This Handbook from the UK Clinical Pharmacy Association is a useful reference on general perioperative drug management. This handbook is supported by The Centre for Perioperative Care (Royal College of Anaesthetists).
For medication management guidelines, see: https://perioptalk.org/medication/
Management of immunomodulators is not included, see: https://perioptalk.org/immunomodulators-perioperative-management/
For drug interactions consider using Lexicomp Drug Interactions via UpToDate (via CIAP)