfarin · Omeprazole may increase anticoagulant effect
監測
- Clinical efficacy (resolution of clinical signs of ulcers/esophagitis)
- Adverse effects (GI distress)
- Liver enzymes (may increase)
- Serum gastrin levels (will increase early in therapy)
過量
The LD50 in rats after oral administration is reportedly >4 grams/kg. Humans have tolerated oral dosages of 360 mg/day without significant toxicity. Should a massive overdose occur, treat symptomatically and supportively. Due to its wide safety margin, acute toxicity from accidental ingestion is generally mild.
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