米爾貝肟
米爾貝肟（Milbemycin oxime）是一種**巨環內酯類抗寄生蟲藥**，廣泛應用於獸醫學。 - **主要用途**：每月預防心絲蟲（*Dirofilaria immitis*）及控制腸道寄生蟲（鉤蟲、蛔蟲、鞭蟲）。 - **標籤外用途**：治療全身性毛囊蟲症、疥癬蟲、姬螯蟎及鼻蟎。 > **臨床提示**：雖然通常很安全，但對於帶有 **ABCB1 (MDR1) 基因突變** 的犬種（如牧羊犬、澳洲牧羊犬、喜樂蒂等），若為了治療毛囊蟲而使用高劑量每日給藥時，需特別注意神經毒性風險。對於這些犬種，它通常被認為是比伊維菌素（ivermectin）更安全的替代品，但在開始高劑量治療前仍建議進行基因檢測。
作用機制: Milbemycin acts primarily on the nervous system of invertebrates. - Binds to **glutamate-gated chloride channels** and **GABA receptors** in the parasite's nervous system. - This binding increases membrane permeability to chloride ions → **hyperpolarization** of nerve and muscle cells. - Results in flaccid paralysis and death of the parasite. *Note*: Mammals are generally protected because their GABA receptors are confined to the central nervous system, and intact P-glycoprotein (P-gp) pumps at the blood-brain barrier prevent the drug from accumulating in the CNS.
各物種劑量
- Prevention of heartworm; treat adult hookworm and adult roundworms · 2 mg/kg PO once monthly · PO · q30d
- Heartworm prophylaxis, control of adult hookworms, roundworms, and whipworms · 0.5 mg/kg PO once a month · PO · q30d · Minimum dosage. Can also be used with nitenpyram for flea control.
- Microfilaricide chemotherapy (in adulticide-pretreated dogs) · 0.5 mg/kg PO · PO · once · Repeat in 2 weeks if necessary. Give approximately one month after melarsomine.
- Treatment of generalized demodicosis · 1-3 mg/kg/day PO · PO · q24h · Until resolved · Begin at 1 mg/kg/day with skin scraping after 30 days. Increase to 2 mg/kg if minimal improvement, then 3 mg/kg if needed. Dogs homozygous for MDR1 mutation can show neuro side effects at 1-2.2 mg/kg/day.
- Treatment of cheyletiellosis · 2 mg/kg PO every 7 days for 3 doses · PO · q7d · 3 doses
- Treatment of scabies · 2 mg/kg PO every 7 days for 3 doses or 0.75 mg/kg once daily for 30 days · PO · q7d or q24h · 3 doses or 30 days
- Chronic rhinitis caused by Pneumonyssus caninum · 1 mg/kg PO once every 10 days for 3 treatments · PO · q10d · 3 treatments
- Nematodes · 0.5-1 mg/kg PO; repeat in 2 weeks · PO · once, repeat in 14 days · Until clear · If 14 days after second dose fecal is positive, a third dose is given. Appears to be safe in chelonians (unlike ivermectin).
給藥途徑
禁忌症
- Puppies less than 4 weeks of age or less than 2 lbs
- Kittens less than 6 weeks of age or less than 1.5 lbs
不良反應
- Transient shock-like syndrome (in microfilaremic animals)
- Ataxia
- Trembling
- Mydriasis
- Hypersalivation
- Lethargy
- Pyrexia
- Seizures
- Coma
藥物相互作用
- Benzodiazepines · Effects may be potentiated by milbemycin; concurrent use is not advised in humans and warrants caution in animals.
- P-glycoprotein inhibitors (Amiodarone, Ketoconazole, Cyclosporine, Diltiazem, Erythromycin, Clarithromycin, Quinidine, Spironolactone, Tamoxifen, Verapamil) · May inhibit the efflux pump at the blood-brain barrier, increasing the risk of milbemycin neurotoxicity, particularly in dogs at risk for the ABCB1-1 (MDR1) mutation.
監測
- Heartworm status (prior to initiation of therapy)
- Neurologic signs (especially in susceptible breeds or at high doses)
- Skin scrapings (if treating demodicosis)
過量
Beagles have tolerated a single oral dose of 200 mg/kg (200 times monthly rate). Rough-coated collies have tolerated doses of 10 mg/kg (20 times labeled) without adversity. Toxic doses can cause mydriasis, hypersalivation, lethargy, ataxia, pyrexia, seizures, coma, and death. There is no specific antidotal treatment; supportive therapy is recommended.
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