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Sunlight, Vitamin D Levels May Affect Drug Response


Could the amount of sunlight you expose yourself to have an effect on your body’s response to drugs? A new study from Karolinska Institutet has indicated that the body’s ability to metabolize medications may be related to how much sunlight exposure people get.

Your drug response may change with the seasons

The role of vitamin D in health has been the topic of much discussion and research in recent times, with the vitamin being credited with helping to reduce the risk of Parkinson’s disease and of certain cancers, serving as a possible treatment for depression, and promoting bone health.

A study for publication in the journal Drug Metabolism & Disposition reports that concentrations of tacrolimus and sirolimus, drugs taken by organ transplant recipients to suppress the immune system and prevent organ rejection, vary during the year in a way that reflects fluctuations of vitamin D levels in the body.

The study also included the immune-suppression drug cyclosporine; however, this drug did not demonstrate the same activity as did tacrolimus and sirolimus.

To arrive at their finding, investigators reviewed nearly 70,000 analyses from patients who had had their blood levels of immune suppressive drugs monitored regularly. When samples obtained during the winter (January-March) were compared with those collected in late summer (July-September), the researchers observed a difference in drug concentrations.

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Specifically, drug levels in the patients were lowest when their vitamin D levels were at their highest. This discovery provides researchers with a new model to explain why the effects of drugs differ among patients and how a person’s environment may impact his or her ability to cope with toxins.

Vitamin D is a nutrient that differs from other vitamins in that the body produces much of its supply from exposure to sunlight. The effect of vitamin D on drug concentrations is believed to be related to its activation of the liver to increase production of an enzyme called CYP3A4, which is involved in the breakdown of tacrolimus and sirolimus. This enzyme also has a role in the metabolism of other medications as well.

One of the study’s authors, Jonatan Lindh at the Department of Laboratory Medicine, explained that if the body’s ability to breakdown a drug increases, “then higher doses of a drug are normally required in order to achieve the same effect.”

Although more research is necessary to confirm the results seen in this study, Lindh noted that “CYP3A4 is considered to be the most important enzyme in drug turnover in the body, and the results may have significance for many drugs.” Drugs metabolized by CYP3A4 are called CYP3A4 substrates, and there are scores of drugs in this category.

The results of this study are the first to be published regarding the impact of vitamin D, and possibly sunlight, on CYP3A4 activity in drug treatment of patients. This finding could have significant implications for many patients who receive medications affected by this enzyme.

Lindh JD et al. Drug Metabolism & Disposition 2011 Feb 24; doi: 10.1124/dmd.111.038125