What Is a Fixed Drug Reaction?

A fixed drug reaction, often referred to as a fixed drug eruption, is a skin rash which may develop in susceptible people to a medication that they have taken. A person who develops this reaction to a drug is likely to have it again if the drug is re-administered. The rash usually resolves on withdrawal of the medication but may leave hyperpigmentation, which is a patchy, darkening of the skin. Generally, it is just a skin manifestation and is not accompanied by systemic effects.

Drugs may cause adverse side effects in some people. These may be dermatological and can range from mild rash or itching to more serious, potentially fatal skin reactions such as Stevens-Johnson Syndrome. A fixed drug reaction is generally not dangerous, but can be uncomfortable and physically disfiguring. Any skin reaction to a drug should be seen urgently by a medical professional for diagnosis and possible withdrawal of treatment.

The development of a fixed drug reaction may occur half an hour to eight hours after administration of the causative drug. Rarely the first reaction may only develop within two weeks of initiation of the drug. It may occur anywhere on the body but the most common places are the hands and feet and genitals. The eyes and mouth may also be affected. The skin lesions are usually round, red, and may be slightly swollen and are occasionally accompanied by blistering.

The hyperpigmentation that may persist after the reaction has been resolved may appear darker on those with dark skin. If the drug is administered again, lesions usually appear in the same place and may spread. More serious skin reactions can be associated with systemic effects such as fever or liver dysfunction.

The main action in the treatment of a fixed drug reaction is to establish the cause and remove the causative agent. It may be caused by a number of drugs, including prescription, over-the-counter and complementary medicines. Any medication, including homeopathic therapies, should be discussed with the doctor. Occasionally antihistamines or topical corticosteroids may be given to treat symptoms of itching and swelling.

If a fixed drug reaction has been experienced, the causative drug should be avoided. Some cases of desensitization have been reported but this should only be attempted if no alternative drug is available, and should be done under a specialist's supervision. Should any adverse reaction occur while taking medication, medical attention should be sought urgently.