二甲雙胍
**二甲雙胍 (Metformin)** 是一種雙胍類口服降血糖藥物，在人類醫學中廣泛用於治療第二型糖尿病。在獸醫學中，其使用極具爭議，且通常被認為療效有限。 * **貓**：曾被研究作為非胰島素依賴型糖尿病 (NIDDM) 的輔助治療。然而，臨床成功率極低，且由於胃腸道毒性，動物通常耐受性不佳。部分獸醫內分泌學家強烈建議不要在貓身上使用。 * **馬**：曾被研究用於控制馬代謝症候群 (EMS) 和胰島素失調。不幸的是，二甲雙胍在馬體內的藥代動力學特徵極不理想，口服生物利用度極低（約 4-7%）且消除半衰期非常快，使其全身性療效受到質疑。 > **臨床要點**：與磺醯脲類（如格列吡嗪）或胰島素不同，二甲雙胍不會刺激胰臟釋放胰島素，因此單獨使用時極少引起低血糖。
作用機制: Metformin acts primarily as an **insulin sensitizer** and inhibitor of hepatic glucose output. Its actions are multifaceted: * **AMPK Activation**: Metformin activates **AMP-activated protein kinase (AMPK)** in hepatocytes → **decreases hepatic gluconeogenesis** (glucose production). * **Peripheral Sensitization**: Increases insulin's ability to transport glucose across cell membranes in skeletal muscle → **increases peripheral glucose uptake**. * **Intestinal Absorption**: May decrease the intestinal absorption of dietary glucose. * **Advanced Glycosylation**: Inhibits the formation of advanced glycosylation end-products. Because it does not stimulate insulin production or release from pancreatic beta cells, it does not directly induce hypoglycemia.
各物種劑量
- Non-insulin dependent diabetes mellitus (NIDDM) · 50 mg (total dose) per cat PO twice daily · PO · q12h · May be efficacious only in cats with detectable concentrations of insulin at time of treatment.
- Early NIDDM · 2 mg/kg PO q12h · PO · q12h
- General Use Warning · Not recommended · PO · Author states 'metformin has been shown toxic to cats and should not be used. It is also ineffective.'
- General · 100-500 mg/L of drinking water · PO · Continuous
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- Hypersensitivity to metformin
- Renal dysfunction
- Metabolic acidosis
- Concurrent use of parenteral iodinated contrast agents (temporary contraindication)
不良反應
- Lethargy
- Inappetence
- Vomiting
- Diarrhea
- Weight loss
- Lactic acidosis (rare but severe)
藥物相互作用
- ACE Inhibitors · May increase risk for hypoglycemia
- Cimetidine · Can cause a 60% increase in peak metformin plasma levels and a 40% increase in AUC
- Corticosteroids · May reduce hypoglycemic efficacy
- Diuretics, Thiazide · May reduce hypoglycemic efficacy
- Furosemide · Can increase the AUC and plasma levels of metformin by 22%; metformin can decrease the peak plasma concentrations and AUC of furosemide
- Iodinated Contrast Agents (Parenteral) · May cause acute renal failure and lactic acidosis if used within 48 hours of a metformin dose
- Isoniazid · May reduce hypoglycemic efficacy
- Sympathomimetic Agents · May reduce hypoglycemic efficacy
監測
- Fasting blood glucose
- Appetite and attitude
- Body condition
- PU/PD resolution
- Serum fructosamine and/or glycosylated hemoglobin levels
- Renal function (baseline and annually)
- Adverse effects (especially GI signs)
過量
**Overdose & Toxicity Profile:** * **Small Animals**: Hypoglycemia is **not commonly seen** in overdoses of metformin alone. However, the drug has a narrow margin of safety regarding gastrointestinal upset. * **Clinical Signs**: Vomiting and diarrhea are the most common findings in dogs and cats following accidental ingestion. * **Human Data**: Massive overdoses (e.g., 100 grams) caused hypoglycemia only 10% of the time, but **lactic acidosis** occurred. Lactic acidosis has been seen in human overdoses of 7 to 20 grams. It is unknown at what exact dose acidosis may occur in domestic animals. > **Management**: Treatment is largely supportive and symptomatic, focusing on managing GI distress and monitoring acid-base status and renal function.
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。