Question

Metformin (Glucophage) is an anti-diabetic medication with 60% bioavailbility and a biological half life of 7 hours. Apparent volume of distribution is 500 litres. A single OSD contains 500 mg of Metformin. Average Blood Plasma concentration levels at maintenance dosage are required to be 1.5mg/litre. Calculate the dosing regimen.

Answer 1

For the drug with long half lives, time to reach steady state might be long . It takes about five half lives to reach steady states.

In such cases the platue can be achieved by administering a dose that give desired steady state , such as initial / first dose is called loading dose.

Given , volume distribution = 500liter ,

. Bioavailability = 60% or 0.6 ,

target plasma concentrations =1.5mg/liter

, 500mg per tablet

BY FORMULA

Loading dose =

(plasma concentrations × volume distribution )÷ bioavailability

=( 1.5 mg /l × 500 liter )÷ 0.6

= 1250 mg

So ,. 1250 mg dose neede to achieve the 1.5mg /liter plasma concentrations of drug.

If, 500mg= 1tab

1250mg =X tab

X= 1250÷500 = 2.5

X= 2.5 tablets

We need to provide him. 2.5 tablets.

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