In vitro dissolution profile of two commercially available iron preparations.

BACKGROUND: Current scientific evidence indicates that anemia in pregnancy, regardless of severity, is associated with an increased risk of maternal and fetal mortality. There is little published information about the bioavailability and bioequivalence of formulations containing both iron and folic acid. However, in vitro dissolution studies can provide important information on the likely relative bioavailability of various formulations.

AIM: The objective of our study was to compare the in vitro dissolution of two similar commercially available formulations of iron- and folic acid-containing supplements, Folifer® (Bialport - Produtos Farmacêuticos, S.A., Portugal) and Ferroliver® (SM Pharma c.a., Venezuela), in order to determine the in vitro availability of their iron content. Folifer® and Ferroliver® were chosen because they contained similar amounts of elemental iron.

METHODS: The amount of iron released from each tablet was evaluated over a 4-hour period in three dissolution media replicating gastric or intestinal juices with pH values ranging from 1.5 to 6.9. The samples were then titrated with a solution of cerium ammonium sulfate in order to calculate the amount of iron released in each specific pH condition. The percentage of dissolved iron was calculated as a cumulative frequency, using the percentage of dissolved iron at all timepoints. The dissolution similarity between the two commercially available formulations was evaluated using the &U0192;(2) statistic formula.

RESULTS: During a 4-hour dissolution test, Folifer® released 59.4 mg of iron compared with 48.5 mg released by Ferroliver®. The value obtained for the similarity factor, an indicator of likely bioequivalence, was 41.

CONCLUSION: These data suggest that Folifer® releases more iron than Ferroliver®, and that the two formulations are not equivalent in vitro. The superior dissolution of ferrous sulfate with Folifer® compared with ferrous fumarate in Ferroliver® might be responsible for the observed difference.