When a drug is esterified into a bioconvertible prodrug ester and then formulated into an injectable form, it gives rise to esterification type depot preparation. This chemical approach depends upon the number of enzymes (esterases) present at the injection site, and the formulation forms a drug reservoir at the site of injection. The absorption rate of the drug is controlled by the interfacial partitioning of drug esters from the reservoir to the tissue fluid and the rate of bioconversion of drug esters to active drug molecules. Examples of this type of depot preparation are oleaginous injections of fluphenazine enanthate and nandrolone decanoate.

ADVANCES IN DELAYED RELEASE PARENTERAL DRUG DELIVERY SYSTEMS

Learning Objective

• Various types of parenteral controlled drug delivery systems