美拉索明
美拉索明（Melarsomine）是一種有機砷化學治療藥物，專門用於治療犬心絲蟲（*Dirofilaria immitis*）成蟲感染。它對成熟的成蟲和未成熟的（4個月大，L5階段）幼蟲具有高度療效。 **臨床要點**：雖然美拉索明是唯一獲准的成蟲殺滅劑，但目前美國心絲蟲協會（AHS）強烈建議採用多模式療法。建議在注射美拉索明前1至2個月，先使用大環內酯類藥物（如伊維菌素）和**多西環素（Doxycycline）**進行預處理。多西環素可消滅心絲蟲賴以生存和繁殖的共生菌（*Wolbachia*），從而削弱心絲蟲、減少蟲體生物量，並顯著降低蟲體死亡時引發的發炎反應及嚴重的肺血栓栓塞風險。 美拉索明比其前代藥物硫乙胂胺（thiacetarsamide）更安全且更有效，但其安全範圍仍然狹窄，需要精確的劑量和給藥技術。
作用機制: While the exact mechanism of action is not definitively established, as an arsenical compound, melarsomine is believed to exert its parasiticidal effect by binding to **sulfhydryl (-SH) groups** of essential enzymes within the parasite. * **Enzyme Inhibition** → Disrupts cellular respiration and vital metabolic pathways in the parasite. * **Target** → Highly effective (90-99%) at killing adult and L5 larval stages of *D. immitis* in dogs. * **Clearance** → Dead worms degrade and are swept into the pulmonary vasculature, where they are eventually cleared by the host's immune system (macrophages).
各物種劑量
- Heartworm disease (Class I & II) · 2.5 mg/kg deep IM as directed (lumbar epaxial muscles (L3-L5) twice 24 hours apart · IM · q24h for 2 doses · 2 days · Use alternating sides with each administration. In 4 months, the regimen may be repeated.
- Heartworm disease (Class III) · 2.5 mg/kg deep IM as directed (lumbar epaxial muscles (L3-L5). Strict rest and give all necessary systemic treatment. One month later, give 2.5 mg/kg deep IM as directed (lumbar epaxial muscles (L3-L5) twice 24 hours apart. · IM · Once, then q24h for 2 doses 1 month later · 1 month + 2 days · Requires strict rest.
- Heartworm disease (Alternative Protocol / AHS Treatment of Choice) · 2.5 mg/kg deep IM as directed (lumbar epaxial muscles; L3-L5). Strict rest and give all necessary systemic treatment. One month later, give 2.5 mg/kg deep IM as directed (lumbar epaxial muscles; L3-L5) twice 24 hours apart · IM · Once, then q24h for 2 doses 1 month later · 1 month + 2 days · Treatment of choice regardless of stage of disease due to increased safety and efficacy.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Class IV (very severe) heartworm disease / Caval syndrome
- Cats (reportedly very toxic)
- Intravenous (IV) administration
- Subcutaneous (SC) administration
不良反應
- Injection site reactions (pain, swelling, tenderness, firm nodules)
- Coughing/gagging
- Depression/lethargy
- Anorexia/inappetence
- Excessive salivation
- Fever
- Lung congestion
- Vomiting
- Pulmonary thromboembolism (can be fatal)
- Paresis and paralysis (rare)
藥物相互作用
- Aspirin · Has been shown not to reduce adverse effects and may complicate therapy; use is not recommended.
- CNS Depressant Drugs · Drugs that have similar adverse effects (e.g., depression) may cause additive adverse effects or increase their incidence when used with melarsomine.
監測
- Clinical efficacy
- Adverse effects (observe dogs for 24 hours after the last injection)
- Signs of pulmonary thromboembolism (coughing, hemoptysis, tachypnea, dyspnea)
- Injection site reactions
過量
There is a **low margin of safety** with melarsomine. * **3X dose (7.5 mg/kg)** in healthy dogs causes respiratory inflammation and distress, excessive salivation, restlessness, panting, vomiting, edema, tremors, lethargy, ataxia, cyanosis, stupor, and death. * **2X dose** in infected dogs has caused diarrhea, excessive salivation, restlessness, panting, vomiting, and fever. * **Treatment**: Dimercaprol (BAL in Oil) may be considered to treat melarsomine overdoses, though it may reduce the clinical efficacy of the melarsomine.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。