In vivo dissolution measurement with indium-111 summation peak ratios

Dissolution of [111In]labeled tablets was measured in vivo in a totally noninvasive manner by using a modification of the perturbed angular correlation technique known as the summation peak ratio method. This method, which requires the incorporation of only 10-12 microCi into the dosage form, provided reliable dissolution data after oral administration of [111In]lactose tablets. These results were supported by in vitro experiments which demonstrated that the dissolution rate as measured by the summation peak ratio method was in close agreement with the dissolution rate of salicylic acid in a [111In]salicylic acid tablet. The method has the advantages of using only one detector, thereby avoiding the need for complex coincidence counting systems, requiring less radioactivity, and being potentially applicable to a gamma camera imaging system.