丹曲林鈉
丹曲林鈉是一種獨特的直接作用型**骨骼肌鬆弛劑**。與中樞作用的肌肉鬆弛劑（如美索巴莫或地西泮）不同，它直接作用於周邊肌肉纖維。 在獸醫學中，其主要適應症包括： * **惡性高熱 (MH)：** 針對豬隻和犬隻惡性高熱及豬緊迫症候群的救命藥物。 * **馬匹肌肉病變：** 廣泛用於馬匹以預防和治療**勞力性橫紋肌溶解症**（「綁住」症候群）及**麻醉後肌炎 (PAM)**。 * **小動物泌尿科：** 常用於降低犬貓尿道外括約肌張力，以治療**功能性尿道阻塞**。 * **毒素咬傷：** 建議作為**黑寡婦蜘蛛咬傷**的輔助治療，因該毒素會引起大量乙醯膽鹼釋放及嚴重的肌肉痙攣。 **臨床要點：** 由於注射劑型極為昂貴且重配後保存期限短，通常僅保留用於嚴重、急性的危機（如惡性高熱），而口服劑型則用於慢性管理或預防。
作用機制: Dantrolene acts intracellularly to uncouple the excitation-contraction process in skeletal muscle. * It binds specifically to the **ryanodine receptor (RyR1)** located on the **sarcoplasmic reticulum (SR)**. * This binding **blocks the release of calcium (Ca²⁺)** from the SR into the myoplasm. * Decreased intracellular calcium → prevents the interaction of actin and myosin → produces **skeletal muscle relaxation**. Because it specifically targets the RyR1 isoform (found primarily in skeletal muscle) rather than RyR2 (cardiac muscle), it has minimal direct effects on cardiac or smooth muscle at standard therapeutic doses. The exact mechanism for its mild CNS effects (drowsiness, dizziness) remains poorly understood.
各物種劑量
- Treatment of functional urethral obstruction due to increased external urethral tone · 0.5-2 mg/kg PO q12h OR 0.5-1 mg/kg IV · PO/IV · q12h · IV product very expensive.
- Treatment of functional urethral obstruction due to increased external urethral tone · 0.5-2 mg/kg PO three times daily · PO · TID
- Treatment of functional urethral obstruction due to increased external urethral tone · 2-10 mg (total dose) PO three times daily · PO · TID · Given with either prazosin (0.5 mg/cat once to twice daily) or phenoxybenzamine (2.5-7.5 mg/cat once to twice daily).
- Treatment of functional urethral obstruction due to increased external urethral tone · 0.5-1 mg/kg PO q12h · PO · q12h
- Treatment of acute rhabdomyolysis · 15-25 mg/kg slow IV four times daily · IV · QID
- Treatment of acute rhabdomyolysis · 2-4 mg/kg PO via nasogastric tube once daily · PO · SID
- Prevention of recurrent exertional rhabdomyolysis in Thoroughbreds · 4 mg/kg PO in horses fasted (12-hour fast in study) prior to administration. · PO · Once
- Prevention of rhabdomyolysis · 2 mg/kg PO once daily for 3-5 days and then every 3rd day for a month · PO · SID then q3d · 1 month · Drug is diluted in normal saline and given via stomach tube. Monitor hepatic function.
- Prevention of rhabdomyolysis · 300 mg (total dose) PO once daily · PO · SID · May be preferable because the drug is hepatotoxic.
給藥途徑
禁忌症
- Preexisting liver disease (use with extreme caution)
- Severe cardiac dysfunction (use with caution)
- Pulmonary disease (use with caution)
不良反應
- Weakness
- Sedation
- Dizziness
- Headache
- Nausea
- Vomiting
- Constipation
- Increased urinary frequency
- Hypotension
- Hepatotoxicity (especially with chronic use)
藥物相互作用
- Benzodiazepines & other CNS depressants · Increased sedation may be seen if tranquilizing agents are used concomitantly.
- Calcium-Channel Blockers · Rare reports of cardiovascular collapse in humans; concomitant use during malignant hyperthermia crises is not recommended. · major
- Estrogens · Increased risks of hepatotoxicity have been seen in women >35 years of age; veterinary significance is unknown.
- Warfarin · Dantrolene may be displaced from plasma proteins by warfarin, resulting in increased effects or adverse reactions.
監測
- Baseline and periodic liver function tests (ALT, AST, Alk Phos, etc.) if projecting to be used chronically or using high dosages
- Body temperature (especially for malignant hyperthermia)
- Urine volume, frequency, continence
過量
There is no specific antidotal therapy for dantrolene overdoses. * **Decontamination:** Remove the drug from the gut if possible (e.g., emesis induction, activated charcoal) if exposure was recent and oral. * **Supportive Care:** Treat supportively, monitoring respiratory, cardiovascular, and hepatic function.
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