Metformin If the patient is taking an oral hypoglycemic agent preoperatively the drug can be continued until the day of surgery, but sulfonylureas and nzetfornzin should not be used 24-48 h before surgery beause of their long half-lives. Patients with type 11 diabetes mellitus should be stopped oral hypoglycemics several days prior to surgery (especially metformin which is known to contribute to postoperative lactic acidosis) About other options Antihypeensive agents With rare exceptions antihypeensive drug therapy should be continued upto the time of surgery. Some clinicians withhold ACE inhibitors on the morning of surgery because of their association with an increased incidence of intraoperative hypotension. However withholding these agents increases the risk of marked perioperative hypeension and the need for parenteral antihypeensive agents. Surgical procedures on patients with sustained preoperative diastolic blood pressure higher than 110 mmHg-paicularly those with evidence of endorgan damage should be delayed until blood pressure is better controlled over the course of several days. Beta blockers A sudden stop can result in rebound hypeension, tachycardia and recurrent myocardial ischemia. They are continued up to and including morning of surgery and restaed immediately afterwards. Antianginal drugs Antianginal drugs such as calcium channel blockers or nitrates (GTN) should not be stopped before surgery without a very specific reason or angina may recur. Calcium channel blockers They have antiischaemic propey despite a theoretical risk of increased bleeding. They should be continued upto including the day of surgery. Nitrates To be continued up to and including day of surgery. About other classes of drugs Statins They should have a beneficial effect on outcome especially after coronary aery bypass grafting thus they are continued up to the day of surgery. Alpha 2 agonists Abrupt withdrawl an result in extreme hypeension and myocardial ischemia. So it should be continued upto and including the day of surgery. Diuretics There is risk of hypovolemia and hypotension but still should be continued up to the day of surgery. Digoxin and antiarryhthmics Should be continued upto the day of surgery. ACE inhibitors Continued use can result in perioperative hemodynamic instability For hypeension: continued to the day of surgery For hea failure: discontinue on the day of surgery especially if baseline blood pressure is low. Drugs that should be stopped before surgery Lithium It should be stopped 2 days before major surgery as it potentiates the non depolarizing group of relaxants and in emergency cases suxamethonium and regional blocks should be considered as alternative. Oestrogen containing oral contraceptive pills They are stopped before surgery beause they increase the risk of deep venous thrombosis. Surgery and the combined pill both reduce the activity of antithrombin Combined pills, should if possible be discontinued 4 weeks before major elective surgery or leg surgery such as varicose veins and staed again at the first period following an interval of 2 weeks after the operation. Aspirin Use may be associated with increased bleeding due to platelet dysfunction. They should be stopped 5-7 days before surgery if possible. Oral anticoagulants (warfarin) Should be stopped 4 days prior to surgery and substituted by iv heparin. Oral hypoglycemics Patients with type II diabetes mellitus should stop oral hypoglycemics several days prior to surgery (especially metformin which is known to contribute to postoperative lactic (acidosis) Patients on insulin (SC or iv) should omit their morning dose. Also know about these Monoamine oxidase inhibitors These drugs irreversibly inhibit monoamine oxidase. Stopping these drugs three weeks prior to anaesthesia to allow resynthesis of the enzyme is no longer considered necessary. Tricyclic antidepressants It competitively blocks norepinephrine reuptake by postganglionis sympathetic nerve endings. Patients taking these drugs are therefore more sensitive to catecholamines so any sympathominetic given simultaneously may cause hypeension and arryhthmia. These drugs were discontinued earlier but nowdays they are used.