Can Exposure to Sunlight Lower Your Medication Levels?

Sunlight does more than just lift your spirits; it may alter medication levels when you're outside enjoying it. According to a new study published in the journal Drug Metabolism and Disposition, sunlight can alter the metabolism of medications - or the rate of medication breakdown. Something to think about if you're a sun worshiper.

Sunlight and Medication Levels

Researchers looked at medication levels of patients who had undergone organ transplants. These patients were taking drugs to suppress their immune system, so they required frequent monitoring of their medication levels. When they compared medication levels on these folks in the summer with those checked during the winter months, they found significant variations.

During the spring and summer months when sunshine abounds and people absorb more vitamin D, researchers found that medication levels for these immune-suppressing drugs were at their lowest - but when the season changed and vitamin D levels were lower due to lack of sunlight, medication levels rose.

Why would medication levels drop when it's sunny outside? It's not clear whether the metabolism of all medications is affected by sunlight, but researchers have a theory as to why this happens. People have higher vitamin D levels during the summer months, because vitamin D is formed when sunlight hits vitamin D precursors on the skin. Vitamin D activates an enzyme in the liver called CYP3A4 that plays a role in the metabolism of medications. This increases medication breakdown and lowers blood levels of the drug.

This surprising finding may at least partially explain why medication levels vary among individuals and why some people are better able to handle poisons and toxic exposures than others. It's possible that people who live in bright sunny climates and absorb a lot of vitamin D need to take more of certain medications, if this research holds true for all drugs.

Sunlight and Medications Don't Always Mix

Some medications even commonly used ones like antibiotics and cold medications increase sensitivity to the sun and can cause severe rashes, burned skin or hives. It's always a good idea to avoid going out in the sun for prolonged periods of time until you know whether the medication you're taking is a photosensitive one.

The Bottom Line?

Taking medications and going out in the sun could lead to a bad rash or burn, or it could lower medication levels in your bloodstream. Ask your doctor about sun precautions when you're taking medications - to be safe.

References:

Eurekalert.org. "Sunlight Can Influence the Breakdown of Medicines in the Body"

Merck Manual. Eighteenth edition. 2006.