Although a sunny day is certainly a great joy for many, sun exposure is not as harmless as it seems at first glance. In addition to the negative consequences that you can read more about at the link, the interaction of some medications and the sun’s rays can also be dangerous. The reaction can occur when exposed to the sun’s UVB rays, but most are caused by exposure to UVA rays that penetrate deeper into the skin. It is important to emphasize that UVA rays are almost the same throughout the year, while the intensity of UVB rays changes and they are strongest in the summer months and around noon.
The reaction caused by the interaction of the sun and some chemical components of drugs is called photosensitivity. Depending on the cause, it can be phototoxic or photoallergic, with phototoxic reactions being more common. It is caused by the activation of the medicine when exposed to the sun when the medicine is injected, applied orally or applied to the skin. The drug absorbs UV radiation, releases it into the skin and ultimately causes cell death. Within a few hours, symptoms appear on exposed parts of the body and stop after the drug is removed.
The photoallergic reaction occurs after applying the drug to the skin surface. Ultraviolet rays of the sun cause a structural change in the drug. The drug then becomes an immunogen and causes the production of antibodies, which causes a reaction to the sun after a few days. The reaction is characterized by eczema (rash) on exposed areas of the skin and can spread to parts of the body that have not been exposed to the sun. In this case, the reaction does not stop immediately after the drug is removed from the body.
Likelihood of photosensitivity and risk reduction
It is important to note that not every organism will respond equally to a photosensitive drug. The reaction does not even have to occur every time after taking the medicine with sun exposure. In addition to these phototoxic and photoallergic reactions, exacerbations of existing skin problems, including eczema and herpes, may occur. There have even been cases in which there has been a worsening or even induction of autoimmune disorders such as lupus.
If you are taking a medicine with potential photosensitivity properties and you need to go out in the sun, try to reduce the risk of developing a reaction by following these instructions:
- look for shade – especially between 10 and 16 hours
- keep in mind that the sun’s rays can be stronger when they bounce off water, sand, and snow
- wear lightweight and light-colored clothing, sunglasses, and a hat
- use sunscreen regularly and as directed – preferably with an SPF value of 30 or higher
Which medications should be monitored?
- Antibiotics (quinolones, sulfonamides, tetracyclines, trimethoprim, levofloxacin)
- Antifungal agents (flucytosine, griseofulvin, voriconazole)
- Antihistamines (cetirizine, diphenhydramine, loratadine, promethazine, cyproheptadine)
- Cholesterol-lowering drugs (simvastatin, atorvastatin, lovastatin, pravastatin)
- Diuretics (thiazide diuretics: hydrochlorothiazide, chlorthalidone, chlorothiazide; other diuretics: furosemide and triamterene)
- Nonsteroidal anti-inflammatory drugs (ibuprofen, naproxen, celecoxib, piroxicam, ketoprofen)
- Oral contraceptives and estrogens
- Medications for depression (amitriptyline)
- Phenothiazines (chlorpromazine, fluphenazine, thioridazine, prochlorperazine)
- Psoralens (methoxsalen, trioxane)
- Retinoids (acitretin, isotretinoin)
- Sulfonylureas for type 2 diabetes (glipizide, glyburide)
- Alpha-hydroxy acids (AHA) in cosmetics
These medicines are one of the most common photosensitivity medicines, but if you have any doubts about a medicine that is not listed, we advise you to consult your doctor or pharmacist for additional information.
Translated by Filip Sakoman
2. The Sun and Your Medicine, 2015, https://www.fda.gov, accessed 24.5.2020.
3. Sunce kao (ne)prijatelj našoj koži, 2019, https://recipe-cpsa.com, accessed 24.5.2020.
4. Lijekovi i sunce, 2010, https://www.plivazdravlje.hr, accessed 24.5.2020.