Adult: Treatment: As conventional tab/solution: Initially, 500 or 850 mg bid or tid, gradually increase at intervals of at least 1 week according to response. Max: 3,000 mg daily in 3 divided doses. As extended-release tab: Initially, 500 mg daily with evening meal, increase dose in increments of 500 mg up to Max 2,000 mg daily according to response. Prophylaxis: As extended-release tab: Initially, 500 mg daily with evening meal, gradually increase dose at intervals of 10-15 days, according to response. Max: 2,000 mg daily with evening meal. Child: ≥10 years As conventional tab/solution: Initially, 500 or 850 mg once daily, gradually increase dose at intervals of at least 1 week according to response. Max: 2,000 mg daily in 2 or 3 divided doses. Elderly: Adjust dose based on renal function.
eGFR <30 mL/min: Contraindicated. eGFR 30-44 mL/min: Total Max daily dose: 1,000 mg. eGFR 45-59 mL/min: Total Max daily dose: 2,000 mg daily. eGFR 60-89 mL/min: Total Max daily dose: 3,000 mg. All doses to be taken in 2-3 divided doses.
Should be taken with food.
Acute or chronic metabolic acidosis with or without coma, acute conditions which may alter renal function (e.g. dehydration, severe infection, shock), acute or chronic disease-causing hypoxia (e.g. unstable cardiac or respiratory failure, recent MI, shock), acute alcohol intoxication or alcoholism. Severe renal (eGFR<30 mL/min) impairment. Intravascular administration of iodinated contrast agents.
Patients with risk factors for lactic acidosis, stable heart failure, dehydration, prerenal azotemia. Mild to moderate renal impairment. Hepatic impairment. Children and elderly. Pregnancy and lactation. Not indicated for use in patient with type 1 diabetes mellitus or with diabetic ketoacidosis.
Monitor glucose and ketones (urine and blood), fasting blood sugar, haemoglobin A1c at least twice yearly in stable glycaemic control; quarterly if not meeting therapy goals. Monitor renal function prior to initiation of therapy and annually thereafter; haematologic parameters at baseline and annually thereafter; vitamin B12 serum concentration every 2-3 years (prolonged use). Monitor for signs and symptoms of lactic acidosis.
Symptoms: Hypoglycaemia, lactic acidosis manifested as acidotic dyspnoea, abdominal pain, muscle cramps, hypothermia followed by coma. Management: Perform haemodialysis to remove lactate and metformin in the blood.
Increased risk of hypoglycaemia with insulin and insulin secretagogues (e.g. sulfonylurea). Increased risk of lactic acidosis with carbonic anhydrase inhibitors (e.g. acetazolamide, dichlorphenamide), NSAIDs, and antihypertensive agents (e.g. ACE inhibitors). Increased plasma concentration and reduced clearance with OCT2 inhibitors (e.g. cimetidine, dolutegravir, ranolazine, trimethoprim, vandetanib, isavuconazole). Potentially Fatal: Contrast-induced nephropathy and increased risk of lactic acidosis with iodinated contrast agents.
Food decreases extent and slightly delays absorption. Increased risk of lactic acidosis with alcohol.
Description: Metformin is a biguanide antihyperglycaemic agent which improves glucose tolerance by lowering both basal and postprandial plasma glucose. It decreases hepatic glucose production by inhibiting gluconeogenesis and glycogenolysis, delays intestinal glucose absorption, and improves insulin sensitivity by enhancing peripheral glucose uptake and utilisation. Onset: Within days. Pharmacokinetics: Absorption: Slowly and incompletely absorbed from the gastrointestinal tract. Food decreases extent and slightly delays absorption. Absolute bioavailability: 50-60% (fasting); reduced if taken with food. Time to peak plasma concentration: 2-3 hours (immediate-release); 7 hours, range: 4-8 hours (extended-release). Distribution: Distributes and concentrates in liver, kidney and gastrointestinal tract; partitions into erythrocytes. Crosses placenta and enters breastmilk. Volume of distribution: 654 ± 358 L. Plasma protein binding: Negligible. Metabolism: Not metabolised. Excretion: Via urine (approx 90% as unchanged drug). Elimination half-life: 6.2 hours (plasma); approx 17.6 hours (blood).
Store below 30°C. Protect from light and moisture.
A10BA02 - metformin ; Belongs to the class of biguanides. Used in the treatment of diabetes.
Anon. Metformin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 17/05/2019.Buckingham R (ed). Metformin Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 17/05/2019.Joint Formulary Committee. Metformin Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 16/09/2014.McEvoy GK, Snow EK, Miller J et al (eds). Metformin Hydrochloride. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 16/09/2014.Metformin Extended-Release Tablet (Qingdao Baheal Pharmaceutical Co., Ltd.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/05/2019.Metformin Solution (Innovida Pharmaceutique Corporation). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/05/2019.Metformin Tablet (ScieGen Pharmaceuticals Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/05/2019.