Some medicines may cause (severe) skin reactions if the skin is exposed to UV light (from the sun or from an artificial source). The FAMHP is drawing attention to the different types of light sensitivity, which common medicines present an increased risk, the reports it has received, and a number of precautionary measures.
Sensitivity to light or photosensitivity
Some medicines increase the skin's sensitivity to UV light (from the sun or from an artificial source such as sunbeds or strong halogen lamps). These medicines are known as photosensitising medicines and may give rise to photodermatoses, skin conditions that are caused or exacerbated by UV exposure.
Photosensitisation may occur via two mechanisms, namely phototoxic and photoallergic reactions. Sometimes, the same medicine may cause both phototoxic and photoallergic reactions.
Phototoxic or non-allergic reaction
- This type is more common than photoallergic reactions and looks like severe sunburn, which may be accompanied by blistering.
- This reaction occurs rapidly after exposure and is usually limited to the exposed skin.
- It concerns a more severe reaction of the skin as a result of the interaction between the photosensitiser and light, which causes direct damage.
- The reaction depends on the dose. The medicinal product may be used again if the skin is effectively protected against the sun or UV rays.
- If the medicinal product is no longer used the skin damage will not occur again when the skin is exposed again to sunlight or UV rays.
Photoallergic reaction
- This is less common and occurs with some delay, after repeated or long-term use of the medicinal products. Consequently, it is often more difficult to make the connection with the product.
- This reaction may occur several days (to weeks) after exposure and may spread to non-exposed areas of skin.
- It involves an immune response that does not manifest itself until the skin is exposed to sunlight.
- Different kinds of skin reactions are possible, including eczema-like skin rash or skin rash with blisters.
- In rare cases, sunlight alone may cause the reaction to recur without any use of the medicine.
Which medicines are concerned?
The list of medicines that are incompatible with sunlight is long. A few examples of common medicines are given below. Hypersensitivity to UV rays is possible both after systemic administration and local application.
- Antibiotics (such as tetracyclines – doxycycline more than minocycline and quinolones).
- Antidiabetics (such as hypoglycaemic sulfonamides).
- Antimycotics (such as itraconazole, voriconazole and recently posaconazole).
- Psychopharmaceuticals (such as phenothiazine, carbamazepine, fluoxetine and St John's wort).
- NSAIDs (non-steroidal anti-inflammatory drugs, systemic (probably mainly piroxicam) and local (probably mainly ketoprofen gel)).
- Immunomodulating medication (such as tacrolimus and pimecrolimus).
- Cardiovascular drugs (such as amiodarone, fibrates, thiazide diuretics and loop diuretics).
- Medicines for osteo-articular conditions (such as methotrexate).
- Medicines to treat acne (such as retinoids).
The package leaflet and the summary of product characteristics (SmPC) for the medicine always state clearly if the medicine may cause such reactions.
Precautionary measures
- Avoid direct sunlight between the hours of 12.00 pm and 4.00 pm, when the sun's rays are strongest. Remember that the sun's rays are also stronger when reflected off water, snow and sand.
- Use a sun cream with a high sun protection factor. This is not always enough to prevent photosensitivity, however.
- Wear protective clothing with long sleeves (such as a long-sleeved T-shirt and long trousers), sunglasses and a wide-brimmed hat, if necessary.
- Consider alternative medicines if possible.
- Use of different photosensitising medicines should be avoided as this increases the risk of photodermatosis.
- It is recommended that doctors and pharmacists warn patients of the risk of exposure to sunlight and intensive artificial light, such as sunbeds, strong halogen lamps, and bright lights in operating theatres and in dental practices.
- If signs of photodermatosis appear, it is recommended that the patient stops using the suspected medicine immediately in consultation with the prescribing doctor.
Reports to the FAMHP
The following medicines have been reported more than once during the last ten years as being involved in a photoallergic or phototoxic reaction: NSAIDs (ketoprofen; n = 18), COVID-19 vaccines (n = 24), tetracyclines (doxycycline; n = 5), antitumoral medication (brigatinib, alectinib; n = 5), cardiovascular medicines (perindopril, amiodarone; n = 4), immunomodulators (dupilumab, vedolizumab; n = 4), medicines for pulmonary fibrosis (pirfenidone; n = 3), antihistamines (desloratadine; n = 2) quinolones (levofloxacin; n = 2).
With the exception of COVID-19 vaccines and for vedolizumab and dupilumab, the photosensitising properties of these medicines are well known.
The above reports relate to suspected side effects. This means medical events that were observed after use of medicines, but that were not necessarily related to or caused by the medication.
Reporting side effects
Patients and healthcare professionals are encouraged to report suspected side effects via eenbijwerkingmelden.be.