Supplements and benzodiazepines.
Benzodiazepines (diazepam, lorazepam, temazepam) potentiate GABA at the GABA-A receptor. Several supplements act on the same axis. Combining them adds sedation in a way that is sometimes useful and often overshoots.
Kava is the clearest exclusion: independent hepatotoxicity risk (the UK MHRA suspended kava-containing medicines for human consumption in 2003) plus additive GABAergic sedation. Valerian and passionflower add CNS depression in a softer, dose-dependent way; the Akhondzadeh 2001 RCT found passionflower clinically comparable to oxazepam for generalised anxiety, which gives you a sense of the additive potential. Ashwagandha is theoretical-only at this stage but worth flagging. Note that St John’s Wort reduces diazepam levels (CYP3A4) but does not affect lorazepam or temazepam, which are glucuronidated rather than CYP3A4-metabolised. The class page pre-selects all three benzodiazepines.
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If a supplement or medication you take isn't in our autocomplete, tell us and we'll add it in the next quarterly update.