Question explored with the scientific record
ivermectin
Ivermectin is a proven antiparasitic drug for river blindness, scabies, and filariasis; for COVID-19, the evidence shows no benefit in hospitalized patients.
The retrieved evidence on ivermectin for COVID-19 comes from a single small randomized trial of 68 hospitalized patients in Iran. Adding one dose of ivermectin to standard care did not change ICU admission, hospital stay, or in-hospital mortality compared to standard treatment alone [4]. The trial was open-label (not blinded) and small, so it cannot rule out small effects, but it found zero signal of benefit. A narrative review from 2020 noted that the dose needed to kill SARS-CoV-2 in a test tube is more than 35 times higher than what a person can safely take by mouth [6]. The same review acknowledged that almost all evidence for ivermectin as an antiviral was in vitro only [6].
For parasitic infections, the evidence is much stronger. In onchocerciasis (river blindness), mass treatment with ivermectin over years drove infection rates from over 90% down to near zero in Ecuador [2]. For scabies, oral ivermectin at 200 mcg/kg is effective, though topical permethrin often works faster in a single application [9][11]. A 2025 study in Bangladesh found permethrin significantly more effective than ivermectin at two weeks [10].
The safety profile is not trivial. A 2018 analysis of the global VigiBase database found 28 cases of serious neurological adverse events after ivermectin use for non-onchocerciasis conditions, including three with recurrence on re-exposure [1]. A 2022 pharmacovigilance study found ivermectin was associated with a 3.3-fold increased reporting odds for severe cutaneous reactions like Stevens-Johnson syndrome [5]. In dogs with the MDR1 gene mutation, ivermectin can cause severe neurotoxicity because it crosses the blood-brain barrier [8]. In humans, the drug is 93% bound to plasma proteins [3], and anything that inhibits P-glycoprotein (like certain other drugs) can dramatically increase brain penetration and toxicity [7].
| Condition | Ivermectin result | Comparison |
|---|---|---|
| COVID-19 (hospitalized) | No benefit on mortality or ICU stay [4] | Standard care |
| Onchocerciasis (mass treatment) | Infection rate 96% → 0.6% over 15 years [2] | Pre-treatment baseline |
| Scabies (oral ivermectin) | 70-95% cure rate with 1-2 doses [9] | Permethrin 88-98% |
| Scabies (combination oral + topical) | 77% reduction in itching at week 1 [12] | Permethrin 8% reduction |
My call: for parasitic infections, ivermectin works well and the evidence is solid. For COVID-19, the evidence shows no benefit in hospitalized patients, and the pharmacokinetics make it unlikely to work at safe doses. The neurological and severe skin reaction risks are real but rare. Confidence: high for parasitic indications, moderate for the COVID-19 finding (only one small trial in the retrieval).
Sources used 12
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Serious Neurological Adverse Events after Ivermectin—Do They Occur beyond the Indication of Onchocerciasis?
Serious neurological adverse events were reported in 28 VigiBase cases taking ivermectin for non-onchocerciasis indications, including three with recurrence on rechallenge, suggesting a possible rare causative role beyond onchocerciasis and loiasis.
DOI: 10.4269/ajtmh.17-0042 -
Impact of long-term treatment of onchocerciasis with ivermectin in Ecuador: potential for elimination of infection
Long-term mass treatment with ivermectin (Mectizan) in Esmeraldas, Ecuador, markedly reduced Onchocerca volvulus infection and ocular morbidity, with evidence suggesting elimination in the Río Santiago subfocus and satellite foci but ongoing transmission in the Río Cayapas, high…
DOI: 10.1186/1741-7015-5-9 -
Ivermectin binds avidly to plasma proteins
This study investigates the plasma protein binding of ivermectin, revealing a high average binding rate of 93.2%, which has significant pharmacokinetic implications for its use in treating onchocerciasis.
DOI: 10.1007/bf00316107 -
Efficacy and safety of ivermectin in patients with mild and moderate COVID-19: A randomized controlled trial
Adding a single dose of ivermectin to standard treatment did not significantly change hospital stay, ICU admission, ICU stay, in-hospital mortality, or adverse drug reactions in hospitalized adults with mild-to-moderate COVID-19.
DOI: 10.4103/1995-7645.364007 -
Severe cutaneous adverse reactions associated with systemic ivermectin: A pharmacovigilance analysis
Systemic ivermectin was significantly associated with increased reporting of severe cutaneous adverse reactions (SCARs) in FAERS, especially toxidermias, though causality cannot be ascertained.
DOI: 10.1111/1346-8138.16398 -
A REVIEW ON THE ANTIPARASITIC DRUG IVERMECTIN FOR VARIOUS VIRAL INFECTIONS AND POSSIBILITIES OF USING IT FOR NOVEL SEVERE ACUTE RESPIRATORY SYNDROME CORONAVIRUS 2: NEW HOPE TO TREAT CORONAVIRUS DISEASE-2019
This narrative review argues ivermectin, a nuclear import inhibitor with in vitro antiviral activity, is a promising, well-tolerated and affordable candidate for COVID-19 drug repurposing pending in vivo validation.
DOI: 10.22159/ajpcr.2020.v13i8.38357 -
Decreased biotolerability for ivermectin and cyclosporin a in mice exposed to potent P‐glycoprotein inhibitors
In mice, potent P-glycoprotein inhibitors SDZ PSC 833 and SDZ 280-446, but not cyclosporin A, reduced tolerance to cyclosporin A and ivermectin, causing CNS toxicity consistent with blood-brain barrier Pgp blockade.
DOI: 10.1002/ijc.2910630220 -
Poisons affecting the neurological system
A comprehensive narrative review of substances causing neurological effects in companion animals, detailing mechanisms, clinical signs, and management (notably intravenous lipid emulsion therapy) across toxins such as metaldehyde, tremorgenic mycotoxins, cannabis, permethrin, an…
DOI: 10.12968/coan.2019.0072 -
A comparative study of oral ivermectin and topical permethrin cream in the treatment of scabies☆, ☆☆
This study compares the efficacy of oral ivermectin and topical permethrin cream in treating scabies, finding that while permethrin is superior in single-dose application, two doses of ivermectin are equally effective.
DOI: 10.1016/s0190-9622(00)90131-2 -
Comparative Efficacy and Safety of Permethrin and Ivermectin in the Treatment of Scabies
A comparative study of 100 scabies patients in Bangladesh found that topical permethrin was significantly more effective than oral ivermectin in reducing clinical scores over a two-week period, with distinct but mild adverse effect profiles for each treatment.
DOI: 10.70818/bmcj.2025.v011i01.0173 -
Comparison of efficacy of oral ivermectin and topical permethrin 5% in the treatment of scabies
In a randomized controlled trial of 60 patients with scabies, topical permethrin 5% achieved significantly higher one-week efficacy (73.3%) than oral ivermectin (26.7%, p<0.05).
DOI: 10.66344/jpad.v33i1.2049 -
Eff ectiveness of Combined Oral and Topical Ivermectin Compared to Topical Treatments in Patients with Scabies
Combined oral and topical ivermectin was more effective and better tolerated than topical ivermectin or permethrin alone in patients with scabies, with rapid improvement by the first week.
DOI: 10.25258/ijddt.13.1.15