MOXIDECTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MOXIDECTIN (MOXIDECTIN).
Moxidectin is a macrocyclic lactone that binds to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, leading to increased chloride ion influx, hyperpolarization, and paralysis/death of susceptible parasites. It also potentiates gamma-aminobutyric acid (GABA)-gated chloride channels.
| Metabolism | Moxidectin is extensively metabolized in the liver primarily via CYP3A4 and to a lesser extent by other CYP enzymes. Metabolites include monohydroxylated and O-demethylated products. |
| Excretion | Primarily fecal (≈75% of total clearance) via biliary excretion of unchanged drug and metabolites; renal excretion accounts for <1% of the dose. |
| Half-life | Terminal elimination half-life is approximately 11–12 days in healthy adults; prolonged to 20–30 days in patients with hepatic impairment due to reduced clearance. |
| Protein binding | ≈85–89% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Vd ≈ 10–12 L/kg, indicating extensive tissue distribution (e.g., skin, fat, liver) with slow redistribution. |
| Bioavailability | Oral: approximately 85% (range 75–95%) with moderate interindividual variability; absorption is enhanced by fatty meal. |
| Onset of Action | Oral: Onset of antiparasitic effect occurs within 2–4 hours post-dose based on plasma levels exceeding therapeutic threshold for microfilarial reduction. |
| Duration of Action | Single oral dose provides sustained microfilarioidal activity for up to 12 months due to long half-life and slow elimination from tissues. |
Oral: 8 mg once daily for 1-2 days for onchocerciasis; 8 mg once for strongyloidiasis.
| Dosage form | TABLET |
| Renal impairment | No adjustment required for mild to moderate renal impairment; insufficient data for severe (GFR <30 mL/min) or ESRD. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B); no data for severe (Child-Pugh C). |
| Pediatric use | For onchocerciasis: 8 mg (one tablet) once for children weighing ≥15 kg and age ≥5 years; for strongyloidiasis: same dose. Weight <15 kg or age <5 years: not recommended. |
| Geriatric use | No specific dose adjustment; use caution due to potential age-related hepatic/renal decline and increased sensitivity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MOXIDECTIN (MOXIDECTIN).
| Breastfeeding | Moxidectin is excreted in human milk. M/P ratio not established. Potential for infant adverse effects. Avoid breastfeeding or discontinue drug. |
| Teratogenic Risk | Moxidectin is contraindicated in pregnancy. Animal studies show teratogenicity (malformations, embryotoxicity) at clinically relevant doses. No human data available. Avoid in all trimesters. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to moxidectin or any component of the formulation.","Co-infection with Loa loa (risk of severe neurological adverse reactions).","Severe hepatic impairment (Child-Pugh class C)."]
| Precautions | ["Use with caution in patients with hepatic impairment; avoid in severe hepatic impairment.","Not recommended for children under 12 years of age (safety not established).","May cause Mazzotti reaction (pruritus, rash, fever, lymphadenopathy) when treating onchocerciasis due to microfilariae death.","Potential for serious or fatal encephalopathy when treating Loa loa co-infection (not indicated for loiasis).","Avoid use during pregnancy unless benefit outweighs risk (pregnancy category C)."] |
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| Monitor for fetal exposure (ultrasound if inadvertent use). No specific maternal monitoring required beyond standard clinical care. |
| Fertility Effects | Animal studies show impaired fertility at high doses. Human data lacking. Reversible effects possible. |