Published: 8 December 2016
Prescriber Update 37(4): 60-61
As the summer approaches, be aware that there may be a risk of drug-induced photosensitivity.
Drug-induced photosensitivity is an adverse skin reaction induced by sun exposure in some patients taking particular medicines1. As the skin absorbs ultraviolet (UV) radiation this can cause a chemical change to a medicine that is present in the skin resulting in a phototoxic or photoallergic reaction2.
Phototoxic reactions are more common than photoallergic reactions3. These reactions are due to cellular damage from the altered medicine in sun-exposed areas and are dose-dependent. Phototoxic reactions can appear within minutes to hours after exposure4. Clinical presentation varies from mild burning and stinging to exaggerated sunburns with erythema and oedema of the sun exposed areas. Hyperpigmentation may also occur1,4.
Photoallergic reactions have an immunological basis3,4. The UV radiation transforms the medicine into an antigen that triggers an allergic response. These reactions are typically delayed, developing after 24 to 72 hours. The presentation is generally of eczematous dermatitis which can spread across the whole body beyond the exposed areas2,4.
The top 10 medicines suspected to have caused photosensitivity reactions reported (between April 1965 and September 2016) to the Centre for Adverse Reactions Monitoring (CARM) are:
See Dermnet* (www.dermnetnz.org/topics/drug-induced-photosensitivity/) for a list of medicines that can cause photosensitivity.
For patients who have experienced a photosensitivity reaction, medicine discontinuation and sunlight avoidance remain the mainstay of treatment. Depending on the severity of the reaction, topical or systemic corticosteroids can be used for symptom alleviation.
Not everyone will experience photosensitivity reactions but sensible precautions for patients taking medicines that can cause photosensitivity include1,2:
Further information is available at the New Zealand Dermatological Societyˆ (www.dermnetnz.org/topics/drug-induced-photosensitivity/).
Please continue to report any adverse reactions to CARM. Reports can be submitted on paper or electronically (https://nzphvc.otago.ac.nz/).
* Dermnet New Zealand
ˆ New Zealand Dermatological Society is now Dermnet New Zealand