If you have an itchy, ring-shaped rash on your skin, you may have ringworm of the body, also known as tinea corporis. Ringworm is not an actual worm but a simple fungal infection that is easily treatable with prescription medication. One medication used in ringworm treatment is ketoconazole, which you can take topically or orally.
If you have a ringworm infection of your skin that does not clear up on its own or respond to over-the-counter treatments, your doctor may prescribe a strong topical medication called ketoconazole. According to the Mayo Clinic, this anti-fungal drug is used for all forms of ringworm, as well as yeast infections and seborrheic dermatitis, and is one of many topical ringworm medications that your doctor may prescribe to help treat an infection. It is available in a variety of forms, such as gel, shampoo or cream. Your doctor will help you choose which type to use depending on the infection's location on your body.
Like most medications, you should use all of the prescribed ketoconazole according to your doctor's instructions, even if your skin begins to feel better. The medication is typically applied daily to the affected skin and surrounding areas, though the proper dosage may vary depending on the severity of your condition. Possible side effects include skin irritation and itching, dizziness and dry eyes.
If the topical form of the medication fails to adequately treat your ringworm infection, your doctor may prescribe oral ketoconazole. This treatment is also used by those who are unable to take griseofulvin, a commonly used type of oral anti-fungal medication. Unlike topical ketoconazole, the oral route is usually prescribed for more serious fungal infections of the skin, including blastomycosis and paracoccidioidomycosis. According to the Mayo Clinic, oral ketoconazole is available only in tablet form via a doctor's prescription.
The most commonly used dose of the drug is approximately 200 mg once a day, though this will of course vary depending on your overall health and the severity of your condition. Like the topical treatment, use your entire prescription of oral ketoconazole, even if your ringworm infection resolves within a few days. The side effects of the drug are myriad but rarely serious, and can include headache, dizziness and chest pains.