Bioavailability of vitamin D3 in non-oily capsules: the role of formulated compounds and implications for intermittent replacement.

OBJECTIVE To evaluate the bioavailability of vitamin D in capsules as compared with oily drops in nuns living in a closed community with very low sun exposure. METHODS A randomized, 2 x 2 crossover, open clinical trial was conducted, with 18 nuns aged between 20 and 75 years. Samples were collected in the fasting state and at 4, 8, 12 and 24 hours following the administration of capsules and oily drops (both containing vitamin D3 66,000 UI plus vitamin A 13,200 UI) to determine serum 25 hydroxyvitamin D concentrations (25OHD), at baseline and 90 days after. The evaluation was based on the maximum concentration (Cmax) and area under the curve (AUC0-24). RESULTS The capsule formulation presented Cmax and AUC0-24, 5.78% and 0.76%, respectively, greater than the oily drops formulation. CONCLUSION Both formulations were within the limits for a bioequivalence study, namely C-90% for Cmax and AUC0-24, and the drugs were considered bioequivalent.