Drug Delivery Systems

Ajinkya Shitole (SIU-JRF)

Drug delivery is the method of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. A suitable amount of the active drug must be absorbed and transported to the site of action at the right time and in right concentrations (therapeutic range). There are various routes of Drug delivery such as oral, parenteral which includes intramuscular, intravenous, intra-arterial and subcutaneous route, transdermal and Inhalation route. Several drug delivery systems have been formulated and tested for these routes to obtain a desired therapeutic response.

The most critical points in drug delivery are the improvement of drug efficacy and safety. Conventional, drug delivery system have its own limitations which is high concentrations of drug post administration followed by sudden decline which is much below the required therapeutic level. So currently the need of the hour is targeted therapy; such that the drug should reach its intended site of action evading host’s defense mechanism. One of the leading strategies to do so is through development of novel drug delivery systems (DDS). This strategy is based on interdisciplinary approach that combines Polymer science, Pharmaceutics, Chemistry and Molecular biology.

Novel drug delivery systems include those based on Physical mechanism and those based on Biochemical mechanism. Physical mechanism also referred to as controlled delivery systems include: Osmosis, Diffusion, Erosion, Dissolution, and Electro Transport. Biochemical mechanism includes: Monoclonal antibodies, gene therapy and vector systems, polymer drug adducts and liposomes.  Nanoparticles are another such delivery system which is composed of biodegradable polymers which fulfill the properties required for such delivery systems such as ability to be transferred into an aerosol, stability against forces generated during aerosolization, biocompatibility, targeting at specific sites, release of the drug in a predetermined manner, and degradation within an acceptable period of time.

Several pharmaceutical companies are developing drug delivery system in India and are being tested for their in vitro release pattern and in some cases in vivo in animals for pharmacokinetics. However they are less frequently tested for efficacy. Thus there exist a paucity of data as far as their clinical validation and application in patient is concerned. Hence it is necessary that pharmacologists should be involved in the investigation of pharmacokinetics and pharmacodynamics of DDS to understand the exact utility of DDS i.e. if the products have reached their meaningful outcome (clinical use).