How suitable is the measurement of take-off forces for detection of sticking during direct compression of various ibuprofen tablet formulations?

Sticking of tablet formulations to punch surfaces is one of the most common problems observed during tablet manufacture. An inline method proposed for detection of sticking during compression is the measurement of take-off forces, which occur when tablets are detached from the lower punch surface. It has been postulated that the tablet take-off force is a direct indicator of the sticking tendency of a tablet formulation. In the present study, the take-off forces measured during direct compression of sticking ibuprofen tablet formulations were evaluated and compared to the sticking extent of these tablets quantified by HPLC analysis of ibuprofen. As expected, sticking to the lower punch was increased with an increase of the ibuprofen content in the investigated tablet formulations. However, data obtained from take-off force measurements did not correlate with the quantified amount of sticking. Although pronounced sticking was observed, the measured tablet take-off forces remained low even at high drug contents. These results indicate that the tablet take-off force is not a direct indicator of the sticking tendency of ibuprofen tablet formulations. It is suggested that the evaluation of take-off force data requires a differentiated approach. A new interpretation of take-off force data is presented in this paper.