Harrison's Internal Medicine Chapter 56. Cutaneous Drug Reactions CUTANEOUS DRUG REACTIONS: INTRODUCTION Cutaneous 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. . | Chapter 056. Cutaneous Drug Reactions Part 1 Harrison s Internal Medicine Chapter 56. Cutaneous Drug Reactions CUTANEOUS DRUG REACTIONS INTRODUCTION Cutaneous 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. USE OF PRESCRIPTION DRUGS IN THE UNITED STATES In the United States more than 3 billion prescriptions for over 60 000 drug products which include more than 2000 different active agents are dispensed annually. Hospital inpatients alone annually receive about 120 million courses of drug therapy and half of adult Americans receive prescription drugs on a regular outpatient basis. Many additional patients use over-the-counter medicines that may cause adverse cutaneous reactions. INCIDENCE OF CUTANEOUS REACTIONS Several large cohort studies established that acute cutaneous reaction to drugs affected about 3 of hospital inpatients. Reactions usually occur a few days to 4 weeks after initiation of therapy. Many drugs of common use are associated with a 1-2 rate of rashes during premarketing clinical trials. The risk is often higher when medications are used in general unselected populations. The rate may reach 3-7 for amoxicillin sulfamethoxazole and many anticonvulsants Table 56-1 . It may be even higher with anti-HIV agents. Table 56-1 Cutaneous Reactions to Drugs Received by at Least 1000 Patients BCDSP fl Drug Reactio ns No. Recipien ts No. Rat e 95 Confiden ce Interval Amoxicillin 63 1225 Ampicillin 215 4763 Co-trimoxazole 46 1235 Semisyntheti
