In 2017 the BNF interactions were rewritten to be more consistently structured, allowing users to find interactions more easily, and giving more information about the severity and evidence of an interaction. All interactions are listed under individual drugs. When checking interactions for combination drugs or co-drugs, it is essential to refer to each drug in the combination. The interactions section of the drug monograph clearly states the drugs (or drug classes) that need to be referred to in the interactions (Appendix 1 in print).
Please note that co-trimoxazole currently has its own entry in print that does not include the interactions for trimethoprim. As stated above, it is essential to refer to both drugs (trimethoprim and sulfamethoxazole, under sulfonamides) to find all relevant interactions for this drug. This inconsistency will be corrected in the upcoming September editions, BNF 78 and BNF for Children 2019-2020. Digital products including MedicinesComplete and the BNF app have been corrected for the June monthly update.