Ivermectin is an antiparasitic tablet used against onchocerciasis (river blindness), strongyloidiasis and infestations with lice and scabies mites. It paralyses the parasites, which are then cleared by the body.
Also known as: Stromectol
Clarithromycin may increase ivermectin plasma levels through CYP3A4 inhibition, potentially worsening neurological side effects.
Ivermectin is metabolised by CYP3A4; clarithromycin is a moderate inhibitor of this pathway.
Neurological status during the first 24–48 h after co-administration.
Excessive drowsiness, incoordination, low blood pressure.
Avoid the combination when possible; if unavoidable, monitor for drowsiness, ataxia or hypotension after dosing.
DailyMed — Stromectol (ivermectin) Tablet [Merck] label, Drug Interactions: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=681888c9-af79-4b7d-ae80-c3f4f6f1effd
Ivermectin bioavailability increases about 2.5-fold when taken with a meal.
Take with a meal to maximise absorption (single or weight-based dose).
DailyMed — Stromectol (ivermectin): "administer with food"; EMC-UK ivermectin SmPC 4.2.
Safety data in pregnancy are limited — do not use unless disease risk justifies it.
Defer treatment in pregnant women; contraception during treatment.
Prontuário/WHO (ivermectin — fetal safety not established); EMC-UK ivermectin SmPC 4.6.
Hepatic metabolism reduces clearance — caution in liver disease.
Assess liver function with repeated courses.
EMC-UK — ivermectin SmPC 4.4 (hepatic impairment).
Ivermectin should only be used with great caution when the blood–brain barrier may be compromised (meningitis, trypanosomiasis) — risk of CNS depression.
Confirm absence of active CNS disease before high doses.
Prontuário Terapêutico INFARMED, 1.4 (ivermectin — compromised BBB).
No entry in the Prontuário Annex 1. Published mass-treatment data (WHO/African studies) showed no increase in malformations with 1st-trimester exposure, but labels (EMC/Stromectol) recommend avoidance in pregnancy, especially the 1st trimester — the risk of untreated onchocerciasis/filariasis is also weighed.
Avoid, especially in the 1st trimester; use if benefit (severe filarial disease) justifies.
Excretion into milk is not well characterised; avoid breastfeeding during treatment and for ~1 week after (long metabolite half-life) as a precaution.
Avoid pregnancy during and for 1 month after treatment (EMC-UK).
EMC-UK (MHRA) — Ivermectin SmPC (Stromectol): https://www.medicines.org.uk/emc/product/2917/smpc (section 4.6). WHO Mectizan donation programme data (observational).
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Systemic antiparasitic targeted at nematodes (onchocerciasis, strongyloidiasis) and arthropods (scabies, lice); microfilariae death triggers inflammatory (Mazzotti) reactions proportional to parasite load.
Binds with high affinity to glutamate-gated chloride channels in invertebrate nerve/muscle cells, opening them and causing hyperpolarisation, flaccid paralysis and death by starvation/phagocytosis. In mammals the homologous channels are confined to the CNS and P-glycoprotein excludes the drug (blood-brain barrier) — the basis of selective safety.
Oral bioavailability ~65% (up to 2.5-fold increase with food); peak 4–5 h; high lipophilia, volume of distribution ~3.1 L/kg, concentrated in adipose tissue and liver; does not significantly cross the BBB.
Hepatic hydroxylation and demethylation (mainly CYP3A4) to inactive metabolites; P-gp substrate. Potent inducers (rifampicin, antiepileptics) reduce exposure; CYP3A4/P-gp inhibitors raise it.
~18 h (range 12–54 h); faecal excretion predominates (> 90% of metabolites), < 1% unchanged in urine.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
