Repaglinide and Metformin

Uses

Repaglinide is used for an adjunct to diet and exercise to lower the blood glucose level in patients with type 2 diabetes mellitus (NIDDM) whose hyperglycaemia cannot be controlled satisfactorily by diet and exercise alone. It is also used for use in combination with Metformin to lower blood glucose in patients whose hyperglycaemia cannot be controlled by exercise, diet, and either Repaglinide or Metformin alone. Repaglinide binds to specific receptors in the cell membrane leading to the closure of ATP dependent K+ channels and the depolarisation of cell membrane. This in turn, leads to Ca++ influx, increased intracellular Ca++ and the stimulation of insulin secretion.

Repaglinide and Metformin is also used to associated treatment for these conditions: Type 2 Diabetes Mellitus

How Repaglinide and Metformin works

Repaglinide activity is dependent on the presence functioning β cells and glucose. In contrast to sulfonylurea insulin secretatogogues, repaglinide has no effect on insulin release in the absence of glucose. Rather, it potentiates the effect of extracellular glucose on ATP-sensitive potassium channel and has little effect on insulin levels between meals and overnight. As such, repaglinide is more effective at reducing postprandial blood glucose levels than fasting blood glucose levels and requires a longer duration of therapy (approximately one month) before decreases in fasting blood glucose are observed. The insulinotropic effects of repaglinide are highest at intermediate glucose levels (3 to 10 mmol/L) and it does not increase insulin release already stimulated by high glucose concentrations (greater than 15 mmol/L). Repaglinide appears to be selective for pancreatic β cells and does not appear to affect skeletal or cardiac muscle or thyroid tissue.

Dosage

Repaglinide and Metformin dosage

Repaglinide has to be taken just before or up to 30 minutes before the meal. Repaglinide can be taken two, three or four times a day, depending on how many meals are taken. If a meal is missed, Repaglinide should also be avoided. If an extra meal is taken, an extra dose of Repaglinide should be taken with that meal. If a dose of Repaglinide is missed, it should not be taken between meals.

Rather the usual dose should be taken before the next meal. The dose ranges from 0.5 to 4 mg before each meal. The starting dose of Repaglinide in patients with HbA1c <8% is 0.5 mg before each meal. In patients with HbA1c >8% the starting dose is 1 or 2 mg before each meal. The dose may be increased gradually up to 4 mg before each meal.

Side Effects

Hypoglycaemia is possible with all blood glucose lowering drugs. If there are symptoms of low blood glucose (for example, headache, dizziness, tiredness, nervousness or shakiness, rapid heartbeat, or nausea), blood glucose should be tested right away. If it is low (less than 70 mg/dl on a home glucose meter), a simple carbohydrate food (for example, orange juice, quick dissolving sugar, candies, or glucose tablets) should be taken. If the symptoms do not go away, doctor should be informed. Some of the other common symptoms reported by patients taking Repaglinide include cold and flu-like symptoms, diarrhoea, joint ache, and back pain. There is some evidence that oral anti-diabetic drugs may increase the risk of heart problems. But experts are not sure what the real risk is, if any, from taking oral anti-diabetic drugs.

Toxicity

LD₅₀ >1 g/kg (rat) (W. Grell)

Precaution

Repaglinide should also be used with caution in renal and hepatic insufficiency.

Interaction

The dose of Repaglinide may need to be adjusted, if taken with other medications. The possible interactions of Repaglinide with other drugs are:

• Inhibitors of the cytochrome P450 enzyme system (azole antifungals and macrolides) may lead to lower Repaglinide clearance and longer half life.
• Inducers of the cytochrome P450 enzyme system (Rifampin, Phenobarbital, Carbamazepine, Troglitazone, etc.) may accelerate Repaglinide metabolism and shorten its effect.
• Cimetidine has no significant effect on Repaglinide absorption or clearance.
• Repaglinide has no significant effect on Digoxin, Theophyllin, or Warfarin.
• Highly protein bound drugs (e.g., NSAIDs) may increase the plasma level of unbound Repaglinide and potentiate its glucose lowering effect. Thus, co-administration of these drugs with Repaglinide may increase the risk of hypoglycaemia.
• The risk of hypoglycaemia may also be increased when hypoglycaemic agents are co-administered with certain drugs such as salicylates, sulphonamides, Chloramphenicol, coumarins, Probenecid, monoamine oxidase (MAO) inhibitors, and adrenergic blockers.

Volume of Distribution

31 L following IV administration in healthy individuals

Elimination Route

Rapidly and completely absorbed following oral administration. Peak plasma concentrations are observed within 1 hour (range 0.5-1.4 hours). The absolute bioavailability is approximately 56%. Maximal biological effect is observed within 3-3.5 hours and plasma insulin levels remain elevated for 4-6 hours. When a single 2 mg dose of repaglinide is given to healthy subjects, the area under the curve (AUC) is 18.0 - 18.7 (ng/mL/h)^3.

Half Life

1 hour

Clearance

33-38 L/hour following IV administration

Elimination Route

90% eliminated in feces (<2% as unchanged drug), 8% in urine (0.1% as unchanged drug)

Pregnancy & Breastfeeding use

In pregnancy, safety of Repaglinide has not been established. Hence, Repaglinide should be used during pregnancy only if it is clearly needed. It is not known whether Repaglinide is excreted in human milk. Because many drugs are excreted in human milk and because of potential for serious adverse reactions in nursing infants from Repaglinide, a decision should be made whether to discontinue nursing or the drug, taking into account the importance of the drug to the mother.

Contraindication

Repaglinide is contraindicated in patients with diabetic ketoacidosis, with or without coma, in patients with type I diabetes and in patients with known hypersensitivity to any of the components of the product.

Acute Overdose

Patients receiving up to 80 mg of Repaglinide developed few adverse effects other than lowering of blood glucose. Hypoglycemia did not occur when meals were given with these high doses. Severe hypoglycemic reactions with coma, seizure or other neurological impairment occur infrequently.

Storage Condition

Store below 25° C. Protect from moisture.

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