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Category Archives: Biopharmaceutics

Pharmacokinetics – Distribution Series II – Rate of Drug Distribution


Figure 4.1 shows the plasma concentration and the typical tissue concentration profile after the administration of a drug by intravenous injection. It can be seen that during the distribution phase, the tissue concentration increases as the drug distributes to the tissue. Eventually, a type of equilibrium is reached, and following this, in the postdistribution phase, […]

Extended-Release Drug Products


Most conventional (immediate release) oral drug products, such as tablets and capsules, are  formulated to release the active drug immediately after oral administration. In the formulation of conventional drug products, no deliberate efforts is made to modify the drug release rate. Immediate-release products generally result in relatively rapid drug absorption and onset of accompanying pharmacodynamic […]

Drug Absorption in the Gastrointestinal Tract


Rate-Limiting Steps in Drug Absorption Disintegration of the drug product and subsequent release of the drug (rate-limiting step) Dissolution of the drug in an aqueous environment (rate-limiting step) Absorption across the cell membranes into the systemic circulation (rate-limiting step) Physiochemical Factors that Affect Drug Absorption Drug disintegration (rate-limiting step) Drug dissolution (rate-limiting step) Drug across the cell […]