- metformin hydrochloride
POM: Prescription only medicine
This information is intended for use by health professionals
Monotherapy and combination with other oral antidiabetic agents:• The usual starting dose is 500mg (5ml) or 850mg (8.5ml) 2 or 3 times daily given during or after meals.• After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increase of dose may improve gastrointestinal tolerability. The maximum recommended dose of metformin is 3000mg (30ml) daily, taken as 3 divided doses.• If transfer from another oral antidiabetic agent is intended; discontinue the other agent and initiate metformin at the dose indicated above.
Combination with insulin:• Metformin and insulin may be used in combination therapy to achieve better blood glucose control. Metformin is given at the usual starting dose of 500mg (5ml) or 850mg (8.5ml) 2-3 times daily, while insulin dosage is adjusted on the basis of blood glucose measurements.
Elderly:Due to the potential for decreased renal function in elderly subjects, the metformin dosage should be adjusted based on renal function. Regular assessment of renal function is necessary (see section 4.4).
Children and adolescents:
Monotherapy and combination with insulin• Metformin hydrochloride oral solution can be used in children from 10 years of age and adolescents.• The usual starting dose is 500mg (5ml) or 850mg (8.5ml) once daily, given during meals or after meals.• After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increase of dose may improve gastrointestinal tolerability. The maximum recommended dose of metformin is 2000mg (20ml) daily, taken as 2 or 3 divided doses.
Method of administrationThe required volume for each dose can be achieved with the dosing pipette.
|Lactic acidosis Lactic acidosis is a rare, but serious (high mortality in the absence of prompt treatment), metabolic complication that can occur due to metformin accumulation. Reported cases of lactic acidosis in patients on metformin have occurred primarily in diabetic patients with significant renal failure. The incidence of lactic acidosis can, and should, be reduced by also assessing other associated risk factors such as poorly controlled diabetes, ketosis, prolonged fasting, excessive alcohol intake, hepatic insufficiency and any condition associated with hypoxia.Diagnosis:The risk of lactic acidosis must be considered in the event of non-specific signs such as muscular cramps with digestive disorders, abdominal pain and severe asthenia.Lactic acidosis is characterised by acidotic dyspnoea, abdominal pain and hypothermia followed by coma. Diagnostic laboratory findings are decreased blood pH, plasma lactate levels above 5mmol/L, and an increased anion gap and lactate/pyruvate ratio. If metabolic acidosis is suspected, metformin should be discontinued and the patient should be hospitalised immediately (see section 4.9).|
Renal functionAs metformin is excreted by the kidney, creatinine clearance (this can be estimated from serum creatinine levels by using the Cockcroft-Gault formula) should be determined before initiating treatment and regularly thereafter:• at least annually in patients with normal renal function• at least two to four times a year in patients with creatinine levels at the lower limit of normal and in elderly subjects.Decreased renal function in elderly subjects is frequent and asymptomatic. Special caution should be exercised in situations where renal function may become impaired, for example when initiating antihypertensive therapy, diuretic therapy or when starting therapy with a non-steroidal anti-inflammatory drug (NSAID).
Administration of iodinated contrast agentsAs the intravascular administration of iodinated contrast agents in radiologic studies can lead to renal failure, metformin must be discontinued prior to, or at the time of the test and not be reinstituted until 48 hours afterwards, and only after renal function has been re-evaluated and found to be normal (see section 4.5).
SurgeryMetformin must be discontinued 48 hours before elective surgery under general, spinal or epidural anaesthesia. Therapy may be restarted no earlier than 48 hours following surgery or resumption of oral nutrition and only if normal renal function is established.
Children and adolescentsThe diagnosis of type 2 diabetes mellitus should be confirmed before treatment with metformin is initiated.No effect of metformin on growth and puberty has been detected during controlled clinical studies of one year duration but no long term data on these specific points are available. Therefore, a careful follow-up of the effect of metformin on these parameters in metformin-treated children, especially prepubescent children, is recommended.
Children aged between 10 and 12 years:Only 15 subjects aged between 10 and 12 years were included in the controlled clinical studies conducted in children and adolescents. Although efficacy and safety of metformin in these children did not differ from efficacy and safety in older children and adolescents, particular caution is recommended when prescribing to children aged between 10 and 12 years.
Other precautionsAll patients should continue their diet with a regular distribution of carbohydrate intake during the day. Overweight patients should continue their energy-restricted diet.The usual laboratory tests for diabetes monitoring should be performed regularly.Metformin alone does not cause hypoglycaemia, although caution is advised when it is used in combination with insulin or other oral antidiabetics (e.g sulphonylureas or meglitinides).This product contains:• Parahydroxybenzoates. These may cause allergic reactions (possibly delayed).• Liquid maltitol. Patients with rare hereditary problems of fructose intolerance should not take this medicine.• Sodium - 5.3 mg per 5 ml dose. This should be taken into consideration for patients on a controlled sodium diet.• Potassium - 14.5 mg per 5 ml dose. This should be taken into consideration for patients with reduced kidney function or patients on controlled potassium diets.
Concomitant use not recommended
AlcoholAcute alcohol intoxication is associated with an increased risk of lactic acidosis, particularly in cases of fasting or malnutrition or hepatic insufficiency. Consumption of alcohol and alcohol-containing medications should be avoided.
Iodinated contrast agents (see section 4.4)Intravascular administration of iodinated contrast agents may lead to renal failure, resulting in metformin accumulation and an increased risk of lactic acidosis. Metformin must be discontinued prior to, or at the time of the test and not reinstituted until 48 hours afterwards, and only after renal function has been re-evaluated and found to be normal (see section 4.4).
Combinations requiring precautions for useMedicinal products with intrinsic hyperglycaemic activity such as glucocorticoids (systemic or by local route) and sympathomimetics. More frequent blood glucose monitoring may be required, especially at the beginning of treatment. If necessary, adjust the metformin dosage during therapy with the respective medicinal product and upon its discontinuation.Diuretics, especially loop diuretics, may increase the risk of lactic acidosis due to their potential to decrease renal function.
PregnancyUncontrolled diabetes during pregnancy (gestational or permanent) is associated with increased risk of congenital abnormalities and perinatal mortality.A limited amount of data from the use of metformin in pregnant women does not indicate an increased risk of congenital abnormalities. Animal studies do not indicate harmful effects with respect to pregnancy, embryonal or foetal development, parturition or postnatal development (see section 5.3). When the patient plans to become pregnant, and during pregnancy, it is recommended that diabetes is not treated with metformin but insulin be used to maintain blood glucose levels as close to normal as possible to reduce the risk of malformations of the foetus.
BreastfeedingMetformin is excreted into human breast milk. No adverse effects were observed in breastfed newborns/infants. However, as only limited data are available, breastfeeding is not recommended during metformin treatment. A decision on whether to discontinue breast-feeding should be made taking into account the benefit of breast-feeding and the potential risk of adverse effects on the child
FertilityFertility of male or female rats was unaffected by metformin when administered at doses as high as 600 mg/kg/day, which is approximately three times the maximum recommended human daily dose based on body surface area comparisons.
Nervous system disorders:Common: Taste disturbance
Gastrointestinal disorders:Very common: Gastrointestinal disorders such as nausea, vomiting, diarrhoea, abdominal pain and loss of appetite. These undesirable effects occur most frequently during initiation of therapy and resolve spontaneously in most cases. To prevent them, it is recommended that metformin hydrochloride be taken in 2 or 3 daily doses during or after meals. A slow increase of the dose may also improve gastrointestinal tolerability.
Skin and subcutaneous tissue disorders:Very rare: Skin reactions such as erythema, pruritus, urticaria
Metabolism and nutrition disorders:Very rare: Lactic acidosis (see section 4.4).Decrease of vitamin B12 absorption with decrease of serum levels during long-term use of metformin hydrochloride. Consideration of such aetiology is recommended if a patient presents with megaloblastic anaemia.
Hepatobiliary disorders:Very rare: Isolated reports of liver function tests abnormalities or hepatitis resolving upon metformin hydrochloride discontinuation.
Paediatric populationIn published and post marketing data and in controlled clinical studies in a limited paediatric population aged 10-16 years treated during 1 year, adverse event reporting was similar in nature and severity to that reported in adults.
Reporting of suspected adverse reactionsReporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme: www.mhra.gov.uk/yellowcard.
Clinical efficacy:The prospective randomised (UKPDS) study has established the long-term benefit of intensive blood glucose control in adult patients with type 2 diabetes. Analysis of the results for overweight patients treated with metformin after failure of diet alone showed:• a significant reduction of the absolute risk of any diabetes-related complication in the metformin group (29.8 events/1000 patient-years) versus diet alone (43.3 events/1000 patient-years), p=0.0023, and versus the combined sulphonylurea and insulin monotherapy groups (40.1 events/1000 patient-years), p=0.0034;• a significant reduction of the absolute risk of diabetes-related mortality: metformin 7.5 events/1000 patient-years, diet alone 12.7 events/1000 patient-years, p=0.017;• a significant reduction of the absolute risk of overall mortality: metformin 13.5 events/1000 patient-years versus diet alone 20.6 events/1000 patient-years (p=0.011), and versus the combined sulphonylurea and insulin monotherapy groups 18.9 events/1000 patient-years (p=0.021);• a significant reduction in the absolute risk of myocardial infarction: metformin 11 events/1000 patient-years, diet alone 18 events/1000 patient-years (p=0.01).Benefit regarding clinical outcome has not been shown for metformin used as second-line therapy, in combination with a sulfonylurea.In type 1 diabetes, the combination of metformin and insulin has been used in selected patients, but the clinical benefit of this combination has not been formally established.
Paediatric populationControlled clinical studies in a limited paediatric population aged 10-16 years treated during 1 year demonstrated a similar response in glycaemic control to that seen in adults.
AbsorptionAfter an oral dose of metformin hydrochloride tablet, maximum plasma concentration (Cmax) is reached in approximately 2.5 hours (tmax). Absolute bioavailability of a 500 mg or 850 mg metformin hydrochloride tablet is approximately 50-60% in healthy subjects. After an oral dose, the non-absorbed fraction recovered in faeces was 20-30%.After oral administration, metformin absorption is saturable and incomplete. It is assumed that the pharmacokinetics of metformin absorption are non-linear.At the recommended metformin doses and dosing schedules, steady state plasma concentrations are reached within 24 to 48 hours and are generally less than 1 μg/ml. In controlled clinical trials, maximum metformin plasma levels (Cmax) did not exceed 5 μg/ml, even at maximum doses.Food decreases the extent, and slightly delays the absorption, of metformin. Following administration of a dose of 850 mg, a 40% lower plasma peak concentration, a 25% decrease in AUC (area under the curve) and a 35 minute prolongation of time to peak plasma concentration were observed. The clinical relevance of these findings is unknown.
DistributionPlasma protein binding is negligible. Metformin partitions into erythrocytes. The blood peak is lower than the plasma peak and appears at approximately the same time. The red blood cells most likely represent a secondary compartment of distribution. The mean volume of distribution (Vd) ranged between 63-276 L.
MetabolismMetformin is excreted unchanged in the urine. No metabolites have been identified in humans.
EliminationRenal clearance of metformin is > 400 ml/min, indicating that metformin is eliminated by glomerular filtration and tubular secretion. Following an oral dose, the apparent terminal elimination half-life is approximately 6.5 hours.When renal function is impaired, renal clearance is decreased in proportion to that of creatinine and thus the elimination half-life is prolonged, leading to increased levels of metformin in plasma.
Paediatric populationSingle dose study: After single doses of metformin hydrochloride 500 mg, paediatric patients have shown similar pharmacokinetic profile to that observed in healthy adults. Multiple dose study: Data are restricted to one study. After repeated doses of 500 mg twice daily for 7 days in paediatric patients the peak plasma concentration (Cmax) and systemic exposure (AUC0-t) were reduced by approximately 33% and 40%, respectively compared to diabetic adults who received repeated doses of 500 mg twice daily for 14 days. As the dose is individually titrated based on glycaemic control, this is of limited clinical relevance.
One Onslow Street, Guildford, Surrey, GU1 4YS
+44 (0) 1483 554831
+44 (0)1483 505 515
+44 (0)845 372 7101