Comparative stability of repackaged metoprolol tartrate tablets

The stability of metoprolol tartrate tablets packaged in original high density polyethylene containers and repackaged in USP Class A unit-dose blister packs was investigated. Studies were conducted at 25 °C/60% relative humidity (RH) for 52 weeks and at 40 °C/75% RH for 13 weeks. The potency, dissolution, water content, loss on drying and hardness of the drug products were analyzed. Results indicated no differences in the stability between the tablets in both packages stored under 25 °C/60% RH. No difference in potency was found in both packages under either condition. However, a significant weight increase due to moisture uptake was observed for the repackaged tablets stored under 40 °C/75% RH. The weight increase was accompanied by a decrease in tablet hardness (6.5–0 kp) and a increase in dissolution rate (51–92%) in 5 min. Near-infrared (NIR) chemical imaging also monitored moisture uptake of the tablet non-invasively through the package. The observed changes in product stability may adversely affect the products bioavailability profile, even though the potency of the active drug remained within USP specification range of 90–110%. Study results suggest product quality can be negatively impacted even when using USP Class A repackaging materials.