Drug reference

Ivermectin

Anthelmintic · Antiparasitic

START

Confirm parasitic infection (stool microscopy, skin snip, serology). Weigh patient accurately (dosing is weight-based). Rule out pregnancy. Screen for Loa loa co-infection if from endemic area (risk of encephalopathy).

TYPICAL MAX

200 mcg/kg single dose. Do not exceed for standard indications.

STOP IF

Signs of encephalopathy (confusion, seizures, severe headache), severe hypersensitivity, pregnancy

WATCH

Mazzotti reaction symptoms (pruritus, rash, fever, arthralgia — in onchocerciasis), Loa loa microfilarial load if co-infection suspected, neurological symptoms

CDSCO approvedSchedule HJan AushadhiATC P03AC01

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1.1h · absorption onset
PEAK: 4.5h · 4-5 h (first peak); 6-12 h (enterohepatic)
t½: 18h · ~18 h (plasma); 2-3 days (terminal, tissue)
DURATION: 12.9w · Months (tissue reservoir)

EXCRETION

~98% fecal (metabolites); <1% renal; CYP3A4 metabolism

route + CYP

INTERACTIONS

1 major

SEVERE in our sources

PREGNANCY

FDA PLLR: Safety not established. Animal studies showed teratogenicity at doses toxic to the mother. Avoid in pregnancy unless benefit clearly outweighs risk. Weight >15 kg for pediatric dosing.

FDA category + note

Top interactionssee all 9 →

DiethylcarbamazineSevereDatabaseKimi deep-research + Cla · p1822, p1824

Available in India

254 branded formulations and 468 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Ivermectin is a macrocyclic lactone derivative of avermectin B1 that acts as a positive allosteric modulator of glutamate-gated chloride channels (GluCl) in invertebrate nerve and muscle cells. It binds selectively and with high affinity to these channels, increasing chloride ion conductance, causing hyperpolarization of neuronal and muscular membranes, and resulting in flaccid paralysis and death of the parasite. It may also interact with gamma-aminobutyric acid (GABA)-gated chloride channels in nematodes. The selective toxicity is due to the absence of glutamate-gated chloride channels in mammals and the low affinity of ivermectin for mammalian ligand-gated chloride channels. Ivermectin does not readily cross the blood-brain barrier in humans (except in conditions with compromised blood-brain barrier).

Indications

Onchocerciasis (river blindness) — Onchocerca volvulus microfilariaeStrongyloidiasis (Strongyloides stercoralis) — intestinal and disseminatedLymphatic filariasis (Wuchereria bancrofti, Brugia malayi) — mass drug administrationScabies (Sarcoptes scabiei) — especially crusted scabiesHead lice (Pediculus humanus capitis)Ascariasis (Ascaris lumbricoides) — off-labelTrichuriasis (Trichuris trichiura) — off-labelLoiasis (Loa loa) — with caution (risk of encephalopathy in high microfilarial loads)

Dosing

Adult: Strongyloidiasis: 200 mcg/kg PO single dose; repeat if immunocompromised or persistent infection. Onchocerciasis: 150 mcg/kg PO single dose; repeat every 6-12 months. Scabies: 200 mcg/kg PO single dose (repeat at 7-14 days for crusted scabies). Filariasis (MDA): 150-200 mcg/kg + albendazole 400 mg PO annually.
Pediatric: ≥15 kg: same as adult weight-based dosing. <15 kg: not recommended (safety not established). Head lice (≥6 months): 200 mcg/kg PO single dose.
Renal adjustment: No adjustment required.
Hepatic adjustment: No adjustment required; minimal hepatic metabolism.
Geriatric: No specific adjustment.
Max dose: 200 mcg/kg/dose; single dose for most indications

Pharmacokinetics

Onset

Microfilaricidal effect: within 48 hours. Scabies: mite death within 1-2 days.

Peak effect

Oral: peak plasma at 4-5 hours; second peak at 6-12 hours (enterohepatic recycling).

Duration

Long tissue half-life in adipose tissue; antiparasitic effect persists months for onchocerciasis.

Half-life

~18 hours (plasma); terminal half-life 2-3 days due to extensive tissue distribution (adipose tissue, skin).

Bioavailability

~60% (oral on empty stomach; increased with food/fat).

Protein binding

~93% (bound primarily to plasma albumin).

Metabolism

Hepatic via CYP3A4 (primary) and CYP1A2. Extensively metabolized to at least 10 metabolites (demethylated, hydroxylated). Less than 1% excreted unchanged.

Excretion

Feces: ~98% (as metabolites). Urine: <1% (unchanged and metabolites).

Contraindications

Hypersensitivity to ivermectin or any component
Pregnancy (safety not established; avoid unless benefit clearly outweighs risk)
Breastfeeding (excreted in milk; avoid or suspend breastfeeding for 24 hours after dose)
Loiasis with high Loa loa microfilarial load (>30,000/mL) — risk of encephalopathy/meningoencephalitis

Side effects

Common

Mazzotti reaction (in onchocerciasis): pruritus, rash, edema, arthralgia, fever, lymphadenopathy — due to dying microfilariaeFatigueDizzinessNausea, diarrheaAbdominal pain

Serious

Neurotoxicity/encephalopathy (especially with high Loa loa microfilarial loads or compromised blood-brain barrier)
Severe hypersensitivity (anaphylaxis, angioedema)
Hepatotoxicity (rare)
Severe Mazzotti reaction (prostration, hypotension, high fever — requires corticosteroid management)
Retinal toxicity (rare, with prolonged use)
Teratogenicity concern (animal studies showed embryotoxicity at high doses)

Pregnancy & lactation

Pregnancy

FDA PLLR: Safety not established. Animal studies showed teratogenicity at doses toxic to the mother. Avoid in pregnancy unless benefit clearly outweighs risk. Weight >15 kg for pediatric dosing.

Lactation

Excreted in breast milk in low concentrations. Theoretical risk to nursing infant. AAP recommends suspending breastfeeding for 24 hours after single dose (pump and discard milk).

Drug interactions

Diethylcarbamazine

Severe

Database

Concurrent use with ivermectin in patients with high Loa loa microfilarial loads dramatically increases risk of fatal encephalopathy/meningoencephalitis. Both are microfilaricidal.

Do NOT co-administer ivermectin and DEC in Loa loa-endemic areas without first assessing Loa loa microfilarial load. If Loa loa load >30,000/mL, avoid both drugs or pretreat with albendazole to reduce load.

Source: Kimi deep-research + Cla · p1822, p1824

Levamisole

Moderate

Textbook

Increased plasma levels of ivermectin.

Source: G&G 14e · p1325-1334

Clarithromycin

Moderate

Database

Increased ivermectin plasma concentrations, potentially leading to increased adverse effects (e.g., neurological toxicity).

Monitor for increased ivermectin side effects. Consider dose reduction of ivermectin if co-administration is necessary.

Source: DDInter

Albendazole

Moderate

Database

Standard combination for lymphatic filariasis mass drug administration (MDA). No direct pharmacokinetic interaction of concern, but additive adverse effects (hepatotoxicity, GI upset) may occur.

Standard MDA regimen (ivermectin 150-200 mcg/kg + albendazole 400 mg annually). Monitor LFTs and adverse effects.

Source: Kimi deep-research + Cla

Cyp3a4 Inducers

Moderate

Database

CYP3A4 inducers increase ivermectin metabolism, reducing plasma levels and potentially causing treatment failure for parasitic infections.

Monitor for treatment failure (persistent parasites). May need higher ivermectin dose or repeat dosing. Consider alternative antiparasitic if concurrent CYP3A4 inducer cannot be stopped.

Source: Kimi deep-research + Cla

Cyp3a4 Inhibitors

Moderate

Database

CYP3A4 inhibitors reduce ivermectin metabolism, increasing plasma levels and risk of neurotoxicity (especially in patients with conditions that compromise the blood-brain barrier).

Monitor for CNS side effects (dizziness, ataxia, confusion). Use caution in patients with meningitis or other CNS conditions.

Source: Kimi deep-research + Cla

Ketoconazole

Moderate

Database

Increased ivermectin plasma concentrations, potentially leading to increased adverse effects (e.g., neurological toxicity).

Monitor for increased ivermectin side effects. Consider dose reduction of ivermectin if co-administration is necessary.

Source: DDInter

Ritonavir

Moderate

Database

Increased ivermectin plasma concentrations, potentially leading to increased adverse effects (e.g., neurological toxicity).

Monitor for increased ivermectin side effects. Consider dose reduction of ivermectin if co-administration is necessary.

Source: DDInter

Warfarin

Moderate

Database

Ivermectin may enhance the anticoagulant effect of warfarin by an unknown mechanism (possibly altering vitamin K metabolism or displacing warfarin from protein binding).

Monitor INR closely when starting or stopping ivermectin in patients on warfarin. Anticipate dose adjustment.

Source: Kimi deep-research + Cla

3 additional unreviewed or low-confidence interactions hidden because their provenance or source detail is insufficient.