FACTORS INFLUENCING THE DESIGN OF CONTROLLED DRUG DELIVERY SYSTEM

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Submitted by on Wed, 10/03/2007 - 15:33.
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To establish criteria for the design of controlled release products, a number of variables must be considered mainly

1. Drug properties: The physicochemical properties of a drug, including stability, solubility, partitioning characteristic, charge and protein binding propensity play a dominant role in the design and performance of controlled release system.

2.Route of drug delivery: The area of the body in which drugs will be applied or administered can be restrictive on the basis of technological achievements of a suitable controlled release mechanism or device. Performance of controlled release systems may also be influenced by physiological constraints imposed by the particular route, such as first pass metabolism, gastrointestinal motility, blood supply and sequestration of small foreign particles by the liver and spleen.

3.Acute or chronic therapy: Consideration of whether one expects to achieve cure or control of a condition and the expected length of drug therapy are important factors in designing controlled release system. An attempt to generate a one-year contraceptive implant presents significantly different problems in design than does an antibiotic for acute infection. (Fara J. and Urquhart J. 1984).

4.The disease: Pathological changes during the course of a disease can play a significant role in the design of a suitable drug delivery system. Sometimes, one can take advantage of unique manifestation of disease state. For example, the higher plasminogen activator levels in some tumor cells can leads to preferential bioconversion of peptidyl prodrugs in these cells (Carl P.K. et al 1980, Chakravarty P.K. et al 1983, Weber M.J. et al 1983). Similarly, the higher tyrosinase level in melanoma cells has been demonstrated to allow targeting to and preferential bioconversion of 2,4-dihydroxyphenylalanine in them (Morrison M.E. et al 1985).

5.The patient: Whether the patient is ambulatory or bedridden, young or old, obese or gaunt etc. can influence the design of controlled release products. Some of these factors represent individual patient variation and cannot be controlled by the research scientist while others must be considered (Davis S.S. et al 1984).