左旋咪唑
左旋咪唑是一種咪唑並噻唑類衍生物，主要在大型動物中用作抗線蟲寄生蟲藥，過去也曾在小動物中用作殺微絲蟲藥和免疫刺激劑。 **臨床要點：** * **在小動物中使用的減少：** 由於其治療指數狹窄，加上更安全、更有效的驅蟲藥（如巨環內酯類、苯並咪唑類）的出現，左旋咪唑在現代犬貓臨床中已很少使用。 * **大型動物的應用：** 它在牛、羊和豬中仍是一種有價值的廣效驅蟲藥，對胃腸道和肺部線蟲特別有效，儘管寄生蟲抗藥性已成為日益嚴重的全球性問題。 * **免疫調節：** 其刺激細胞介導免疫的獨特能力，使其在標示外被用作慢性感染、免疫介導疾病和某些腫瘤的輔助療法，特別是在免疫功能低下的病患中。
作用機制: **Antiparasitic Action:** Levamisole acts as a cholinergic agonist at **nicotinic acetylcholine receptors** on the nematode muscle. * Receptor activation → continuous depolarization → **spastic paralysis** of the worm. * The paralyzed nematodes are subsequently expelled alive from the host's gastrointestinal or respiratory tract. * At higher concentrations, it interferes with nematode carbohydrate metabolism by blocking **fumarate reduction** and **succinate oxidation**. **Immunostimulant Action:** The exact mechanism is not fully elucidated. It is believed to: * Restore cell-mediated immune function in peripheral **T-lymphocytes**. * Stimulate phagocytosis and chemotaxis by **monocytes and macrophages**. * Effects are generally more pronounced in immunocompromised animals rather than healthy ones.
各物種劑量
- For removal of mature and immature Dictyocaulus vivapurus · 8 mg/kg PO · PO · Once
- For treatment of susceptible nematodes · 7.5 mg/kg PO · PO · Once
- For removal of mature and immature Dictyocaulus vivapurus · 8 mg/kg PO · PO · Once
- For treatment of susceptible nematodes · 7.5 mg/kg PO · PO · Once
- For the treatment of lungworms · 20-40 mg/kg PO every other day for 5-6 treatments · PO · q48h · 5-6 treatments
- For Aelurostrongylus abstrusus (lungworms) · 100 mg PO daily every other day for 5 treatments; give atropine (0.5 mg SC, 15 minutes before administering); or 15 mg/kg PO every other day for 3 treatments, then 3 days later: 30 mg/kg PO, then 2 days later: 60 mg/kg. · PO · Varies · Varies
- For Capillaria aerophilia (lungworms) · 4.4 mg/kg SC for 2 days, then 8.8 mg/kg once 2 weeks later; or 5 mg/kg PO once daily for 5 days, followed by 9 days of no therapy, repeat two times · SC/PO · Varies · Varies
- For the treatment of lungworms · 25 mg/kg every other day for 10-14 days · PO · q48h · 10-14 days
- For Capillaria aerophilia (lungworms) · 10 mg/kg PO once daily for 5 days; repeat in 9 days · PO · q24h · 5 days
給藥途徑
禁忌症
- Lactating dairy animals (not approved)
- Severely debilitated animals
- Patients with significant renal or hepatic impairment
- Cats with FIV or FIP (and likely ineffective in FeLV)
- Use as a dirofilarial adulticide
- Intravenous (IV) administration (never recommended)
- Intramuscular (IM) administration in birds (avoid if possible)
不良反應
- Cattle: Muzzle foaming, hypersalivation, excitement, trembling, lip-licking, head shaking, injection site swelling
- Sheep/Goats: Transient excitability, depression, hyperesthesia, salivation, stinging upon SC injection
- Swine: Salivation, muzzle foaming, coughing/vomiting (especially if infected with lungworms)
- Dogs: GI disturbances (vomiting, diarrhea), neurotoxicity (panting, shaking, agitation), immune-mediated anemia, agranulocytosis, dyspnea, pulmonary edema, immune-mediated skin eruptions (erythema multiforme, toxic epidermal necrolysis), lethargy
- Cats: Hypersalivation, excitement, mydriasis, vomiting
藥物相互作用
- Aspirin · Levamisole may increase salicylate levels
- Chloramphenicol · Fatalities have been reported after concomitant administration; avoid using these agents together
- Cholinesterase-inhibiting drugs (e.g., organophosphates, neostigmine) · Could theoretically enhance the toxic effects of levamisole; use together with caution
- Nicotine-like compounds (e.g., pyrantel, morantel, diethylcarbamazine) · Could theoretically enhance the toxic effects of levamisole; use together with caution
- Warfarin · Increased risk for bleeding
監測
- Clinical efficacy (fecal exams, resolution of clinical signs)
- Adverse effects/toxicity observation
過量
Signs of levamisole toxicity often mimic those of **organophosphate toxicity** due to its cholinergic effects. * **Clinical Signs:** Hypersalivation, hyperesthesias, irritability, clonic seizures, CNS depression, dyspnea, defecation, urination, and collapse. Acute overdosage can result in death due to respiratory failure. Cardiac arrhythmias may also be seen. * **Avian Toxicity:** In pet birds, 40 mg/kg SC is reported as a toxic dose. IM injections may cause more severe toxicity. Signs include depression, ataxia, leg/wing paralysis, mydriasis, regurgitation, and death. * **Treatment:** Primarily supportive, as animals generally recover within hours of dosing. If respiratory failure occurs, institute artificial ventilation with oxygen until recovery. For recent oral ingestion, emptying the gut and/or administering activated charcoal with cathartics may be indicated. * **Warning:** Intravenous (IV) administration is particularly hazardous and is never recommended.
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