The British National Formulary (BNF) provides key information on the selection, prescribing, dispensing and administration of medicines.
Access the BNF here: https://bnf.nice.org.uk/
What you'll find:
Drug information- uses, doses, safety issues, and medicinal forms
Drug interactions checker
Treatment summaries by condition and body system
General prescribing guidance including renal impairment, palliative care, and prescription writing
Note: Also available as the BNFC (British National Formulary for Children) via the same site.