Choosing the right primary packaging is one of the most important steps in drug development. Its role is to assure drug efficacy through the intended shelf life while protecting it from all adverse external influences that can change its properties, an important one being moisture. Radio-frequency identification (RFID) method offers a nondestructive way of measuring internal changes of relative humidity directly in the primary packaging - in our case inside a blister cavity. In this thesis, we explore the capabilities of the RFID method to quantify the water vapor transmission rate and compare the results with the USP <671> method.
We tested PVC 250, PVC/PVDC 200/60, PVC/PVDC 250/120, PVC/PE/PVDC 250/25/180 and PVC/Aclar® 254/76 formed in round blister cavity sizes of 9x5 mm, 10x5 mm, 11x6 mm, 13x5 mm and 15x6 mm. These configurations were exposed to climate conditions of 30°C/75% RH, 40°C/75% RH and 50°C/75% RH. Each configuration was represented with 4 RFID transponders, out of which a third was calibrated by the Microsensys company. With this method we noticed statistically significant changes of RH after the blistering procedure.
Through a fit of experimental relative humidity measurements, we extracted the time constant. We compared the results between polymer films used and determined that PVC 250 has the worst water vapor barrier, whereas PVC/PE/PVDC 250/25/180 and PVC/Aclar® 254/76 the best. Size 9x5 mm expectedly had the highest time constant and size 15x6 mm the lowest. Interestingly, the time constant was second highest with 13x5 mm followed by 10x5 mm, whereas 11x6 mm had the second lowest. The time constants decreased with increasing temperature, as expected. All RFID results were compared to the results of the USP <671> method and showed similar difference ratios in these comparisons. Subsequently we tried to calculate the water vapor transmission rate through the extracted time constant. This was not achieved, due to the unknowing wall thicknesses of the blister cavities and the model not being complex enough to take this into account.
In summary, our results show that RFID method can be used as a supplement to the stability studies. With additional experimentation and improvements to the model it has the potential to become the method of choice for selection of primary packaging.