ドラメクチン
ドラメクチンは、アベルメクチン系抗寄生虫薬に属する**マクロライド系**の薬剤です。 - **産業動物への使用**: 牛および豚の消化管内線虫、肺虫、眼虫、ウシバエ幼虫、シラミ、ヒゼンダニの治療薬として、注射剤および外用ポアオン剤がFDAに承認されています。 - **伴侶動物への使用**: 犬および猫において、主に**全身性毛包虫症（ニキビダニ症）**や犬回虫症の治療に適用外使用（適応外処方）されます。 > **臨床上のポイント**: 非常に有効ですが、小動物への使用は完全に適用外であり、特にMDR1（ABCB1）遺伝子変異を持つ牧羊犬種では重篤な神経毒性のリスクを伴います。
作用機序: Doramectin exerts its antiparasitic effect by binding to **glutamate-gated chloride channels** found in invertebrate nerve and muscle cells. - **Mechanism**: Binding → increases membrane permeability to chloride ions → cellular hyperpolarization → **flaccid paralysis and death** of the parasite. - It also enhances the release of **gamma-aminobutyric acid (GABA)** at presynaptic neurons, further inhibiting nerve transmission. - **Mammalian Safety**: Mammals lack glutamate-gated chloride channels, and avermectins typically do not cross the intact mammalian blood-brain barrier (where GABA receptors reside) due to the **P-glycoprotein efflux pump**. Toxicity occurs when this pump is deficient (e.g., MDR1 mutation) or overwhelmed by massive overdoses.
動物種別の用量
- Feline demodicosis (D. cati, D. gatoi) · 600 micrograms/kg (0.6 mg/kg) · SC · once per week · Extra-label. Get informed consent from owner. Alternative treatments include Lime sulfur dips or amitraz.
- Labeled indications (Injectable) · 200 micrograms/kg (1 mL per 110 lb. body weight) · SC/IM · once · Beef Quality Assurance guidelines recommend SC administration as the preferred route.
- Labeled indications (Pour-on) · 500 micrograms/kg (1 mL per 22 lb. body weight) · topical · once · Administer topically along the mid-line of the back in a narrow strip between the withers and tailhead.
- Labeled indications · 300 micrograms/kg (1 mL per 75 lb. body weight) · IM · once · Intramuscular injections should be administered into the muscular region of the neck.
- P. cuniculi infestations (Rabbits) · 200 micrograms/kg · IM · once · once
- Treatment of generalized demodicosis · 600 micrograms/kg · PO · once daily · Until 60 days without improvement · Extra-label. If improvement is not seen after 60 days, an alternative therapy should be used.
- Treatment of generalized demodicosis · 600 micrograms/kg (0.6 mg/kg) · SC · once per week · Extra-label. Get informed consent from owner.
投与経路
禁忌
- Dogs with MDR1-allele mutations (relative/absolute depending on dose)
- Female dairy cattle 20 months of age or older
- Calves to be processed for veal
有害事象
- Injection site blemishes (IM administration)
- Pupil dilation (mydriasis) in dogs
- Lethargy
- Blindness
- Coma (especially in MDR1-mutant dogs)
モニタリング
- Clinical efficacy (resolution of parasites/lesions)
- Signs of neurotoxicity in off-label species (dogs/cats)
過量投与
In field trials, no toxic signs were seen in cattle given up to 25X the recommended dose. In breeding animals (bulls, and cows in early and late pregnancy), a dose 3 times the recommended dose had no effect on breeding performance.
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。