A pharmaco-scintigraphy study of riboflavin 5'-phosphate sodium capsules (1 vs. 4)

Abstract The comparative in-vivo disintegration, gastric emptying and bioavailability of 41 mg radiolabeled riboflavin 5′-phosphate sodium capsules administered as a single hard gelatin capsule or as four capsules was evaluated in human subjects. A total of 41 mg of riboflavin 5′-phosphate sodium and 7 MBq of technetium sulfur colloid were incorporated in a single gelatin capsule or the same dose was administered in four capsules. A randomized crossover design was conducted in eight subjects under fasting conditions. Capsule disintegration and gastric emptying was measured by γ scintigraphy and the relative amount of riboflavin excreted in the urine was measured by HPLC. The in-vivo disintegration time and gastric emptying of the four capsules was significantly faster than for the one capsule. The bioavailability of the four capsule regimen was 16.5 versus 11.2% for the one capsule. The amount of riboflavin excreted in the urine in the 0–2 h interval was significantly greater for the four versus one capsule. The in-vivo performance of one 41 mg riboflavin 5′-phosphate sodium capsule is significantly different than the equivalent dose administered in four capsules. Further studies are needed to understand the underlying mechanism for the difference between the regimens.