PHARMACOLOGY

 SIGNIFICANCE OF BIOAVAILABILITY ::

The term bioavailability was intraduced by Oster (1945) It importance was realized especially in 1960s when there was an increase in number of generical prescriptions and formulations competition of different brands of the products repeal of anti -substitute laws and laws limiting or extending role of pharmacist in product selection in addition bioavailability gained significance in purchase of drugs based on the price 

        Theoretically bioavailability test is required for all drugs however it is practically not possible it has been recommended that bioavailability must be carried out for the following group of drugs : 

1.Drugs having low therapeutic index e.g. cardiac glycosides quinidine phenytoin etc 

2.Drugs whose peak levele are required for the effects of drugs e.g. phenytoin phenobarbitone primidone sodium valproate anti hypertensives antidiabetics and antibiotics 

3.Drugs that are absorbed by an active transport e.g. aminoacid analogues purine analogues etc 

4.Drugs which are disintegrated in the alimentary canal and liver e.g.chlorpromazine etc or those which under go first pass metabolism 

5.Formulations that give sustained release of drug formulations with smaller disintegration time than dissolution rate and drugs used as replacement therapy also warrant bioavailability testing in addition any new formulation has to be tested for its bioavailability profile