Pharmacologic Evaluation of Bioavailability

The estimations of bioavailability discussed above are based on plasma and or urine levels of the drug and or its biotransformation products. It is understood in these calculations that these concentrations relate in some manner to the pharmacologic or clinical response of the drug. Ideally, therefore, it is desirable to measure bioavailability as a function of pharmacologic or clinical effect. In order to do so, a specific and discriminating test is needed. Some quantitative endpoint must be...

Subcutaneous Administration

The factors affecting intramuscular drug absorption also determine subcutaneous drug availability. The blood flow rates are poorer than in muscles and so are the rates of absorption. Yet some drugs are absorbed as rapidly from a subcutaneous site as from intramuscular administration, e.g., anionic dye, phenosulfonphthalein, and insulin. A prime determinant of the absorption rate of a subcutaneous depot is the total surface area over which the absorption can occur. Although the subcutaneous...

Pulmonary Administration

Drugs can be introduced into the pulmonary system as gases or in aerosol forms. An almost instantaneous absorption can be expected due to the extremely large surface area available for absorption. The primary mechanism of absorption is passive diffusion but the lipid solubility tends to play a smaller role than in gastrointestinal absorption. The main limiting step in the utilization of this route has been the need to design dosage forms which accurately deliver the drugs. Most of these drugs...