Sun exposure and drugs

In all of the aforementioned scenarios, ultraviolet radiation is responsible for the sun’s negative influences on drug therapy.Ultraviolet rays include:

• UVA – “long-wave”; affect the second layer of skin. UVA exposure is the main cause of sun-related drug side effects.
• UVB – “short-wave”; affect the top layer of skin. On rare occasions, these rays can also induce photosensitivity reactions.
• UVC – don’t reach the earth’s surface, but are found in artificial sources of UV radiation such as tanning beds.

Drug-induced photosensitivity might be caused by various mechanisms.

The absorption of UV radiation by phototoxic drugs (e.g. furosemide, amiodarone, tetracycline, ibuprofen etc.) can result in energy transfer to oxygen atoms and the subsequent creation of oxygen radicals. These radicals may change skin molecules, causing long-term damage or cell death. This mechanism is called phototoxicity and is manifested in the form of blisters, desquamation or hyperpigmentation. In some cases, due to DNA damage, phototoxic drugs may also induce the development of skin carcinoma.

Furthermore, UV rays can cause structural changes in drugs such as thiazides, quinidine, sulphonamides or topical ketoprofen, causing stimulation of our immune system which leads to photo allergic skin reaction. Photo allergy usually manifests as dermatitis.

It has to be noted that not only topical but also systemic intake of sun-sensitizing drugs can lead to photosensitivity reactions. In conclusion, when taking therapy which includes these drugs, it is important to apply sunscreen regularly and avoid sun exposure.