I frequently see overdoses: why can large packs of medicines be bought over the counter?

I am an advanced clinical practitioner pharmacist working in acute medicine and, sadly, I often deal with drug overdoses.

I wondered if anyone has thoughts on why it is possible to buy 50 x 25mg promethazine tablets or 100 x 50 mg cyclizine tablets over the counter (OTC)? I appreciate that these items are not easily bought, owing to the careful questioning the pharmacist must undertake, but it seems strange that the pack sizes are so large.

Surely, people legitimately needing these quantities would be under a GP for their condition and would be able to produce an FP10? I’ve seen too many people with all sorts of problems from these overdoses: electrocardiogram changes or acute psychosis, for example. My medical colleagues are always absolutely horrified that these quantities can be bought OTC, and I cannot come up with any rationale for it.

Jessica di Gesso, advanced clinical practitioner in acute medicine, Cambridge University Hospitals NHS Foundation Trust