In vitro disintegration studies of weekly generic and branded risedronate sodium formulations available in Canada

The aim of this study was to evaluate the in vitro disintegration of the five newly available Canadian generic risedronate 35 mg tablets compared to the innovator (branded) product, ACTONEL * *ACTONEL is a registered trade name of Warner Chilcott Company, LLC. (risedronate sodium) 35 mg.

Tablets were inspected for colour and appearance. Disintegration times were determined using United States Pharmacopeia 33 (USP33-NF 28) methods. Disintegration onset time was also evaluated.

The mean disintegration onset time values for the generic risedronate 35 mg tablets ranged from 2 to 29 seconds, and the mean disintegration completion times ranged from 81 to 260 seconds. The mean disintegration onset and completion time values for the ACTONEL 35 mg tablets were 23 and 43 seconds respectively. Four out of the five generic tablets tested had shorter disintegration onset times than the branded product; two of the generic tablet products had very fast disintegration onset times i.e. 2-3 seconds. Disintegration completion time for all five generic products tested was longer than that observed for the branded product; two generic products had disintegration completion time values five to six times longer than the branded product.

Differences in the in vitro disintegration times were observed between the generic risedronate 35 mg tablets commercially available in Canada and the branded product, ACTONEL. The rapid disintegration onset times of two generic products may be important as this could increase the possibility of drug exposure in both the mouth and the esophagus during swallowing, resulting in unwanted localized irritation. However, it should be noted that an in vitro/in vivo correlation has not been established. Until such studies are completed it may be important to be aware of such in vitro disintegration differences when evaluating patients with newly presenting upper gastrointestinal complaints upon being switched from the branded product to generic formulations.