drug reactions

Prompt recognition of these reactions, drug withdrawl, and appropriate therapeutic interventions can minimize toxicity. Sulfonamide antibiotics, allupurinol, amine antiepileptic drugs (phenytoin and carbamazepine), lamotrigine, and the oxicam are associated with the highest risk of these reactions.
Pathogenesis of drug reactions
Cutaneus responses to drugs can arise as a result of immunologic or nonimmunologic mechanisms.
Immunologic :
Drug frequently elicit an immune response , but small number of individuals experience clinical hypersensitivity reactions . IgE dependent drug reactions are usually manifest in the skin and gastrointestinal, respiratory and cardiovascular systems. Primary symptoms and signs include pruritus, urticaria, nausea, vomiting, cramps, bronchospasm and laryngeal edema and occasion anaphylatic shock with hypotension and death.
Immune complex dependent reactions is characterized by fever, arthritis, arthritis, neuritis, edema, and an urticaria, popular, or purpuric rash. In classic serum sickness , symptoms develop 6 days or more after exposure to a drug, the latent period representing the time needed to synthesize antibody. The antibodies responsible are largely of the igG or igM class.
Cytotoxicity and delayed hypersensitivity may be important in the etiology of morbilliform exanthema, hypersensitivity syndrome , SJS , or TEN, but this is not proven.
Nonimmunologic drug reactions :
The mechanisms may be due to activation of effect pathways, overdosage , cumulative toxicity , side effects, ecologic disturbance , interactions between drugs, metabolic alterations , exaggeration of preexisting dermatologic conditions , or inherited protein or enzyme deficiencies.