Side Effects of Ivermectin
Ivermectin can cause various side effects ranging from mild to severe, with the most common being dizziness, nausea, fever, headache, muscle/joint pain, and skin reactions, while serious adverse effects are rare when used at approved doses for parasitic infections. 1, 2
Common Side Effects
- Mild reactions: Dizziness, nausea, fever, headache, muscle or joint pain, and pruritus (itching) are the most frequently reported side effects 1, 2
- Skin reactions: Rash, urticaria (hives), and contact dermatitis may occur after treatment 2
- Gastrointestinal effects: Abdominal pain, nausea, vomiting, and diarrhea are commonly reported 2, 3
- Mazzotti reaction: When used for onchocerciasis, patients may experience tender lymphadenopathy, headache, bone/joint pain, fever, urticaria, and asthma due to microfilarial death 1
Severe Side Effects (Rare)
- Neurological effects: At high doses, ivermectin may cross the blood-brain barrier causing ataxia (loss of coordination), seizures, confusion, and coma 2, 4
- Encephalopathy: Patients with onchocerciasis who are also heavily infected with Loa loa may develop serious or even fatal encephalopathy following treatment 2
- Hepatic effects: Rare cases of elevated liver enzymes and hepatitis have been reported 5
- Cardiac effects: Rare cases of sinus tachycardia have been documented, particularly in elderly patients 5
Risk Factors for Adverse Effects
- Loa loa co-infection: Patients with concurrent Loa loa infection are at higher risk for serious neurological adverse effects 2
- Weight under 15 kg: Safety not established in children weighing less than 15 kg 2
- P-glycoprotein deficiency: Genetic polymorphisms in P-glycoprotein or co-administration of P-glycoprotein inhibitors may increase neurotoxicity 4
- Liver disease: Patients with severe liver disease may be at higher risk for toxicity 6
- Elderly patients: May be more susceptible to adverse effects due to decreased organ function 2, 5
Overdose Symptoms
- Neurological symptoms: Ataxia, seizures, decreased consciousness, and visual hallucinations 2, 7
- Systemic effects: Hypotension, respiratory depression, and edema may occur with significant overdose 2
- Other effects: Mydriasis (pupil dilation), paresthesia, and urticaria have been reported 2
Management of Adverse Effects
- Supportive care: Most mild reactions are self-limiting and require only symptomatic management 2
- For overdose: Treatment includes parenteral fluids, respiratory support, and pressor agents if significant hypotension occurs 2
- Decontamination: Induction of emesis, gastric lavage, and activated charcoal may be indicated to prevent absorption of ingested material 2, 7
- Topical reactions: Topical corticosteroids and oral antihistamines may help relieve skin inflammation 1
Special Considerations
- Pregnancy: Ivermectin should not be used during pregnancy as safety has not been established 2
- Breastfeeding: Ivermectin is excreted in human milk in low concentrations; treatment of mothers who intend to breastfeed should only be undertaken when benefits outweigh risks 2
- Drug interactions: Increased INR has been reported when co-administered with warfarin 2
- Food interactions: High-fat food increases bioavailability by 2.5 times; take on an empty stomach with water 1
Monitoring Recommendations
- Pretreatment assessment: For individuals with significant exposure to Loa loa-endemic areas, pretreatment assessment for loiasis should be implemented 2
- Post-treatment follow-up: Careful monitoring is recommended, especially in high-risk populations 2
- Laboratory monitoring: Consider monitoring liver function tests in patients with pre-existing liver conditions 5
Ivermectin is generally well-tolerated when used at appropriate doses for approved indications, with most adverse effects being mild and transient 4, 3. However, caution should be exercised in specific populations, and proper dosing is essential to minimize the risk of adverse effects 6, 2.