Metformin (Biguanides)

Introduction

Metformin is the only available drug in this class and it has a different mode of action from the Sulphonylureas, and it is not interchangeable with them. Metformin is the drug of first choice in overweight patients in whom strict dieting has failed to control diabetes.

Mechanism of action

This is very complex and incompletely understood

Mode of actions

1. it increases the peripheral sensitivity for insulin by;

I. increasing glucose uptake and utilization by skeleton muscles
II. reducing insulin resistance

2. it reduces LDL and VLDL level
3. It increase HDL level

Pharmacokinetics

Oral bio-availability is 50-60%.The half life of metformin is about 3 hours. It is excreted via urine as it is.

Adverse drug reactions

1. Dose related gastrointestinal disturbances(anorexia, diarrhea, nausea)
2. It can cause lactic acidosis. Even though this is rare it can be fatal. Therefore Metformin should not be given to patients with renal/ hepatic disease, hypoxic pulmonary disease, heart failure or shock.
3. Long term use may interfere with vitamin B12 absorption.
4. teratogenic

Clinical uses

1. Start with smaller doses and gradually increase the dose to over come the adverse effects.
2. given immediately after the meal
3. Drug of choice for patients with type2 DM and obesity.
4. can be combined with Sulphonylureas, Glitazones or insulin
5. does not cause hypoglycemia
6. preserved for middle and old age patients