Quantification of uracil, dihydrouracil, thymine and dihydrothymine for reliable dihydropyrimidine dehydrogenase (DPD) phenotyping critically depend on blood and plasma storage conditions.

Establishing dihydropyrimidine dehydrogenase (DPD) activity is highly important in determining the correct starting dose of fluoropyrimidines such as 5-fluorouracil and capecitabine. The concentration ratio of endogenous uracil with its metabolite dihydrouracil (DHU) is a well-known parameter that is linked to DPD activity. Concentration ratios such as thymine over its DPD-converted metabolite dihydrothymine (DHT) is less described and may serve as an alternative diagnostic biomarker for DPD activity.

[Convulsions due to an interaction between anti-epileptic drugs and rifampicin].

Background: Anti-epileptic drugs (AEDs) have a small therapeutic window, so it is important to monitor plasma levels. Inadequate plasma levels may lead to convulsions. Many AEDs are cleared hepatically, and there are many drug interactions that are known to lead to changes in plasma levels.

The local production of 1,25(OH)2D3 promotes osteoblast and osteocyte maturation.

Maintenance of an adequate vitamin D status, as indicated by the level of circulating 25-hydroxyvitamin D (25(OH)D), is associated with higher bone mass and decreased risk of fracture. However, the molecular actions of vitamin D hormone (1,25(OH)2D3) in bone are complex, and include stimulation of osteoclastogenesis via RANK-ligand up-regulation, as well as the inhibition of mineralisation. We hypothesise that these divergent data may be reconciled by autocrine actions of 1,25(OH)2D3 which effect skeletal maintenance, as opposed to endocrine 1,25(OH)2D3 which acts to maintain serum calcium homeostasis.