Antiparasitic Pregnancy: Should only be used when strictly indicated. Limited human data (~300 first-trimester exposures) indicated no adverse effects; animal studies show reproductive toxicity. Delay treatment of nursing mothers until 1 week after birth.

Ivermectin

Brand names: Stromectol, Soolantra (topical)

Ivermectin is an antiparasitic agent used for onchocerciasis, strongyloidiasis and other helminthic and ectoparasitic infections, available in oral and topical formulations.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 200 micrograms/kg as a single oral dose (gastrointestinal strongyloidiasis and human sarcoptic scabies)

Route: Oral — on an empty stomach with water (no food for 2 hours before or after)

Frequency: Single dose

Weight-banded dosing with 3 mg tablets for strongyloidiasis/scabies (200 micrograms/kg): 15-24 kg = 1 tablet; 25-35 kg = 2; 36-50 kg = 3; 51-65 kg = 4; 66-79 kg = 5; >=80 kg = 6 tablets. Wuchereria bancrofti microfilaraemia (mass distribution): single dose once every 6 months providing ~150-200 micrograms/kg, or where treatment is only every 12 months 300-400 micrograms/kg (3 mg tablets: 15-25 kg = 1 tablet 6-monthly / 2 tablets 12-monthly; 26-44 kg = 2/4; 45-64 kg = 3/6; 65-84 kg = 4/8). Scabies: assess cure at 4 weeks; a second dose within 2 weeks only if new lesions appear or parasitology is positive; profuse/crusted scabies may need a second dose within 8-15 days and/or concomitant topical therapy. Safety not established in patients weighing under 15 kg. Efficacy in immunocompromised strongyloidiasis patients not established (single dose may be insufficient).

Paediatric dose

Dose: 200 micrograms/kg

Route: Oral (single dose, empty stomach with water)

Frequency: Single dose

200 micrograms/kg single oral dose for strongyloidiasis and scabies, using the same weight-banded tablet counts as adults. Safety has not been established in children weighing under 15 kg. Children under 6 years of age (and at least 15 kg): tablets should be crushed before swallowing.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Nausea and vomiting
Diarrhoea, constipation, abdominal pain, anorexia
Dizziness, somnolence, vertigo, tremor
Pruritus, rash, urticaria (Mazzotti-type reactions in onchocerciasis)
Rare but serious: Stevens-Johnson syndrome / toxic epidermal necrolysis; neurological toxicity and encephalopathy (especially with heavy Loa loa co-infection)

Interactions

Diethylcarbamazine citrate (DEC) — concomitant use not recommended in mass chemotherapy campaigns for Wuchereria bancrofti filariasis in Africa (risk of serious reactions where Loa loa co-infection is present)
Warfarin — rare post-marketing reports of increased INR (International Normalized Ratio) (US labelling)

Clinical monograph

How it works

It binds glutamate-gated chloride channels in invertebrate nerve and muscle cells, increasing chloride permeability and causing parasite paralysis and death.

Prescribing in practice

In areas co-endemic for Loa loa, treatment can precipitate serious or fatal encephalopathy in patients with high microfilarial loads, so screen before treating.
Onchocerciasis usually requires repeated dosing because the drug kills microfilariae but not adult worms.
The mammalian central nervous system is normally protected by the blood-brain barrier, but caution applies in conditions that may compromise it.

Monitoring

No routine laboratory monitoring is required; observe for Mazzotti-type reactions when treating microfilarial infections.

Counselling the patient

Itching, rash, swollen glands or joint aches can occur after treatment as parasites die.
Further doses may be needed to fully clear the infection.
Take oral ivermectin as directed and return for any planned repeat treatment.

Evidence & guidelines

Widely used in mass drug administration programmes for onchocerciasis; refer to the SPC and WHO guidance for indication-specific use.

Reference: NICE CKS; WHO; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways