Chemical Delivery Systems (Polymeric Prodrugs)

Properties of Polymeric Prodrugs
1- Prolongation of Action of the Drug
The profile of plasma concentration of drugs is an important determinant of their quantitative access to peripheral targets. The plasma profile is usually measured as the area under the curve (AUC).
In general, slow renal elimination and metabolic inactivation promote better access of drugs to remote targets, although this can also cause elevated toxicity.
Many drugs in routine use are membrane permeable because their sites of action are intracellular and such drugs typically exhibit high volumes of distribution and rapid plasma clearance.
By linking a drug onto a polymer, a conjugate is obtained with a higher hydrodynamic volume. This results in a slower renal excretion, longer blood circulation and an endocytotic cell uptake

To select polymers as candidate drug carriers a number of requirements should be fulfilled:
1.Availability of suitable functional groups for covalent coupling with drugs.
2.Biocompatibility: preferably nontoxic, nonimmunogenic.
3.Biodegradability or a molecular weight below the renal excretion limit.
4.Availability. Along with the polymer, the physico-chemical properties of the drug or biomolecule to be conjugated are equally important. The following properties of the drug molecules make it suitable as an ideal candidate to form the polymeric conjugate:
1.Lower aqueous solubility.
2.Instability at varied physiological pHs.
3.Higher systemic toxicity.
4.Reduced cellular entry