Common Side Effects of Oral Ivermectin
When taken orally as prescribed by a healthcare provider for approved conditions, ivermectin can cause several mild, and generally temporary, side effects. These reactions are often less severe during retreatment.
- Gastrointestinal Issues: Mild side effects commonly include nausea, vomiting, diarrhea, abdominal pain, and loss of appetite.
- Neurological Symptoms: Some individuals may experience dizziness, sleepiness, or uncontrollable shaking (tremors).
- Systemic Discomfort: Other reported common effects include fatigue, muscle pain, joint pain, and constipation.
- Skin Reactions: Itching (pruritus) is a particularly common side effect, especially in people being treated for onchocerciasis, and can be related to the parasites dying in the skin. A mild rash may also occur.
Serious and Less Common Side Effects
Though less frequent, more serious adverse reactions can occur with ivermectin. It is crucial for patients to seek immediate medical attention if they experience any of these symptoms.
- Neurological Problems: Severe neurological effects are a major concern, particularly with higher-than-prescribed doses or in sensitive individuals. These can include confusion, disorientation, severe sleepiness, seizures, and in the most severe cases, coma or death. Studies have documented cases of encephalopathy and other neurotoxic effects, especially in individuals with compromised blood-brain barriers or pre-existing conditions.
- Serious Skin Reactions: In rare instances, ivermectin can trigger severe skin conditions like Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Early symptoms often resemble the flu and progress to widespread blistering and peeling of the skin.
- Liver Damage: Ivermectin can cause elevated liver enzymes and, rarely, more serious liver injury or hepatitis. Symptoms may include jaundice (yellowing of the skin and eyes), abdominal pain, and dark urine.
- Mazzotti Reaction: In patients being treated for onchocerciasis (river blindness), the killing of microfilariae by ivermectin can cause a significant inflammatory response known as the Mazzotti reaction. Symptoms include fever, rash, joint pain, swollen lymph nodes, rapid heartbeat, and swelling of the face and limbs.
- Cardiac Effects: Orthostatic hypotension (a drop in blood pressure when standing) and an increased heart rate (tachycardia) have been reported.
- Serious Eye Problems: In patients with onchocerciasis, severe eye inflammation and even vision loss can occur, though these effects are also part of the disease itself.
Topical Ivermectin Side Effects
Ivermectin is also available in topical formulations for treating conditions like head lice and rosacea. The side effects for these formulations are generally localized and milder than the systemic effects of the oral tablet.
- Local Skin Irritation: Side effects include burning, itching, redness, dryness, and irritation of the skin or scalp.
- Dandruff: Patients using ivermectin lotion for head lice may experience dandruff.
- Eye Irritation: Irritation or excessive tearing in the eyes can occur.
- Systemic Risks: Though rare with proper use, overdose of topical formulations can lead to systemic side effects similar to those seen with oral overdose, such as neurological issues.
Ivermectin Overdose and Misuse
Misuse of ivermectin, particularly taking large doses or using animal formulations, is extremely dangerous and can lead to severe toxicity. Animal products contain significantly higher concentrations of the drug and are not formulated for human consumption.
Overdose symptoms can include:
- Gastrointestinal distress (severe nausea, vomiting, diarrhea)
- Neurological effects (confusion, seizures, lack of coordination, severe sleepiness, coma)
- Low blood pressure (hypotension)
- Shortness of breath
- Swelling of the face, limbs, or entire body
- Death
Comparison Table: Common vs. Serious Ivermectin Side Effects
| Aspect | Common Side Effects | Serious Side Effects |
|---|---|---|
| Symptom Type | Generally mild and temporary | Potentially life-threatening, requiring medical intervention |
| Gastrointestinal | Nausea, vomiting, diarrhea, stomach pain, loss of appetite | Severe gastrointestinal distress and abdominal pain in overdose |
| Neurological | Dizziness, sleepiness, tremors | Confusion, seizures, coma, encephalopathy, severe unresponsiveness |
| Dermatological | Itching, mild rash, hives | Severe, widespread blistering and peeling skin (SJS/TEN) |
| Systemic/Allergic | Fatigue, muscle/joint pain, swollen lymph nodes (with onchocerciasis) | Mazzotti reaction, severe allergic reactions, swelling of face/limbs |
| Cardiovascular | N/A | Low blood pressure (hypotension), increased heart rate (tachycardia) |
| Likelihood | Occur in some patients at therapeutic doses | Rare with therapeutic doses; significantly higher with overdose |
Conclusion
While ivermectin is an effective treatment for certain parasitic infections, patients and healthcare providers must be aware of the potential side effects, both common and serious. Mild gastrointestinal and neurological symptoms are most frequent, but severe neurological events, liver damage, and severe skin reactions are rare but possible, especially with overdose. It is critical to use only FDA-approved human-grade formulations under a doctor's supervision and at the correct dosage. The risks associated with misuse, particularly the use of animal formulations, are significant and can lead to severe toxicity or death. The Mazzotti reaction is a specific inflammatory response to treatment for onchocerciasis that also requires careful management. For comprehensive information on proper dosing, potential drug interactions, and safety precautions, patients should always consult their physician based on information from the Mayo Clinic.
Who Is at Higher Risk for Side Effects?
Certain individuals are at higher risk for experiencing serious side effects from ivermectin. This includes people with pre-existing liver problems, as the drug can cause elevated liver enzymes. Individuals with conditions affecting the immune system, such as HIV, may also require closer monitoring. A specific risk involves co-infection with the parasite Loa loa, which can lead to life-threatening brain inflammation (encephalopathy) after ivermectin treatment.
What to Do If You Experience Side Effects
Patients should report any side effects to their doctor. For mild symptoms like nausea or fatigue, your doctor may offer guidance on managing them. However, if you experience any serious symptoms like severe dizziness, seizures, vision changes, or signs of a serious skin or allergic reaction, you should seek emergency medical care immediately. If an overdose is suspected, contact a poison control center immediately.
The Role of Ivermectin in Public Health
Ivermectin has been a crucial tool in public health campaigns to eradicate parasitic diseases like onchocerciasis in certain regions. The adverse effects are generally well-managed in these controlled, supervised programs. The drug's safety profile is well-established when used appropriately for its approved indications. However, the misuse of ivermectin, especially concerning unapproved uses like COVID-19, has led to a rise in reported toxic exposures and severe adverse events.
This article aims to inform and educate about the potential risks associated with ivermectin, highlighting the importance of adhering to medical advice and understanding the proper indications for its use.
