Side Effects of Stromectol (ivermectin)

Stromectol (ivermectin) is an anti-parasitic medication. Stromectol works by binding to invertebrate muscle and nerve cells of parasites, causing paralysis and death of parasites. 

Stromectol is active against the non-adult form of Onchocerca volvulus. Stromectol is also active against intestinal activity of Strongyloides stercoralis. Off-label use includes treatments for head lice, blepharitis, and filariasis.

Common side effects of Stromectol include

• itching,
• rash,
• dizziness,
• insomnia,
• abdominal pain,
• constipation,
• nausea, and
• vomiting.

Serious side effects of Stromectol include

• low blood pressure,
• facial swelling, and
• increased heart rate.

Drug interactions of Stromectol include warfarin because Stromectol can increase risks of bleeding and bruising when co-administered with warfarin. 

There are no adequate studies done on Stromectol to determine safe and effective use in pregnant women Stromectol should be avoided in pregnant mothers to avoid any risk to a fetus. 

Stromectol enters breast milk in trace amounts. It should be avoided in breastfeeding mothers to prevent any adverse effects to the newborn.

Common side effects of ivermectin are:

• itching,
• rash,
• dizziness,
• insomnia,
• abdominal pain,
• constipation,
• nausea, and
• vomiting.

Other side effects include:

• Low blood pressure,
• facial swelling, and
• increased heart.

Strongyloidiasis

In four clinical studies involving a total of 109 patients given either one or two doses of 170 to 200 mcg/kg of Stromectol (ivermectin) , the following adverse reactions were reported as possibly, probably, or definitely related to Stromectol (ivermectin):

Body as a Whole: asthenia/fatigue (0.9%), abdominal pain (0.9%)

Gastrointestinal: anorexia (0.9%), constipation (0.9%), diarrhea (1.8%), nausea (1.8%), vomiting (0.9%)

Nervous System/Psychiatric: dizziness (2.8%), somnolence (0.9%), vertigo (0.9%), tremor (0.9%)

Skin: pruritus (2.8%), rash (0.9%), and urticaria (0.9%).

In comparative trials, patients treated with Stromectol (ivermectin) experienced more abdominal distention and chest discomfort than patients treated with albendazole. However, Stromectol (ivermectin) was better tolerated than thiabendazole in comparative studies involving 37 patients treated with thiabendazole.

The Mazzotti-type and ophthalmologic reactions associated with the treatment of onchocerciasis or the disease itself would not be expected to occur in strongyloidiasis patients treated with Stromectol (ivermectin) .

Laboratory Test Findings

In clinical trials involving 109 patients given either one or two doses of 170 to 200 mcg/kg Stromectol (ivermectin) , the following laboratory abnormalities were seen regardless of drug relationship: elevation in ALT and/or AST (2%), decrease in leukocyte count (3%). Leukopenia and anemia were seen in one patient.

Onchocerciasis

In clinical trials involving 963 adult patients treated with 100 to 200 mcg/kg Stromectol (ivermectin) , worsening of the following Mazzotti reactions during the first 4 days post-treatment were reported:

• arthralgia/synovitis (9.3%),
• axillary lymph node enlargement and tenderness (11.0% and 4.4%, respectively),
• cervical lymph node enlargement and tenderness (5.3% and 1.2%, respectively),
• inguinal lymph node enlargement and tenderness (12.6% and 13.9%, respectively),
• other lymph node enlargement and tenderness (3.0% and 1.9%, respectively),
• pruritus (27.5%),
• skin involvement including edema, papular and pustular or frank urticarial rash (22.7%), and
• fever (22.6%).

In clinical trials, ophthalmological conditions were examined in 963 adult patients before treatment, at day 3, and months 3 and 6 after treatment with 100 to 200 mcg/kg Stromectol (ivermectin).

Changes observed were primarily deterioration from baseline 3 days post-treatment. Most changes either returned to baseline condition or improved over baseline severity at the month 3 and 6 visits. The percentages of patients with worsening of the following conditions at day 3, month 3 and 6, respectively, were:

• limbitis: 5.5%, 4.8%, and 3.5% and
• punctate opacity: 1.8%, 1.8%, and 1.4%.

The corresponding percentages for patients treated with placebo were:

• limbitis: 6.2%, 9.9%, and 9.4% and
• punctate opacity: 2.0%, 6.4%, and 7.2%.

In clinical trials involving 963 adult patients who received 100 to 200 mcg/kg Stromectol (ivermectin), the following clinical adverse reactions were reported as possibly, probably, or definitely related to the drug in ≥ 1% of the patients:

• facial edema (1.2%),
• peripheral edema (3.2%),
• orthostatic hypotension (1.1%), and
• tachycardia (3.5%).

Drug-related headache and myalgia occurred in < 1% of patients (0.2% and 0.4%, respectively). However, these were the most common adverse experiences reported overall during these trials regardless of causality (22.3% and 19.7%, respectively).

A similar safety profile was observed in an open study in pediatric patients ages 6 to 13.

The following ophthalmological side effects do occur due to the disease itself but have also been reported after treatment with Stromectol (ivermectin):

• abnormal sensation in the eyes,
• eyelid edema,
• anterior uveitis,
• conjunctivitis,
• limbitis,
• keratitis, and
• chorioretinitis or choroiditis.

These have rarely been severe or associated with loss of vision and have generally resolved without corticosteroid treatment.

Laboratory Test Findings

In controlled clinical trials, the following laboratory adverse experiences were reported as possibly, probably, or definitely related to the drug in ≥ 1% of the patients: eosinophilia (3%) and hemoglobin increase (1%).

Post-Marketing Experience

The following adverse reactions have been reported since the drug was registered overseas:

Onchocerciasis

Conjunctival hemorrhage

All Indications

Hypotension (mainly orthostatic hypotension), worsening of bronchial asthma, toxic epidermal necrolysis, Stevens-Johnson syndrome, seizures, hepatitis, elevation of liver enzymes, and elevation of bilirubin.

Post-marketing reports of increased INR (International Normalized Ratio) have been rarely reported when ivermectin was co-administered with warfarin.