Pre-operative Modification of Patient's
Drug Therapy
Aim To obtain best optimisation and stability peri-operatively
To ensure reversibility and quick control, change to drugs with shorter half lives To minimize withdrawal, side effects, and drug interactions To modify drug, dose, route and anaesthetic for best outcome
• Oestrogens (DVT risk) for 4 weeks pre and post surgery
(may continue if ambulatory, minor operations, or low dose) ACE inhibitors and angiotensin receptor inhibitors for 24 hours
• Clopidogrel for 7 days
Change • MAOI : pargyline, phenelzine, tranylcypromine, isocarboxacid Danger with pethidine, ephedrine (hypertension, fits, coma)
• Tri -cyclic anti-depressants block reuptake, cause tachyarrhythmias Danger with ephedrine, halothane, ketamine, and pancuronium
• Potassium sparing diuretics cause hyperkalaemia Danger with muscle injury, bums, renal disease, suxamethonium • Warfarin : stop for 3 days, convert to heparin, if needed
• Aspirin : stop for 7 days, but weigh risk / benefit (TURP high risk)
Continue. Beta blockers, Ca blockers, clonidine, to avoid hypertensive crises
• Anti-anginal therapy to prevent ischaemia
Bronchodilators to prevent bronchospasm
• Steroids to prevent adrenal crisis
• Anti epileptic therapy to avoid seizures
Caution Sympathomimetics cause hypertension, tachycardia, arrhythmias.
• Enzyme inhibitors (cimetidine) may prolong action of opiates, benzodiazepines, theophylline, LA, beta blockers, anti-coagulants.
• Enzyme inducers: Na valproate, barbiturates, phenytoin, carbamazepine
• Suxamethonium prolonged with ecothiopate, neostigmine, chemotherapy. • Non-depolarizers prolonged with aminoglycosides, Ca antagonists, Mg,
immunosuppressives, anti-arrhythmic drugs.
Amiodarone may cause 3rd degree heart block. • Diuretics causes hypovolaemia and hypokalaemia.
Lithium causes hypokalaemia. Digoxin toxicity with hypokalaemia • Anti-epileptics may have drug interactions due to enzyme induction.