Metformin 500mg Tablets
SUMMARY OF PRODUCT CHARACTERISTICS
1 NAME OF THE MEDICINAL PRODUCT
Metformin 500mg tablets
2 QUALITATIVE AND QUANTITATIVE COMPOSITION
One film-coated tablet contains:
Metformin hydrochloride 500 mg
3 PHARMACEUTICAL FORM
Film-coated tablets
White coloured, film-coated, round, biconvex tablets embossed ‘500’ on one side (without break score).
4 CLINICAL PARTICULARS
4.1 Therapeutic indications
- Non-insulin-dependent diabetes (NIDDM, type II) and, in particular, in obese patients, when adequate dietary treatment has failed.
- Metformin 500mg tablets can be given alone as initial therapy, or can be administered in combination with sulphonylureas after careful assessment of the contra-indications.
4.2. Posology and Method of Administration Posology
Adults and children over 12 years: Initially, 500mg every 8 hours or 850 mg every 12 hours, with or after food. Diabetic control may be achieved within a few days but the full effect can be delayed for up to 2 weeks. If control is incomplete, the dosage may be increased with care up to 2g and a maximum of 3g daily. Once adequate control has been achieved a reduction in dosage may be possible.
Children under 12 years: Not recommended
Elderly: Metformin should be used with caution in elderly patients whose renal function may be reduced.
In cases of metabolic decompensation:
The metformin dosage may be reduced in cases of metabolic decompensation. If only small daily doses are administered an omission of one metformin dose should be tried. This is of importance in elderly patients to reduce the risk of lactic acidosis.
Further dosage information
Combination with sulphonylureas:
Metformin 500mg tablets may be used in combination with sulphonylureas if monotherapy with metformin does not lead to a satisfactory response. However, it should be noted that metformin and sulphonylureas have a different mode of action and therefore an additive or potentiating effect of these drugs might cause a hypoglycaemic shock.
Substitution for sulphonylureas:
Metformin 500mg tablets may be used instead of sulphonylureas in patients who formerly have been treated with sulphonylureas.
Method of administration
For oral administration.
Monitoring advice
See special warnings and special precautions for use.
4.3 Contraindications
- In patients with non-insulin-dependent diabetes (NIDDM, Type II), if sulphonylurea therapy has completely failed
- Diabetic pre-coma, coma and ketoacidosis
- Hypersensitivity to metformin or any of the excipients
- Renal failure or impaired renal function of any degree
- Chronic liver disease or hepatic insufficiency
- Severe cardiovascular impairment
- Acute or chronic disease which may cause tissue hypoxia such as: Cardiac or respiratory failure, recent myocardial infarction, shock
- Severe peripheral vascular disease
- Acute conditions with the potential to alter renal function, for example infections with fever, pancreatitis or trauma
- Dehydration;shock
- History of or conditions associated with lactic acidosis such as shock or pulmonary insufficiency, alcoholism (acute or chronic), acute alcohol intoxication
- Reduced diet (< 1000kcal or 4,200kJ per day)
4.4 Special warnings and precautions for use
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. Lactic acidosis is characterised by acidotic dyspnea, abdominal pain and hypothermia followed by 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
Patients should be warned to consult a physician immediately if they suddenly suffer from these symptoms. On suspicion of lactic acidosis, metformin therapy must be immediately stopped and the patient treated at once as an emergency in hospital.
Metformin 500mg Tablets contain “propylene glycol” which may cause allergic reactions.
In patients with impaired liver function, lactate clearance may be restricted.
The risks of lactic acidosis and accumulation are determined by renal function. Therefore, metformin therapy requires normal renal function which should be monitored continuously, particularly in the elderly.
In elderly patients (approximately over the age of 65 years) metabolism is reduced and therefore a risk/benefit assessment should be carried out.
Surgery:
Metformin therapy should be stopped 48 hours before elective surgery under general, spinal or peridural anaesthesia and should not generally be resumed earlier than 48 hours afterwards and only after renal function has been reevaluated and found to be normal.
Renal function:
As 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 clearance level 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 antiinflammatory drug.
Administration of iodinated contrast agent:
Intravascular contrast studies with iodinated materials can lead to acute alteration of renal function and have been associated with lactic acidosis in patients receiving metformin. Therefore, in patients in whom any such studies are planned, metformin should be discontinued at the time of, or prior to, the procedure and withheld for 48 hours subsequent to the procedure and reinstituted only after renal function has been re-evaluated and found to be normal.
Children and adolescents
The diagnosis of type 2 diabetes mellitus should be confirmed before treatment with metformin is initiated. No effect of metformin and puberty has been detected during controlled clinical studies of one-year duratation 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 pre-pubescent children, is recommended.
Other precautions
During concomitant therapy with sulphonylureas or insulin, blood glucose levels should be monitored because combined therapy may cause hypoglycaemia.
Stabilisation of diabetic patients with metformin and insulin should be carried out in a hospital until the correct ratio of the two drugs has been obtained.
All patients should continue their diet with a regular distribution of carbohydrate intake during the day. Overweight patients should continue their energy-restricted diet.
Patients receiving continuous metformin therapy should have an annual estimation of Vitamin Bi2 levels because of reports of decreased Vitamin Bi2 or folic acid absorption which may cause megaloblastic anaemia. If necessary, Vitamin Bi2 should be given parenterally.
Serum creatinine levels should be determined before and four weeks after metformin therapy has been started. Regular measurements should take place once or twice a year unless required earlier due to intercurrent disorders. In elderly patients serum creatinine values often are not meaningful. Therefore, creatinine clearance should be tested before the onset of metformin therapy.
4.5. Interactions with other Medicaments and other forms of Interaction Contra-indicated
- Alcohol
• During treatment with Metformin 500mg tablets alcohol should be strictly avoided. Acute alcohol intoxication may enhance the hypoglycaemic effect and produce an increased risk of lactic acidosis particularly in case of fasting and malnutrition.
• Hepatic insufficiency
Avoid consumption of alcohol or alcohol-containing medicinal products.
- Iodinated contrast agents :
Intravascular administration of iodinated contrast agent 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 be 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 use
An increase of the antihyperglycaemic effect of metformin is possible in the event of concomitant administration with medicinal products for the same indication, for example:
- Insulin
- Oral antidiabetic drugs, of the sulphonylurea and acarbose type
An increase of the antihyperglycaemic effect of metformin is also possible in the event of concomitant administration with medicinal products for other indications which possess blood glucose-lowering effects of their own, for example:
- NSAIDs, e.g. salicylates or pyrazolones
- MAO inhibitors
- Oxytetracycline
- ACE inhibitors
- Clofibrate derivatives
- Cyclophosphamide and its derivatives
> The combination of metformin and the above-mentioned drugs can induce hypoglycaemia.
Moreover, during permanent therapy, beta-blockers and antisympathotonic drugs, such as clonidine, reserpine or guanethidine, may decrease blood glucose levels. However, of particular clinical relevance is their reducing action on the hormonal and neural counterregulation during hyperglycaemia, which in turn also impairs the subjective perception of hypoglycaemic warning signs.
A decrease of the antihyperglycaemic effect of metformin in combination with one of the following drugs may occur:
- Glucocorticoids(systemic or local route)
- Oestrogen-Progestagen-Combinations
- Adrenaline and other Sympathomimetics
- Glucagon
- Thyroid hormones
- Thiazides and loop diuretics. Diuretics especially loop diuretics, may increase the risk of lactic acidosis due to their potential to decrease renal function.
- Diazoxide
- Phenothiazines
- Nicotinic acid derivatives
More frequent blood glucose monitoring may be required, especially at the beginning of
treatment. If necessary, adjust the metformin dosage during the therapy with the respective medicinal products.
Guar: A decrease of the absorption of metformin may lead to an
attenuation of metformin effects.
Cimetidine: Substances which delay the elimination of metformin, e.g.
cimetidine, may increase the risk of lactic acidosis.
Phenprocoumone: Elimination of phenprocoumone and other coumarins may be accelerated during metformin therapy. Therefore the blood coagulation-inhibiting effect may be decreased and frequent controls of blood coagulation are necessary.
Iodinated contrast agents:
Intravascular administration of iodinated contrast agent 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 be
reinstituted until 48
Hours afterwards and only after renal function has been re- evaluated and
found to be normal.
To be taken into account
During maintenance therapy the onset or termination of any other additional
therapy can disturb the control of diabetes.
4.6. Pregnancy and Lactation
Pregnancy
Uncontrolled diabetes during pregnancy (gestational or permanent) is associated with increased risk of congenital abnormalities and perinatal mortality.
During pregnancy the administration of Metformin 500mg tablets is contraindicated. The treatment of diabetes mellitus should be adjusted with insulin during pregnancy or when pregnancy is desired. Animal studies have shown no particular effects with respect to reproduction and fertility. In man sufficient experience with metformin during pregnancy has not been obtained.
Use during lactation
The use of Metformin 500mg tablets should be avoided in women who are breast-feeding. Metformin 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, taken into account the benefit of breastfeeding and the potential risk to adverse effects on the child.
4.7. Effects on Ability to Drive and Use Machines
When used as monotherapy metformin does not cause hypoglycaemia and influence the ability to drive or operate machinery. In cases of combined therapy with sulphonylureas or other drugs (insulin or meglitinides), with blood glucose lowering effects, hypoglycaemia may occur and, hence, such combinations may produce minor or moderate adverse effects. Patients undergoing such combination therapy should be warned about the possible adverse effects of hypoglycaemia.
4.8 Undesirable effects
The following convention has been utilised for the classification of frequency: Very common,> 1/10; common, >1/100 and < 1/10; uncommon, >1/1000 and < 1/100; rare, > 1/10000 and < 1/1000; very rare, < 1/10000. , not known (cannot be estimated from the available data)
There are no modern clinical studies available that can be used to determine the frequency of undesirable effects.
Gastrointestinal disturbances occur in 5-20% of patients at the beginning of metformin therapy. These effects are generally of minor importance and do not require termination of metformin therapy. The frequency and severity can be reduced markedly by starting with a low dose and gradually increasing the dose and by administration of metformin with or after meals.
About 5% of all patients do not tolerate metformin therapy. Persisting gastrointestinal disturbances require the termination of metformin therapy.
Nervous System Disorders:
Common: Taste disturbance
Immune System Disorders:
Very rare: Hypersensitivity (including hypersensitivity reactions of the skin). Metabolism & Nutrition Disorders:
Very rare: megaloblastic anaemia due to decreased absorption of Vitamin B12 or folic acid (see Section 4.4); Lactic acidosis (symptoms include gastrointestinal disorders, muscle pains, muscle spasms, fatigue, dyspnoea, hyperthermia, hyperventilation, decrease of blood pH, increase of lactate value, clouding of consciousness and coma).
On suspicion of lactic acidosis, metformin therapy must be immediately stopped and the patient must be treated at once as an emergency in hospital.
Gastro-intestinal disorders:
Very common: nausea, vomiting, abdominal pain, diarrhoea, anorexia and metallic taste 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 be taken in 2 or 3 daily doses during or after meals. A slow increase of the dose may also improve gastrointestinal tolerability.
Hepatobiliary disorders:
Rare: liver function test abnormal; hepatitis resolving upon discontinuation of Metformin
Skin & Subcutaneous Tissue Disorders:
Very rare: erythema, pruritus, urticaria
Children and adolescents:
In published and post marketing data and in controlled clinical studies in a limited paediatric population aged 10 to 16 years treated during 1 year, adverse event reporting was similar in nature and severity to that reported in adults.
4.9. Overdose
Human experience
Intoxication with metformin does not lead to hypoglycaemia even at doses of up to 85 g but lactic acidosis may develop in such circumstances. Hypoglycaemia can occur when metformin is given concomitantly with sulphonylureas, alcohol or insulin.
Management of overdosage in man
In cases of metformin overdosage, for example in attempted suicide, or if signs of lactic acidosis are shown, patients must be admitted to a hospital as an emergency. The diagnosis of lactic acidosis should be confirmed by determination of lactate and metformin concentrations. Haemodialysis is the most effective measure to eliminate lactate and metformin. Symptomatic treatment includes circulatory stabilisation, compensation of acidosis and elimination of hypoxia. The metformin concentration in erythrocytes is a good indicator for accumulation and can be used to decide whether repeated haemodialysis is indicated.
5 PHARMACOLOGICAL PROPERTIES
5.1 Pharmacodynamic properties
Metformin is a biguanide oral antihyperglycaemic agent (ATC Code A10B A02) and reduces elevated blood glucose levels only in patients with non-insulin-dependent diabetes (NIDDM), but does not increase insulin secretion and does not cause hypoglycaemia or increased weight gain. Its mode of action is multifactorial and not yet completely understood. However, the augmentation of glucose uptake into peripheral tissues may influence glucose utilisation. Furthermore, the effects of metformin include reduced hepatic gluconeogenesis and delayed intestinal glucose absorption which may explain the blood glucose-lowering effect. The efficacy of metformin is dependent on a minimum concentration of insulin. A slight influence of the insulin secretion by metformin is possible but a clinical relevance is not very likely. Metformin seems to potentiate insulin action by enhancing insulin binding to its receptors and by facilitating steps in the post-receptor pathways of insulin-action. Apart from the glucose-lowering effect, metformin reduces the serum triglyceride level and possesses antithrombotic properties.
5.2. Pharmacokinetic Properties
After oral administration metformin is incompletely absorbed from the gastrointestinal tract. The oral bioavailability of usual doses is 50 - 60 %. The maximum plasma concentration is achieved after about 2 hours. Gastrointestinal absorption is complete within 6 hours of ingestion. The volume of distribution lies between 63 and 276 litres. Metformin is rapidly distributed but a slow transfer to a deep compartment seems to occur. Metformin does not bind to plasma proteins but accumulates in the salivary glands, duodenum, kidneys and liver. No metabolites or conjugates of metformin have been identified. Metformin is completely eliminated by renal excretion and the mean plasma elimination half-life ranges between 1.5 and
4.5 hours. A quantitatively minor terminal elimination phase, probably out of the deep compartment, with a longer mean half-life ranging from 8.9 to 19 hours, has been observed. The renal clearance of metformin ranges between 350 and 550 ml/min and correlates with the creatinine clearance, indicating that metformin is excreted by active tubular secretion. In patients with impaired renal function accumulation of metformin is probable.
5.3. Preclinical Safety Data
Acute toxicity:
Acute toxicity after different routes of administration and in different animals was investigated. The data indicate the highest toxicity of metformin hydrochloride after subcutaneous administration to guinea pigs and rabbits (LD50 = 150 mg/kg) and intravenous administration to mice (LD50 = 180 mg/kg). The toxicity after oral ingestion of metformin hydrochloride seems to be several times lower, rabbits and guinea pigs (LD50 3 5 0 and 500 mg/kg, respectively) being more sensitive than mice or rats (LD50 1 45 0 mg/kg and 1000 mg, respectively). Hence, in various animal species studied, after different routes of administration the LD50 values are considerably higher than the therapeutic dose range in humans (maximum approximately 40 mg/kg/day). The data indicate a low potential of acute toxicity.
Chronic toxicity:
Studies with repeated administration of metformin to rats (up to 18 months), dogs (up to 18 months) and monkeys (up to 2 years) revealed no specific toxic effects.
Mutagenic and carcinogenic effects:
Bacterial tests for mutagenicity of metformin were negative but chromosomal alterations were observed in vitro in mammalian cells. The relevance of these effects remains obscure. Long-term animal studies failed to detect any oncogenic properties of metformin.
Reproductive toxicity:
No teratogenic properties of metformin have been found in rats. The no adverse-effect level (NOAEL) of metformin in rats was estimated to be 300 mg/kg/day for embryotoxicity and female reproduction and up to 600 mg/kg/day for male fertility. No teratogenic effects were observed in rabbits with doses up to 140 mg/kg/day (p.o.). In rats doses up to 600 mg/kg/day administered p.o. pre- and postnatally showed no effects.
6 PHARMACEUTICAL PARTICULARS
6.1 List of excipients
Core
- Sodium starch glycollate
- Maize starch
- Povidone
- Colloidal anhydrous silica
- Magnesium stearate
Film-coating
- Hypromellose
- Titanium dioxide E 171
- Propylene glycol
- Macrogol 6000
- Purified talc
6.2. Incompatibilities
Not applicable.
6.3. Shelf Life
3 years
6.4. Special Precautions for Storage
Do not store above 25 °C.
6.5. Nature and Contents of Container
Blister pack of 28, 56 or 84 film-coated tablets (not all pack sizes may be marketed).
6.6. Instruction for Use/Handling
No special precautions are required.
7 MARKETING AUTHORISATION HOLDER
Auden Mckenzie Limited
Mckenzie House
Bury Street
Ruislip
Middlesex
HA4 7TL
United Kingdom
8 MARKETING AUTHORISATION NUMBER(S)
PL 17507/0007
DATE OF FIRST AUTHORISATION/RENEWAL OF THE AUTHORISATION
4 January 2001
10
DATE OF REVISION OF THE TEXT
18/07/2011