Chapter 056. Cutaneous Drug Reactions (Part 1)

Harrisons Internal Medicine Chapter 56. Cutaneous Drug ReactionsCUTANEOUS DRUG REACTIONS: INTRODUCTIONCutaneous reactions are among the most frequent adverse reactions to drugs. Every physician will see patients suffering from them. Most are benign, but a few can be life-threatening. Prompt recognition of severe reactions, drug withdrawal, and appropriate therapeutic interventions can minimize toxicity. This chapter focuses on adverse cutaneous reactions to drugs other than topical agents; it covers their incidence, patterns, and pathogenesis and provides some practical guidelines on treatment, assessment of causality, and future utilization of drugs. ...
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Chapter 056. Cutaneous Drug Reactions (Part 1) Chapter 056. Cutaneous Drug Reactions (Part 1) Harrisons Internal Medicine > Chapter 56. Cutaneous Drug Reactions CUTANEOUS DRUG REACTIONS: INTRODUCTION Cutaneous reactions are among the most frequent adverse reactions todrugs. Every physician will see patients suffering from them. Most are benign, buta few can be life-threatening. Prompt recognition of severe reactions, drugwithdrawal, and appropriate therapeutic interventions can minimize toxicity. Thischapter focuses on adverse cutaneous reactions to drugs other than topical agents;it covers their incidence, patterns, and pathogenesis and provides some practicalguidelines on treatment, assessment of causality, and future utilization of drugs. USE OF PRESCRIPTION DRUGS IN THE UNITED STATES In the United States more than 3 billion prescriptions for over 60,000 drugproducts, which include more than 2000 different active agents, are dispensedannually. Hospital inpatients alone annually receive about 120 million courses ofdrug therapy, and half of adult Americans receive prescription drugs on a regularoutpatient basis. Many additional patients use over-the-counter medicines thatmay cause adverse cutaneous reactions. INCIDENCE OF CUTANEOUS REACTIONS Several large cohort studies established that acute cutaneous reaction todrugs affected about 3% of hospital inpatients. Reactions usually occur a few daysto 4 weeks after initiation of therapy. Many drugs of common use are associated with a 1–2% rate of rashesduring premarketing clinical trials. The risk is often higher when medications areused in general unselected populations. The rate may reach 3–7% for amoxicillin,sulfamethoxazole, and many anticonvulsants (Table 56-1). It may be even higherwith anti-HIV agents. Table 56-1 Cutaneous Reactions to Drugs Received by at Least 1000Patients (BCDSP)a Drug Reactio Recipien Rat 95 ns, No. ts, No. e, % % Confiden ce Interval Amoxicillin 63 1225 5.1 3.9 –6.4 Ampicillin 215 4763 4.5 3.9 –5.1 Co- 46 1235 3.7 2.7trimoxazole –4.8 Semisyntheti 41 1436 2.9 2.0c penicillins –3.7 Red blood 67 3386 2.0 1.5cells –2.4 Penicillin G 68 4204 1.6 1.2 –2.0 Cephalospor 27 1781 1.5 0.9ins –2.1 Gentamicin 13 1277 1.0 0.5 –1.6 a BCDSP, Boston Collaborative Drug Surveillance Program. Source: Adapted from Bigby. In addition to acute eruptions, a variety of skin diseases can be induced orexacerbated by prolonged utilization of drugs, e.g., pruritus, pigmentation, nail orhair disorders, psoriasis, and pemphigus. These chronic drug reactions are notfrequent, but neither their incidence nor their impact on public health has beenevaluated. In a series of 48,005 inpatients over a 20-year period, morbilliform rash(91%) and urticaria (6%) were the most frequent skin reactions. Severe reactionsare actually too rare to be detected in such cohorts. Their incidence has beenestimated to be in the range of 1 in 10,000 to 1 in 1 million users. Even thoughthey are rare, severe cutaneous reactions to drugs have an important impact onhealth and on the risk-versus-benefit evaluation of medicines because ofsignificant mortality and sequelae. Some populations are at increased risks of drug reactions: patients withcollagen vascular diseases, bone marrow graft recipients, and those with acuteEpstein-Barr virus in ...