Bioavailability (BA) is the rate and extent to which the active ingredient from a pharmaceutical form is absorbed and reaches its site of action in the body. The key parameters used to measure the bioavailability of an orally administered drug are the "area under the plasma concentration-time curve (AUC)" and "maximum plasma drug concentration (Cmax)."

Bioequivalence (BE) refers to the similarity in the rate and extent of bioavailability, and thus therapeutic effects, between two different drug products that are pharmaceutically equivalent (for example, both are tablets/capsules) when given at the same molar dose.

According to current national and international guidelines, BE studies compare the bioavailabilities of two different drug products (test/generic/substitute product vs. reference/innovator/original product) in the same healthy volunteers, based on the Cmax and AUC ratios of the test/reference products. The first of these two parameters reflects the rate and extent of bioavailability, while the second reflects the extent of bioavailability. Since Cmax also indicates the maximum drug exposure the body experiences, it is important for reliability. Cmax and AUC are the "primary variables (parameters)" that form the basis for comparison in BE studies.

Bioequivalence studies are conducted in a limited number of healthy volunteers under controlled experimental conditions, comparing the bioavailability of the original drug with its equivalent. For this purpose, one drug is administered to the subjects, followed by a washout period, and then the other drug is administered—usually as a single dose orally. Plasma levels of the drugs are measured by drawing blood at specific intervals, typically over 24-48 hours.

(Due to the properties of the active ingredient and/or pharmaceutical form, some BE studies may be conducted in special designs: under fasting and fed conditions, with multiple doses, using urine samples, etc.). Using this data, the Cmax and AUC parameters of both drugs are compared. As a general rule, the trial drug is required to be 80-125% of the reference drug in terms of efficacy (within the confidence interval). If this condition is met, the bioequivalence of the newly produced drug (i.e., the generic drug) to the original drug is proven, and it is allowed to be marketed.

Bioavailability and Bioequivalence studies are conducted at the center. Since 2009, over 400 projects have been completed.