Urticaria sulfonamides causing

Blood dyscrasias are quite uncommon, but if they occur may be serious enough to cause discontinuance of the therapy. Both topical and systemic adrninistration of sulfas can cause hypersensitivity reactions, such as urticaria, exfoHative dermatitis, photosensiti2ation, erythema nodosum, and in its most severe form, erythema multiformexudativum. (Stevens-Johnson syndrome). In general, however, use of sulfonamide therapy is considered relatively safe. 

Numerous systemic drugs have been implicated, including the penicillins and sulfonamides, which can cause swelling of the lids and conjunctiva as part of a generalized urticaria or localized angioneurotic edema. Other drugs implicated in ocular allergic reactions are antidepressants, antipsychotics, antihypertensives, antirheumatics, sedatives, and hypnotics. 

The following are the most common causes of drug-induced urticaria antibiotics, notably penicillin (more following parenteral administration than by ingestion), barbiturates, captopril, levamisole, NSAIDs, quinine, rifampin, sulfonamides, thiopental, and vancomycin. 

Sulfonamides or sulfones usually account for most toxicity associated with coadministration of these antifolate drugs (see Chapter 43). The combination of pyrimethamine (25 mg) and sulfa-doxine (500 mg) (fansidar) causes severe and even fatal cutaneous reactions in up to 1 in 5000 people. This combination also has been associated with serum sickness-type reactions, urticaria, exfoliative dermatitis, and hepatitis. Pyrimethamine-sulfadoxine is contraindicated in individuals with previous reactions to sulfonamides, lactating mothers, and infants <2 months of age. Administration of pyrimethamine with dapsone (MALOPRIM, unavailable in the U.S.), occasionally has been associated with agranulocytosis. Higher doses pyrimethamine (75 mg daily) used along... 

---