PHARMACOLOGY

 TABLET DISINTEGRATION TIME ::

It is the time required for a tablet to disintergrate when placed in an appropriate solution 

TABLET DISSOLUTION RATE ::

It is the rate at which a drug goes into solution from its dosage form These methods although valid to some extent results obtained vary with these methods In short bioavailability describes the extent and the rate of drug absorption from a dosage form as reflected by the serum concentration -time curve This curve is obtained by plotting serum concentration of the drug versus time 

        Bioavailability of an oral dosage form is determined by comparing the Area Under the Curve (AUC) after oral administration of a single dose with that obtained when the same dose is given IV (100 Percent absorption ) : 

                    Drug bioavailability = AUC (Oral) 

                                                        ---------------*100

                                                        AUC(IV)

If all the drug that is absorbed is excreted unchanged in the urine then a similar determination can be carried out using the urine concentration versus time curve But if the drug is metabolized in the body as usually happens the metabolites as well as the parent drug must be measured The bioavailability can also be determined after chronic administration of a drug and there is usually good agreement between the results obtained by a single and multiple dose studies 

            The bioavailability is an important aspect of pharmacokinetics To determine pharmacokinetics three parameters are the most important -Biological -half life volume of distribution and Clearance other parameters are AUC Cmax (Maximum concentration achieved) Tmax (time to achieve maximum concentration) etc