Which medicines to continue or stop before surgery

What it is

A full medication history, including over-the-counter and herbal products, is part of every pre-anaesthetic visit. The rule of thumb is to continue medicines whose withdrawal is dangerous or that protect the patient (beta-blockers, statins, inhalers, antiepileptics, thyroid replacement, antiparkinson drugs, most psychiatric drugs and long-term corticosteroids) and to pause those that add risk under anaesthesia or while fasting. ACE inhibitors and angiotensin receptor blockers are often held on the day of surgery because they can cause hypotension after induction that responds poorly to usual vasopressors; diuretics are commonly held that morning too. Diabetes drugs are adjusted for the fast: metformin and sulfonylureas are usually held on the day, SGLT2 inhibitors are stopped some days before because of euglycaemic ketoacidosis, and basal insulin is usually continued at a reduced amount by local protocol. Anticoagulants and antiplatelets are timed against the bleeding risk of the procedure and the clot risk of the patient, never stopped by reflex. The plan is written down, given to the patient, and includes when each medicine restarts.

Key points

• Usually continue: beta-blockers, statins, calcium channel blockers, inhalers, antiepileptics, thyroid replacement, antiparkinson drugs, antipsychotics and most antidepressants.
• Often held on the day: ACE inhibitors, angiotensin receptor blockers and diuretics (hypotension, low potassium and volume depletion).
• Diabetes: hold metformin and sulfonylureas while fasting, stop SGLT2 inhibitors days before, keep basal insulin at a reduced amount.
• Anticoagulants and antiplatelets: a plan agreed with the surgeon and, for stents or high clot risk, the cardiologist or haematologist.
• Ask about herbal products: several (ginkgo, garlic, ginseng) increase bleeding and St John's wort induces drug metabolism.

How it works

• Withdrawal syndromes: beta-blockers and clonidine rebound; antiparkinson drugs stopped suddenly cause rigidity and a neuroleptic malignant-like state.
• Interaction with anaesthesia: renin–angiotensin blockade removes a compensating pressor system once anaesthesia drops sympathetic tone.
• Fasting changes glucose: drugs that lower glucose without food (sulfonylureas, insulin) cause hypoglycaemia; SGLT2 inhibitors promote ketosis.
• GLP-1 receptor agonists slow gastric emptying, so a fasted stomach may still hold food; guidance varies and the anaesthetist weighs aspiration risk.
• Oestrogen-containing pills and hormone therapy raise venous thrombosis risk; some teams stop them about four weeks before major surgery with high clot risk.

Common classes and the usual plan (local protocols vary)

In practice

• Bring the actual boxes or a printed list: names, strengths and timing are checked against the record (medicine reconciliation).
• MAO inhibitors are usually continued with careful drug choice (avoid pethidine and indirect sympathomimetics); stopping them needs the psychiatrist.
• Lithium is often held before major surgery and restarted once eating and drinking with normal kidney function, with levels checked.
• A patient who took an ACE inhibitor that morning is not cancelled; the team expects hypotension and treats it.
• Write the restart plan: when each held medicine resumes is as important as when it stopped.

Next step

• Write a dated plan for every medicine (continue, hold from when, restart when) and give it to the patient in writing.
• Ask a senior or the specialist before stopping antiplatelets after a coronary stent, or anticoagulants with a mechanical valve or recent clot.
• On the day, check what was actually taken and when; a missed hold is managed, not hidden.
• After surgery, restart held medicines on the documented day and watch glucose, blood pressure and potassium.
• If surgery is delayed or cancelled, review the plan again rather than leaving medicines stopped.

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Elsewhere in DurgiPedia

• Preoperative care: assessment, teaching, fasting, skin preparation and the checklist

Connections

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Perioperative Anticoagulation Management (StatPearls (NCBI Bookshelf), 2023); Evaluation and Management of Perioperative Hypertension (StatPearls (NCBI Bookshelf), 2026).

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