DefinePK

Abstract

Introduction


Drug eruptions are common cutaneous disorders encountered by dermatologists. Some drug eruptions. although trivial, may cause cosmetic embarrassment and fixed drug eruption (FDE) is one of them1,2. FDE is characterized by an appearance of round or oval apparently oedematous plaques, which vary in size from few millimeters to more than ten centimeters. It may affect any part of the skin and/or mucous membrane. A patient may have multiple lesions or rarely generalized form of bullous FDE2 with or without mucous membrane involvement and constitutional symptoms. The diagnostic hallmark is its recurrence at previously affected sites.
Most workers believe that FDE is caused solely by drugs3. Rarely, non-drug factors such as cold, dyes in food stuffs or pills,dysmenorrhea, fatigue, heat, ingestion of peas, beans or lentils, ipecac, karaya gum, legumes, menstruation, pregnancy, psychic factors, saccharin, ultraviolet rays and undue effort may result in fixed eruption. The FDE may be caused by a singleormultiple drugs4. It is commonly seen with various antimicrobials, analgesics, neurologic and psychiatric drugs. When eruptionoccurs with drugs closely related in their chemical structure, the phenomenon is tenned as “Cross-sensitivity”. When drugs of totally different chemical structures precipitate exacerbation, this reaction is called ‘Polyallergic sensitization, or Polysensitivity4”.
The exact pathogenic mechanism of FDE remains unknown. Both the immunological and toxic mechanisms have been implicated but conclusive evidence is lacking.
To ascertain the specific drug causing eruption, history remains the most important tool. The diagnosis can be made on the basis of clinical appearance and course. There is consensus that only a provocation test with the suspected drug will provide certainly about its role in an eruption.
In general, fixed eruption due to the drug is considered if tile skin lesion flares up with appearance of burning and/or pruritus, erythema and oederna6. If the result is negative till 24 hours or 24-48 hours, a larger dose of the same drug or an initial dose of another suspected drug is given.
Sometimes general symptoms in the form of malaise, prostration, fever, nausea, vomiting, diarrhoea, abdominal cramps are seen4.