Clinical Tips: Bioequivalences with urinary data

Volunteers participating in clinical trials at our Quinta-Analytica clinical unit are sometimes surprised to discover that samples collected during the studies are not always blood or plasma but can also involve other biological fluids such as urine.

Ondřej Palán and Jitka Andršová from our Clinical Unit

The use of urine data is accepted as an alternative to plasma measurements whenever drug levels, time profiles and subject exposure cannot be reliably measured in blood. Urine measurements must be carefully justified when employed to estimate peak exposure: In bioequivalence studies with generic drugs, for example, it is necessary to scientifically determine that urinary excretion levels accurately mirror plasma exposure and thus serve as a reliable indicator of the behavior of the analyte in the body. Moreover, in those cases where maximum concentration (Cmax) can be determined in blood, it should complement urinary data for the estimation of extent of exposure in bioequivalence assessments.

We may also resort to urine samples when monitoring drugs that reach significant levels in urine, such as antibiotics for urinary tract infections (UTI). In those cases, the quantification of drug levels and their fluctuations in urine are fundamental parameters for determining bioequivalence between test and reference products.

We at Quinta-Analytica usually collect urine at one to four-hour intervals, and for volunteers this means that all urine produced during the day must be handed over to nurses and laboratory staff, who record collection time, volumes, homogenize and preserve samples for further analysis. Our clinical staff can manage full-day sampling for up to twenty-five subjects in parallel. Next, our bioanalytical team next door calculates concentrations of the monitored substances according to the total volume.

In conclusion, those not too fond of needles but interested in participating in a clinical trial should not feel excessively relieved, as they will still be required to have some blood samples taken but they will also have the chance to contribute to the development of new drugs for our society. Contact us at for more information about our clinical research activities.

Article by Tereza Korecká and Albert Pineda