Internal Medicine

P1: RLJ/OZN P2: KUF

0521779407-D-01 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 7:41

498 Drug Allergy

Risk Factors

■Concomitant medication (eg, allopurinol w/ aminopenicillins)

■Concomitant disease (e.g., AIDS & sulfonamides, EB virus &

aminopenicillins, renal disease & allopurinol)

■Requirement for repeated treatment (eg, chronic sinusitis, immun-

odeficiency disease, cystic fibrosis)

■Hospitalized pts receive an average of 10 different drugs, have∼10%

risk of drug reaction overall, increasing w/ the number of agents to

which they are exposed

Types of Reactions

■Systemic

➣Anaphylaxis (hypotension or, rarely, bronchospasm)

➣Serum sickness: arthritis, skin rash (including vasculitis), glo-

merulonephritis, cerebritis

■Cutaneous

➣Maculopapular, pruritic, resembling viral exanthem, onset∼^1

week after beginning treatment

➣Urticaria: intensely pruritic raised hives, coming in crops,±sub-

cutaneous swelling of hands, face, oropharynx

➣Eczematous dermatitis: chronic scaling on erythematous base

Photosensitive dermatitis: pruritic, erythematous, scaling in

sun-exposed areas

Erythema nodosum: indurated, tender nodular lesions on

extremities, heal w/ ecchymosis

Mucocutaneous eruptions (Stevens-Johnson syndrome): bul-

lae, target lesions, mucous membrane lesions

Toxic epidermal necrolysis: widespread skin exfoliation, po-

tentially fatal

Vasculitis: palpable purpuric lesions, lasting several days, often

ulcerating

■Lupus-like syndrome: rash, arthralgia, positive ANA (internal organ

involvement unusual)

➣Procainamide, hyralazine, phenytoin, thiouracil, quinidine

■Hematologic

➣Eosinophilia

➣Hemolytic anemia

➣Leukopenia

➣Thrombocytopenia

➣Pancytopenia (marrow aplasia)

■Renal

➣Interstitial nephritis