PHARMACOLOGY

 METHODS USED TO DELAY ABSORPTION OF DRUGS ::

1.Use of vasoconstrictors like adrenaline being added to a local anaesthetic like procaine to produce local action 

2.Reduction of surface area delays absorption due to poor blood supply 

3.Use of complex or insoluble salts of drugs e.g. plain insulin is quickly absorbed than its suspension lente insulin 

4.Use of oily or fatty base also delays the absorption of a drug from the parenteral site Adrenaline in oil or penicillin injection in peanut oil are common examples 

5.Implantation of DOCA (Deoxycorticosterone acetate ) testosterone or a progestin pellet of family planning under the skin renders the absorption very slow and steady for months and years 

6.Multilayered tablets are made such that the layers are absorbed slowly as desired The first layer in the acidic gastric juice and second in alkaline intestinal juice or an outer layer of a quick acting hypnotic followed by an inner layer of a long acting hypnotic which is double layered with clock like action 

7.Viscosity of the vehicle also matters The absorption of corticotrophin is slowled down if is dissolved in gelatin 

    Delay in absorption of drugs has distinct advantages for example insulin suspensions and lente procaine penicillin etc are absorbed slowly from the local site and hence maintain a sustained plasma concentration for a longer time Thus they decrease the number of pricks Multilayered tablets can be timed for their absorption and pointed action Skin implants also serve as a slowly leaking reservoir for months and years