Ivermectin tablets are usually taken as a single dose and most people tolerate them well. This guide covers the side effects to expect, the ones that need a doctor, and the warning signs of taking too much.
Common side effects of ivermectin tablets
- dizziness
- nausea, diarrhoea or stomach pain
- tiredness or lack of energy
- itching or a mild rash
These are usually mild and pass within a day or two.
Reactions to dying parasites
When ivermectin is used for river blindness (onchocerciasis), the body can react to the parasites as they die. This is called the Mazzotti reaction. It can cause itching, fever, swollen glands, joint pain and, less often, a drop in blood pressure that makes you dizzy when you stand up. Lie down if you feel faint and tell your doctor.
Serious side effects: get medical help
- a severe skin rash with blistering or peeling
- yellowing of the skin or eyes, or dark urine
- confusion, extreme sleepiness or difficulty walking
- seizures
- swelling of the face, lips or throat, or difficulty breathing
Overdose warning signs
Most ivermectin overdoses in the US have involved animal products or taking more than prescribed. Signs include:
- nausea, vomiting and diarrhoea
- confusion, drowsiness or hallucinations
- unsteady walking, tremor
- blurred vision
- low blood pressure, seizures or coma
If you think someone has taken too much, call Poison Control on 1-800-222-1222, or 911 if they are very drowsy, having a seizure or struggling to breathe.
Medicines that interact with ivermectin
- Warfarin: there are reports of a raised INR (increased bleeding risk), so your INR may need checking.
- Sedatives such as benzodiazepines or barbiturates: tell your doctor if you take these.
- Some medicines that change how the liver breaks down drugs, including certain HIV medicines, antifungals and ciclosporin. Your pharmacist can check your list.
Side effects of ivermectin lotion and cream
The lotion used for head lice and the cream used for rosacea are applied to the skin, so very little reaches the bloodstream. Possible effects include eye irritation, redness, burning, dry skin or dandruff. Keep them away from the eyes.
See also: what ivermectin is used for, and what it doesn’t treat.
More in our Lice and Parasites guide: all our articles on this topic in one place.
This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.
