Diazepam is a benzodiazepine with several clinical uses, including managing anxiety, insomnia, muscle spasms, seizures, and alcohol withdrawal (1). Brand names include Valium, Diastat Acudial, Diastat, and Diazepam Intensol.
Diazepam is primarily metabolized by CYP3A4 and CYP2C19 to the major active metabolite, desmethyldiazepam. Approximately 2% of Europeans, 13% of East Asians, and as much as 57% of Oceanians have reduced or absent CYP2C19 enzyme activity (“poor metabolizers”) (2).
The FDA-approved drug label for diazepam gel states that “the marked inter-individual variability in the clearance of diazepam reported in the literature is probably attributable to variability of CYP2C19”(3). However, the most recent drug label for oral formulations (tablet and liquid) only briefly discusses CYP2C19 in the context of potential drug interactions (Table 1)(1). Diazepam is available in multiple formulations including tablets (1), rectal gel (3), injectable solution (4), and oral solutions (5). The injectable solution does not discuss potential pharmacogenetic interactions with CYP2C19.