Determination of vitamin D3 conjugated metabolites: a complementary view on hydroxylated metabolites.

Experts typically define vitamin D deficiency levels by the determination of a circulating 25-hydroxyvitamin D3-calcifediol prohormone. A large part of the population is characterized by deficient vitamin D levels (calcifediol < 20 ng mL-1) despite individuals not being affected by any disorder. Cholecalciferol (vitamin D3) and/or calcifediol supplementation is a common practice for vitamin D-deficient individuals as recommended by international scientific societies and official agencies. In the last few years, several studies have reported the presence of conjugated vitamin D3 metabolites, mainly glucuronidation and sulfation derivatives, although simultaneous quantitative measurements involving phase I and II vitamin D metabolites have not been carried out. A quantitative method based on tandem mass spectrometry detection is proposed here for the combined determination of phase I and phase II vitamin D3 metabolites in human serum. As phase I and phase II metabolites are preferentially ionized in different modes, a switching polarity mode was adopted to determine both groups of compounds in serum at high sensitivity levels (pg mL-1). The validation of this proposal was successfully accomplished by following the Center for Drug Evaluation and Research (CDER) guidelines. Its applicability was tested in a cohort of volunteers with mostly deficient baseline levels. Considering the sulfated form of calcifediol, the sum of its concentrations showed sufficient baseline vitamin D levels in all individuals, suggesting that this could be a novel strategy for vitamin D deficiency definition. Therefore, phase II metabolites are proposed to be included when evaluating the vitamin D status since they provide more information about the overall status of the vitamin D endocrine system. Nevertheless, further studies are required to confirm the biological activity of these conjugated metabolites and the suitability of this strategy for the description of vitamin D deficiency.

The role of ultrasound in pharmaceutical production: sonocrystallization.

OBJECTIVES: The main aim of this review was to develop a critical discussion of the key role ultrasound (US) can play on the production of active pharmaceutical ingredients (APIs) by discussing the versatile effect this type of energy produces. METHODS: The different crystallization techniques that can be assisted and improved by US are discussed in the light of the available US devices and the effect pursued by application of US energy. Simple and complex analytical methods to monitor API changes are also discussed. KEY FINDINGS: The countless achievements of API US-assisted production are summarized in a table, and outstanding effects such as narrower particle size distribution; decreased particle size, induction time, metastable zone and supersaturation levels; or a solubility increase are critically discussed. CONCLUSIONS: The indisputable advantages of sonocrystallization over other ways of API production have been supported on multiple examples, and pending goals in this field (clarify the effect of US frequency on crystallization, know the mechanism of sonocrystallization, determine potential degradation owing to US energy, avoid calculation of the process yield by determining the concentration of the target drug remaining in the solution, etc.) should be achieved.