GENERIC SUBSTITUTION OF NTI DRUGS - ISSUES FOR FORMULARY COMMITTEE CONSIDERATION

Considerable controversy has developed during the last few years over generic substitution of drugs with a narrow therapeutic index (NTI). T he issue is complicated because there is no definitive list of which m edications should be classified as NTI drugs, most of the evidence of clinical problems related to generic substitution of these drugs comes from anecdotal case reports, and few practitioners are fully knowledg eable about exactly what constitutes generic substitution. The real qu estion is the ''switchability'' of generic equivalents for patients wh o are stabilized on NTI drugs, not the ''prescribability'' of generic equivalents at the initiation of therapy. If switchability is consider ed a potential clinical problem for a given drug, formulary policies a nd patient care plans should take into account the difficulties that d ispensing pharmacists face when trying to avoid switches among differe nt manufacturers' versions of that drug.