- metformin hydrochloride
POM: Prescription only medicine
This information is intended for use by health professionals
Monotherapy and combination with other oral antidiabetic agents: Glucient SR 1000 mg should be taken once daily with the evening meal at a maximum recommended dose of 2 tablets per day. Glucient SR 1000 mg is intended as a maintenance therapy for patients currently treated with either 1000 mg or 2000 mg of metformin hydrochloride. On switch, the daily dose of Glucient SR should be equivalent to the current daily dose of metformin hydrochloride. In patients treated with metformin hydrochloride at a dose above 2000 mg daily, switching to Glucient SR is not recommended. For patients new to metformin hydrochloride, the usual starting dose of Glucient SR is 500 mg once daily given with the evening meal. After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increment in dose may improve gastrointestinal tolerability. If glycaemic control is not achieved on once daily dosing of Glucient SR at a maximum dose of 2000 mg a day, then a twice daily dosing schedule should be considered with both doses being given with food, at the time of the morning and evening meals. If glycaemic control is still not achieved, patients may be switched to standard metformin hydrochloride tablets to a maximum dose of 3000 mg daily. In the event of transfer from another oral antidiabetic agent, titration should begin with Glucient SR 500 mg before switching to Glucient SR 1000 mg as indicated above.
Combination with insulin:Metformin hydrochloride and insulin may be used in combination therapy to achieve better blood glucose control. The usual starting dose of Glucient SR is 500 mg once daily with the evening meal, while insulin dosage is adjusted on the basis of blood glucose measurements. After titration, switch to Glucient SR 1000 mg should be considered.
Elderly:Due to the potential for decreased renal function in elderly subjects, the metformin hydrochloride dosage should be adjusted based on renal function. Regular assessment of renal function is necessary (see section 4.4).Children:In the absence of available data, Glucient SR should not be used in children.
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 assessing also 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 muscle cramps with digestive disorders as abdominal pain and severe asthenia.This can be followed by acidotic dyspnea, abdominal pain, hypothermia and coma.Diagnostic laboratory findings are decreased blood pH, plasma lactate levels above 5 mmol/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 function:As metformin is excreted by the kidney, creatinine clearance (this can be estimated from serum creatinine levels 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 clearance levels at the 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 or diuretic therapy and when starting therapy with an non-steroidal anti- inflammatory drug (NSAID).
Administration of iodinated contrast media:The intravascular administration of iodinated contrast media in radiological studies can lead to renal failure. This may lead to metformin accumulation and 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 reevaluated and found to be normal (see section 4.5).
Surgery:Metformin should be discontinued 48 hours before elective surgery with general spinal or peridural anaesthesia. Therapy may be restarted no earlier than 48 hours following surgery or resumption of oral nutrition provided normal renal function has been established.Other precautions:All 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 never causes hypoglycaemia, although caution is advised when it is used in combination with insulin or other oral antidiabetics (e.g. sulphonylureas or meglitinides).The tablet shells may be present in the faeces. Patients should be advised that this is normal.
ExcipientsEach tablet contains up to 20.7mg sodium (1.0 mmol) which should be taken into consideration for patients on a controlled sodium diet.
Concomitant use not recommended
AlcoholAcute alcohol intoxication is associated with an increased risk of lactic acidosis in acute alcohol intoxication, particularly in case of: fasting or malnutrition, hepatic insufficiency.Avoid consumption of alcohol and alcohol-containing medications.
Iodinated contrast mediaIntravascular administration of iodinated contrast media may lead to renal failure, resulting in metformin accumulation and a risk of lactic acidosis. Metformin hydrochloride 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 reevaluated and found to be normal (see section 4.4).
Combinations requiring precautions for useMedicinal products with intrinsic hyperglycaemic activity (e.g. glucocorticoids (systemic and local routes) 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 other drug and upon its discontinuation.
Diuretics, especially loop diuretics
They 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, embryonic or fetal 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 fetus.
LactationMetformin is excreted into human breast milk. No adverse effects were observed in breastfed newborns/infants. However, as only limited data are available, breast-feeding 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.
|Metabolism and nutrition disorders|
|Very rare:||Lactic acidosis (see 4.4. Special warnings and precautions for use). Decrease of vitamin B12 absorption with decrease of serum levels during long- term use of metformin. Consideration of such an aetiology is recommended if a patient presents with megaloblastic anaemia.|
|Nervous system 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. A slow increase of the dose may also improve gastrointestinal tolerability.|
|Isolated reports:||Liver function tests abnormalities or hepatitis resolving upon metformin discontinuation.|
|Skin and subcutaneous tissue disorders|
|Very rare:||Skin reactions such as erythema, pruritus, urticaria|
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 at: www.mhra.gov.uk/yellowcard.
Clinical efficacy:The prospective randomised (UKPDS) study has established the long-term benefit of intensive blood glucose control in overweight type 2 diabetic patients treated with immediate release metformin hydrochloride as first-line therapy after diet failure.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)For metformin used as second-line therapy, in combination with a sulphonylurea, benefit regarding clinical outcome has not been shown.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.
AbsorptionAfter an oral dose of the prolonged release tablet, metformin absorption is significantly delayed compared to the immediate release tablet with a reported Tmax at approximately 7 hours (Tmax for the immediate release tablet is 2.5 hours).At steady state, similar to the immediate release formulation, Cmax and AUC are not proportionally increased to the administered dose. The AUC after a single oral administration of 2000 mg of metformin prolonged release tablets is similar to that observed after administration of 1000 mg of metformin immediate release tablets b.i.d.Intrasubject variability of Cmax and AUC of metformin prolonged release is comparable to that observed with metformin immediate release tablets.No accumulation is observed after repeated administration of up to 2000 mg of metformin as prolonged release tablets.Following a single oral administration of one tablet of Glucient SR 1000 mg under fasting conditions, mean AUC of 10927 ng.hr/ml and a mean peak plasma concentration of 1488 ng/ml is achieved 4 hours (range 2 to 6.5 hours) after administration.Following a single oral administration of one tablet of Glucient SR 1000 mg under fed conditions, mean AUC of 15577 ng.hr/ml and a mean peak plasma concentration of 1397 ng/ml is achieved 6.5 hours (range of 3.5 to 12 hours) after administration.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.