ミルベマイシンオキシム
ミルベマイシンオキシムは、獣医療で広く使用されている**マクロライド系抗寄生虫薬**です。 - **主な用途**：毎月の犬糸状虫（フィラリア）予防および腸内寄生虫（鉤虫、回虫、鞭虫）の駆除。 - **適応外使用**：全身性毛包虫症、疥癬、ツメダニ症、鼻ダニの治療。 > **臨床のポイント**：一般的に安全ですが、**ABCB1（MDR1）遺伝子変異**を持つ犬種（コリー、オーストラリアン・シェパード、シェルティなど）に対して毛包虫症治療のために高用量を連日投与する場合は、神経毒性のリスクが高まるため注意が必要です。これらの犬種にとってはイベルメクチンよりも安全な代替薬と見なされることが多いですが、高用量治療を開始する前には遺伝子検査が推奨されます。
作用機序: 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.
動物種別の用量
- 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).
投与経路
禁忌
- 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
有害事象
- Transient shock-like syndrome (in microfilaremic animals)
- Ataxia
- Trembling
- Mydriasis
- Hypersalivation
- Lethargy
- Pyrexia
- Seizures
- Coma
薬物相互作用
- 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.
モニタリング
- Heartworm status (prior to initiation of therapy)
- Neurologic signs (especially in susceptible breeds or at high doses)
- Skin scrapings (if treating demodicosis)
過量投与
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.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。