Measuring the viscosity of pharmaceutical dosage forms is a crucial process. Viscosity
provides information about the stability of the composition, the release rate of the
drug, bioavailability, and, in the case of injectable drug formulations, even the
force required for injection. However, measuring viscosity is a complex task with
numerous challenges, especially for non-Newtonian materials, which include most pharmaceutical
formulations, such as gels. Selecting the appropriate shear rate is critical. Since
viscosity in many systems is highly temperature-dependent, stable temperature control
is necessary during the measurement. Using microfluidics technology, it is now possible
to perform rheological characterization and conduct fast and accurate measurements.
Small sample volumes (even below 500 µL) are required, and viscosity determination
can be carried out over a wide range of shear rates. Nevertheless, the pharmaceutical
application of viscometers operating on the principle of microfluidics is not yet
widespread. In our work, we compare the results of measurements taken with a microfluidic
chip-based viscometer on different pharmaceutical forms (gels, solution) with those
obtained using a traditional rotational viscometer, evaluating the relative advantages
and disadvantages of the different methods. The microfluidics-based method enables
time- and sample-efficient viscosity analysis of the examined pharmaceutical forms.
