Ivermectin is an antiparasitic medication prescribed to treat infections caused by specific parasites [1.6.4]. In tablet form, it is FDA-approved for human use to combat intestinal strongyloidiasis (a type of roundworm infection) and onchocerciasis, also known as river blindness [1.6.1, 1.6.6]. Topical versions are used for conditions like rosacea and head lice [1.6.4]. It works by paralyzing and killing the parasites [1.6.4].
It is critical to use ivermectin only as prescribed by a licensed healthcare provider. The FDA has not authorized or approved ivermectin for treating or preventing viral illnesses, including COVID-19 [1.6.1, 1.6.2]. Taking large, unprescribed doses or using formulations intended for animals can be dangerous and lead to serious harm, including overdose symptoms like seizures, coma, and even death [1.6.1]. To ensure your safety, understanding potential interactions and contraindications is paramount.
Key Medications to Avoid or Use with Caution
Ivermectin can interact with numerous other drugs, which can alter its effectiveness or increase the risk of side effects [1.2.1]. Ivermectin is primarily metabolized by the CYP3A4 enzyme in the liver and is also a substrate of the P-glycoprotein (P-gp) efflux transporter [1.2.3, 1.2.5]. Consequently, drugs that inhibit or induce this enzyme or transporter can significantly affect ivermectin's concentration in the body.
Drugs with Major Interactions
- Warfarin (and other anticoagulants): Taking ivermectin with blood thinners like warfarin can enhance the anticoagulant effect, leading to an increased risk of unusual or prolonged bleeding [1.2.2, 1.2.7, 1.7.1]. Your doctor may need to monitor your INR (International Normalized Ratio) more closely if you take these medications together [1.2.7].
- Sedatives and Anti-Anxiety Medicines: Drugs that depress the central nervous system, such as lorazepam (Ativan), clonazepam (Klonopin), and phenobarbital, may have additive effects when taken with ivermectin, potentially increasing drowsiness or other side effects [1.2.1].
- P-gp Substrates with a Narrow Therapeutic Index: Some medications should be avoided or require dose adjustments because of significant P-gp interactions. These include quinidine, lasmiditan, and erdafitinib [1.2.5].
Drugs that Increase Ivermectin Levels
Certain medications inhibit the CYP3A4 enzyme or P-gp transporter, causing ivermectin to build up in the body and increasing the risk of side effects [1.2.2].
- Antifungals: Ketoconazole, itraconazole, and posaconazole can slow the breakdown of ivermectin [1.2.2, 1.4.5].
- Antibiotics: Macrolide antibiotics like clarithromycin and erythromycin can increase ivermectin levels [1.2.4].
- Antiviral Agents: HIV protease inhibitors like ritonavir and indinavir can decrease the metabolism of ivermectin [1.2.4, 1.2.5].
- Other Medications: Amiodarone, verapamil, cyclosporine, and diltiazem are other examples of drugs that can increase ivermectin concentrations [1.2.4].
Drugs that Decrease Ivermectin Levels
Conversely, some substances induce the CYP3A4 enzyme, which can speed up the metabolism of ivermectin, potentially making it less effective.
- Herbal Supplements: St. John's Wort is a well-known inducer that can decrease ivermectin levels [1.2.5].
- Anticonvulsants: Carbamazepine, phenytoin, and fosphenytoin can increase ivermectin metabolism [1.2.4, 1.2.5].
- Antibiotics: Rifampin can significantly lower the concentration of ivermectin in the blood [1.2.5].
Ivermectin Drug Interaction Comparison Table
| Drug/Drug Class | Example(s) | Potential Interaction with Ivermectin | Management Recommendation |
|---|---|---|---|
| Anticoagulants | Warfarin, Acenocoumarol | Can increase the blood-thinning effect, raising the risk of bleeding [1.2.2, 1.2.6]. | Use with caution; requires close monitoring by a healthcare provider [1.2.7]. |
| CYP3A4/P-gp Inhibitors | Ketoconazole, Itraconazole, Clarithromycin, Ritonavir | Can increase ivermectin concentration and risk of side effects [1.2.2, 1.2.5]. | Use with caution; monitor for adverse effects. Dose adjustments may be needed [1.2.5]. |
| CYP3A4/P-gp Inducers | St. John's Wort, Carbamazepine, Rifampin | Can decrease ivermectin concentration, reducing its effectiveness [1.2.5]. | Use with caution; monitor for lack of efficacy [1.2.5]. |
| Sedatives/Anti-Anxiety | Lorazepam, Phenobarbital | Can potentially increase central nervous system side effects like drowsiness and dizziness [1.2.1]. | Use with caution and discuss with your doctor [1.2.1]. |
Substances and Supplements: What to Be Aware Of
Alcohol
While there are no formally recognized direct interactions between ivermectin and alcohol, it is generally recommended to avoid or limit alcohol consumption during treatment [1.7.1]. Drinking alcohol may worsen common side effects of ivermectin, such as dizziness, sleepiness, nausea, and vomiting [1.7.1, 1.7.5]. Some reports suggest alcohol may increase the plasma concentrations of ivermectin, potentially leading to undue adverse effects [1.7.6].
Food
Healthcare providers generally recommend taking ivermectin tablets on an empty stomach with a full glass of water [1.3.3, 1.3.5, 1.3.6]. This typically means taking it at least 1 hour before or 2 hours after a meal [1.3.7]. While one study found the effect of a high-fat meal to be minimal [1.3.4], the standard advice is to take it without food to ensure proper absorption unless directed otherwise by your doctor [1.3.2].
Herbal Supplements and Vitamins
There are few specific reports on interactions between ivermectin and most vitamins or herbs [1.8.3]. However, this does not mean interactions are not possible. St. John's Wort is known to decrease ivermectin levels and should be used with caution [1.2.5]. Echinacea may also alter blood levels of ivermectin [1.8.1]. It is crucial to tell your doctor about all prescription drugs, over-the-counter medicines, vitamins, and herbal supplements you are taking [1.8.2].
Pre-existing Health Conditions and Contraindications
Certain individuals should not take ivermectin or should use it with extreme caution under medical supervision.
- Hypersensitivity: Anyone with a known allergy to ivermectin or any of its ingredients should not take the medication [1.4.3, 1.4.5].
- Liver Problems: Since ivermectin is processed by the liver, people with existing liver disease may be at higher risk for side effects, and the drug could worsen their condition [1.2.1, 1.4.5].
- Asthma: Ivermectin may worsen asthma, although this was reported after the drug was on the market rather than in initial studies [1.4.5].
- Seizure Disorders: As ivermectin has been reported to cause seizures in some people, those with a history of seizures should discuss the risks with their doctor [1.2.1, 1.4.5].
- Weakened Immune System: For individuals with conditions that weaken the immune system, such as HIV, ivermectin may not be as effective, and multiple doses might be required [1.2.1, 1.4.5].
- Pregnancy and Breastfeeding: Ivermectin is generally not recommended during pregnancy as animal studies suggest potential harm, though human data is limited [1.4.5, 1.4.7]. The drug passes into breast milk in small amounts, and its safety while breastfeeding should be discussed with a doctor [1.4.5].
- Loa loa Co-infection: Patients co-infected with the parasite Loa loa (African eye worm) may have severe reactions, including encephalopathy (a brain disease), especially with high microfilariae counts [1.4.4].
Conclusion: Prioritizing Safety with Ivermectin
To ensure your safety and the medication's effectiveness, always use ivermectin under the guidance of a healthcare professional. It is essential to provide your doctor with a complete medical history, including all pre-existing conditions and a full list of all medications, supplements, and herbal products you use. Take the medication exactly as prescribed, typically on an empty stomach with water [1.3.3]. Avoid consuming alcohol, which can exacerbate side effects [1.7.1].
Never self-medicate or use ivermectin formulations intended for animals, as these are highly concentrated and can be toxic to humans [1.6.2]. By being aware of what to avoid when taking ivermectin and maintaining open communication with your healthcare provider, you can minimize risks and achieve the intended therapeutic benefits.
For more authoritative information, you can visit the FDA's page on Ivermectin [1.6.1].
