Ivermectin Drug Interactions: What to Avoid and What to Tell Your Doctor

Ivermectin has a manageable drug interaction profile, but there are several combinations that require attention — particularly for patients on blood thinners or certain HIV, antifungal, or cardiac medications. Understanding these interactions can help you have an informed conversation with your doctor before taking ivermectin.

The Most Important Interaction: Warfarin and Blood Thinners

The most clinically significant interaction with ivermectin is with warfarin (Coumadin, Jantoven). Taking ivermectin can substantially increase warfarin's anticoagulant effect — meaning your blood becomes much thinner than intended — raising the risk of dangerous bleeding.

If you take warfarin and need ivermectin, your doctor will typically:

• Inform your anticoagulation clinic or prescribing provider
• Schedule an INR (blood clotting) test within a few days after taking ivermectin
• Possibly adjust your warfarin dose based on the result

Do not skip this monitoring step if you're a warfarin user. The interaction can be serious even with a single dose of ivermectin.

P-glycoprotein Inhibitors: The CNS Risk Group

Many of ivermectin's most important interactions involve drugs that affect P-glycoprotein (P-gp) — a transport protein that pumps ivermectin out of the brain. If P-gp is inhibited, ivermectin can accumulate in the central nervous system and cause neurological toxicity: confusion, dizziness, ataxia, and in severe cases, seizures or coma.

Drugs that inhibit P-glycoprotein and should be used with caution alongside ivermectin include:

• Quinidine (a heart rhythm medication): Significant P-gp inhibitor — avoid combination or use extreme caution
• Ritonavir and other HIV protease inhibitors (atazanavir, lopinavir): Can increase ivermectin blood levels; monitor closely
• Itraconazole (antifungal): Inhibits P-gp and CYP3A4, increasing ivermectin exposure
• Erythromycin (antibiotic): P-gp inhibitor; use with caution
• Verapamil and other calcium channel blockers: Some also affect P-gp; discuss with your doctor

P-glycoprotein Inducers: Reduced Effectiveness

Some drugs increase P-glycoprotein activity, which can actually reduce the effectiveness of ivermectin by pumping more of it out of the body faster:

• Rifampin (antibiotic used for tuberculosis): A potent P-gp inducer that can significantly decrease ivermectin blood levels and potentially reduce its antiparasitic efficacy

Alcohol: Increase in Side Effects

Drinking alcohol while taking ivermectin can increase the risk and severity of side effects — particularly dizziness, drowsiness, and low blood pressure. There's no defined safe threshold. The safest approach is to avoid alcohol on the day you take ivermectin and for at least 24 hours afterward.

The Azithromycin-Ivermectin Interaction

When ivermectin is co-administered with albendazole and azithromycin (a combination used in mass drug administration programs for lymphatic filariasis), studies show that azithromycin increases ivermectin's peak blood levels by approximately 27% and overall exposure (AUC) by 31%. While this combination is used intentionally in some global health programs, patients taking azithromycin for other infections should mention this to their provider before taking ivermectin.

Food Interactions

Food significantly affects how much ivermectin your body absorbs. Taking ivermectin with a high-fat meal can increase absorption by up to 2.5-fold compared to taking it on an empty stomach. This is why the prescribing instructions specifically say to take ivermectin on an empty stomach with a full glass of water.

Taking it with food isn't automatically dangerous, but it means you're getting significantly more drug than your prescribed dose was calibrated for — which can increase side effect risk.

What to Tell Your Doctor Before Taking Ivermectin

Share this complete list with your prescriber:

• All prescription medications, including blood thinners, HIV medications, antifungals, antibiotics, and cardiac drugs
• All OTC medications, supplements, and herbal products
• Any travel to West or Central Africa (important for Loa loa co-infection risk assessment)
• Pregnancy or breastfeeding status
• Any liver disease or impaired liver function

For a comprehensive guide to ivermectin's side effects and safety profile, see our article on ivermectin side effects.