In vitro and in vivo evaluation in healthy human volunteers of floating riboflavin minitablets

This work relates to sustained-release floating minitablets which are able to float on the surface of aqueous fluids for an extended period of time. Firstly, granules were prepared by melt granulation and then, compressed into minitablets to obtain a multiple-unit system. Formulations were based on the use of a meltable binder, a swellable hydrocolloid and on a mixture of gas-generating agents. In vitro and in vivo evaluations of floating capability were performed. To assess the usefulness of the intragastric buoyancy properties of the floating minitablets (FMT), non-floating minitablets (NFMT) with in vitro riboflavin (RF) release profiles equivalent to the FMT were prepared. FMT and NFMT were administered orally to nine healthy volunteers. The volunteers were divided into two groups, a fasted group (n = 5) and a fed group (n = 4). The pharmacokinetic parameters were investigated by analysis of riboflavin urinary excretion leading to the observation that the mean amount of riboflavin excreted in the urine seemed to increase when FMT were administered after a meal, but did not increase when NFMT were administered. As riboflavin has a narrow absorption window in the upper part of small intestine, this phenomenon could be attributed to gastric retention of the floating minitablets.