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January 13, 1999

Nevirapine, Didanosine, and Zidovudine for Patients With HIV: The INCAS Trial

Author Affiliations

Margaret A.WinklerMDIndividualAuthorPhil B.FontanarosaMD, Senior EditorsIndividualAuthor

JAMA. 1999;281(2):130-131. doi:10-1001/pubs.JAMA-ISSN-0098-7484-281-2-jac80019

To the Editor: The Editorial regarding HIV treatment by Dr Gulick1 states that "the clinician has access to a total of 13 antiretroviral agents approved by the Food and Drug Administration, with a theoretical 1716 triple combinations from which to choose." The number 1716 represents the number of permutations of 3 of the 13 agents (13 × 12 × 11). There are 286 combinations of 3 of the 13 agents: (13 × 12 × 11)/(3 × 2 × 1). The number of permutations reflects the number of therapeutic options only if the order in which the drugs is given is of importance. Since all drugs are given simultaneously, the correct number of theoretical options is 286, which is still a formidable challenge for clinicians.