UK law caps how many painkiller tablets can be sold in a single pack. Under Schedule 15 of the Human Medicines Regulations 2012, ibuprofen, paracetamol and aspirin sold on general sale, such as in supermarkets, petrol stations and convenience shops, must come in packs of no more than 16 tablets or capsules. Pharmacies may sell larger packs, generally up to 32 tablets or capsules, under a pharmacist’s supervision, and it is illegal to sell more than 100 paracetamol or aspirin tablets in one transaction without a prescription; MHRA guidance also asks retailers to limit sales to two packs per transaction. The aim is to reduce accidental and impulsive overdoses: paracetamol overdose can cause fatal liver failure, and ibuprofen or aspirin overdose can cause gut bleeding and kidney failure. That is why the bottles of several hundred tablets common in U.S. stores are not sold over the counter in the UK.
Source: The Human Medicines Regulations 2012, Schedule 15 (legislation.gov.uk); MHRA — Best practice guidance on the sale of medicines for pain relief
Image: Ibuprofen packs on a pharmacy shelf. Maksym Kozlenko via Wikimedia Commons, public domain.