Pharmacokinetic and In-Vitro Characteristics of Sustained Release Verapamil Products

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Abstract
The in-vitro dissolution and in-vivo pharmacokinetics of two marketed sustained release formulations, Verelan (V) and Isoptin SR (ISR), were compared. The effect of food on V was also examined in a separate study with conventional Isoptin (I) as a reference. Both sustained release preparations had extended dissolution profiles with 50% release times (T50%) of 4 hours for ISR and 8 hours for V. The extended in-vitro profile of V versus ISR was confirmed in-vivo with a Tmax of 7.3 hours compared to 5.0 hours, a Cmax of 114.3 compared to 171.0 and a peak to trough ratio of 3.8 compared to 10.1 for V and ISR respectively. In a second pharmacokinetic study the rate and extent of absorption of verapamil from V was shown to be unaffected by food.