From the FDA Drug Label
This drug is known to be substantially excreted by the kidney However, since topical permethrin is metabolized in the liver and excreted in the urine as inactive metabolites, there does not appear to be an increased risk of toxic reactions in patients with impaired renal function when used as labeled.
The use of permethrin in patients with abnormal liver function tests is not directly addressed in the provided drug label. However, it is mentioned that permethrin is metabolized in the liver.
- There is no explicit warning regarding the use of permethrin in patients with abnormal liver function tests.
- The label does mention that permethrin is excreted in the urine as inactive metabolites. Given the lack of direct information, a conservative clinical decision would be to exercise caution when using permethrin in patients with abnormal liver function tests, as the potential effects on liver function are not clearly stated 1.
From the Research
Permethrin is generally considered safe for patients with abnormal liver function tests (LFTs) as it has minimal systemic absorption when applied topically. The standard treatment for scabies and lice involves applying 5% permethrin cream from neck to toes, leaving it on for 8-14 hours, then washing it off. Unlike oral medications that require hepatic metabolism, permethrin works locally on the skin with less than 2% being absorbed into the bloodstream. This limited systemic exposure means that liver impairment typically doesn't significantly affect permethrin's safety profile or require dose adjustments.
However, patients with severe liver disease or those with extensive skin breakdown (which could increase absorption) should be monitored more closely for potential adverse effects. If treating a patient with significantly compromised liver function, consider consulting with a specialist before treatment, though alternatives like benzyl benzoate may have more hepatic concerns 2, 3, 4. The most common side effects of permethrin are mild skin irritation, burning, or stinging at the application site rather than systemic effects. It's worth noting that while ivermectin has been associated with liver injury in some cases 5, 6, permethrin has a different mechanism of action and is not typically associated with significant liver toxicity.
Some key points to consider when evaluating patients with abnormal LFTs include:
- The pattern and severity of liver injury can provide clues about the cause of disease and should guide diagnostic evaluation 3, 4
- A systematic, stepwise approach to the evaluation and management of abnormal liver test results is recommended to optimize high-value care 3
- Patient with signs or symptoms of liver disease or abnormal liver test results should be evaluated to determine the etiology 4
- Tests should include a complete blood cell count; alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, and albumin levels; prothrombin time; hepatitis B surface antigen; hepatitis B core antibody; hepatitis C antibody; ferritin and iron levels and transferrin saturation; and right upper quadrant abdominal ultrasonography 4.