The Full Story
Scabies occurs when one is infested with the parasitic mite Sarcoptes scabiei. Scabies might be the oldest documented human skin disease and is spread through skin-to-skin contact. While scabies mites are very small, they are visible to the human eye. Scabies mites have 8 legs, sharing a part of their genetic tree with spiders and ticks.
Crotamiton was developed in the 1940s as a treatment for scabies. It kills scabies mites by an unknown mechanism and has antihistamine activity (think Benadryl) that helps with the itching associated with scabies. Standards for drug development were not as stringent in the 40s, but crotamiton was used in adults and children with few reported adverse effects. When tougher standards were enacted, use of crotamiton was "grandfathered" in, because it worked well and seemed safe. Users have reported warm feelings in the areas where crotamiton is applied, localized skin irritation, itching, and rash. Hypersensitivity reactions have also been reported.
In the US, crotamiton comes as a 10% lotion (Crotan). This formulation contains benzyl alcohol, cetyl alcohol, and propylene glycol. These ingredients have their own toxicities and could potentially cause problems if applied in excess on the skin of children. Benzyl alcohol can cause methemoglobinemia if too much is applied or if it is applied too frequently. Methemoglobinemia impairs the red blood cells from carrying oxygen to the body.
It is important to use crotamiton as prescribed. One criticism of crotamiton is that there is not a standardized way to use it. Crotamiton lotion is usually applied from the chin down to the soles of the feet after taking a bath or shower. After the first application, a second application might be recommended 24 hours later. Some regimens require a 5-day course.
Permethrin is now the most commonly used first-line treatment for scabies in the US. It is more effective than crotamiton in stopping a scabies infestation and has a similar side effect profile.
If you are worried about a crotamiton exposure, check the webPOISONCONTROL® online tool for guidance or call Poison Control at 1-800-222-1222. Whether you log on or call, expert assistance is available 24 hours a day.
Pela Soto, PharmD, BSHS Pharmacogenomics, BS Microbiology
Certified Specialist in Poison Information
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- When crotamiton is prescribed for a child, an adult must manage its application.
- Keep crotamiton lotion up and out of reach of children.
This Really Happened
A 23-year-old woman drank an unknown amount of crotamiton 10% to harm herself after an argument. Her family attempted to induce vomiting with salt water (which is never recommended, and can actually cause more toxicity) and took her to the hospital. The medical team performed decontamination of her stomach, including gastric lavage (washing out the stomach, also called "stomach pumping") and they gave her activated charcoal. Shortly thereafter, she had three tonic-clonic seizures. She was treated for the seizures and was sedated. She developed low blood pressure and abnormal muscle movements that were concerning for neurological damage.
The results of her blood lab work were normal, and crotamiton was confirmed to be present in her blood. She made a full recovery and was discharged from the hospital 6 days later without any remaining issues (from Meredith et al., 1990).