胰島素
胰島素是一種由胰島β細胞產生的關鍵胜肽激素。它是獸醫學中治療糖尿病和糖尿病酮酸中毒 (DKA) 的基石。 製劑根據其起效和持續時間大致分類： * **短效 (常規 Regular, 賴脯 Lispro)：** 主要用於醫院環境中 DKA 或嚴重高血鉀的急性穩定。常規胰島素是唯一可以靜脈注射的劑型。 * **中效 (NPH, 豬鋅 Lente)：** 常見於犬隻的維持治療。豬胰島素在結構上與犬胰島素完全相同，可將抗胰島素抗體形成的風險降至最低。 * **長效 (PZI, 甘精 Glargine, 地特 Detemir)：** 常用於貓的維持治療，因為貓代謝胰島素的速度比狗快。 > **臨床要點：** 貓糖尿病通常類似於人類的第2型糖尿病，透過早期積極使用長效胰島素（如甘精胰島素）並配合低碳水化合物飲食，可能會進入緩解期。犬糖尿病通常類似於人類的第1型糖尿病，需要終身注射外源性胰島素。
作用機制: Insulin initiates its action by binding to the **tyrosine kinase insulin receptor** on the cell membrane. **Mechanism Pathway:** Receptor binding → Autophosphorylation → Activation of **Insulin Receptor Substrates (IRS)** → Activation of the **PI3K/Akt pathway** → Translocation of **GLUT4** transport proteins to the cell surface → Rapid facilitated diffusion of glucose into skeletal muscle and adipose tissue. **Metabolic Effects:** * **Carbohydrate metabolism:** Promotes cellular glucose uptake and hepatic glycogenesis; inhibits glycogenolysis and gluconeogenesis. * **Lipid metabolism:** Stimulates lipogenesis and potently inhibits lipolysis and ketogenesis (crucial for resolving DKA). * **Protein metabolism:** Increases amino acid uptake and protein synthesis. * **Electrolyte shift:** Drives potassium and magnesium into the intracellular space (utilized therapeutically for life-threatening hyperkalemia).
各物種劑量
- Diabetic ketoacidosis (Regular insulin) · Same protocol using regular insulin as described for dogs · IM, IV, SC · Varies · Until stabilized
- Diabetic ketoacidosis (Glargine) · 2 Units per cat SC and 1 Unit per cat IM (regardless of body weight) initially; repeat the IM dose 4 or more hours later if BG > 250-290 mg/dL; repeat the SC dose every 12 hours. · SC and IM · Initially, then q12h SC · Until stabilized
- Severe hyperkalemia · 0.5 to 1 Unit/kg IM regular insulin plus 2 grams dextrose per unit of insulin IV · IM · Once
- Uncomplicated diabetes mellitus (Glargine, Detemir, or PZI) · Blood glucose <360 mg/dL: 0.25 Units/kg of ideal body weight SC every 12 hours; Blood glucose >=360 mg/dL: 0.5 Units/kg of ideal body weight SC every 12 hours · SC · q12h · Lifelong · If no monitoring in first week, begin with 1 Unit per cat every 12 hours.
- Uncomplicated diabetes mellitus (ProZinc) · 0.2-0.7 Units/kg SC every 12 hours given concurrently with or right after a meal · SC · q12h · Lifelong · Goal: glucose nadir between 80 & 150 mg/dL.
- Uncomplicated diabetes mellitus (Vetsulin) · 0.5 Units/kg SC once daily · SC · q24h · Lifelong
- Uncomplicated diabetes mellitus (Lente) · 1 Unit per cat SC twice daily for cats <4kg & 1.5-2 Units/cat twice daily for cats >4kg. Alternatively: 0.25 Units/kg SC twice daily if BG 216-342 mg/dL; 0.5 Units/kg SC twice daily if BG>360mg/dL. · SC · q12h · Lifelong
- Diabetes mellitus · 0.5-1 Unit per ferret SC twice daily. Alternatively: 0.1-0.5 Units/kg IM or SC twice daily to start; adjust to optimal dose. · SC, IM · q12h · Lifelong · May require insulin to be diluted.
給藥途徑
禁忌症
- Episodes of hypoglycemia (absolute contraindication)
- Systemic allergy to pork or pork products (specifically for Vetsulin/porcine lente)
不良反應
- Hypoglycemia (most common and potentially life-threatening)
- Insulin-induced hyperglycemia ('Somogyi effect' due to counter-regulatory hormone release following hypoglycemia)
- Insulin antagonism or resistance
- Rapid insulin metabolism
- Local hypersensitivity reactions to 'foreign' proteins
- Lipodystrophy at the injection site (if sites are not rotated)
藥物相互作用
- Beta-adrenergic blockers (e.g., propranolol) · Can have variable effects on glycemic control and can mask the clinical signs associated with hypoglycemia.
- Clonidine, Reserpine · Can mask the signs associated with hypoglycemia.
- Digoxin · Insulin alters serum potassium levels; concurrent use requires close monitoring for cardiac arrhythmias, especially with concurrent diuretics.
- Alcohol, Anabolic steroids, ACE inhibitors, Aspirin, Disopyramide, Fluoxetine, MAOIs, Somatostatin derivatives, Sulfonamides · May potentiate the hypoglycemic activity of insulin.
- Calcium channel blockers, Corticosteroids, Danazol, Diuretics, Isoniazid, Niacin, Phenothiazines, Thyroid hormones · May decrease the hypoglycemic activity of insulin (cause insulin resistance).
監測
- Blood glucose (serial curves or continuous monitoring)
- Patient weight
- Appetite and water intake
- Urine output
- Blood or urine ketones (if DKA suspected)
- Fructosamine (goal <450 micromol/L) or glycosylated hemoglobin
過量
Overdosage of insulin leads to **hypoglycemia**, which can be rapidly fatal or cause permanent brain damage if untreated. **Clinical Signs:** * Weakness, lethargy, ataxia * Shaking, muscle fasciculations * Head tilting, bizarre behavior, blindness * Restlessness, extreme hunger * Seizures and coma **Treatment:** * **Mild:** Offer the animal its usual food. * **Severe (e.g., seizures):** Rub oral dextrose solutions (e.g., **Karo® syrup**) on the oral mucosa (do not pour down the throat to avoid aspiration). * **Veterinary Intervention:** Intravenous injections of 50% dextrose solutions (small amounts, slowly administered—usually 2-15 mL). * **Monitoring:** Once alleviated (usually within 1-2 minutes), monitor closely with serial blood glucose levels to prevent recurrence (especially with long-acting insulins) and adjust future doses.
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