ABSTRACT

The objective of drug therapy is to produce and maintain a therapeutic response while minimizing undesirable and/or toxic effects. This chapter presents an overview of the biopharmaceutical principles involved in the administration and absorption of drugs. Drugs are distributed throughout the body in the water phase of the blood plasma, regardless of their site of entry. Some of the drug molecules may be bound to proteins in the blood plasma and thus may not be freely diffusible out of the plasma. Drug solubility is the mass of drug that can be dissolved per unit volume of solvent. Some drugs exist in a number of crystal forms or polymorphs. These different forms may well have different solubility properties and thus different dissolution characteristics. The therapeutic efficacy of a dosage form may be affected by the particle size. The role of wetting agents is to separate the small particles of drug and facilitate wetting during disintegration of oral dosage forms.