Systemic drug photosensitivity-Culprits, impact and investigation in 122 patients.

Background: Systemic drugs are a potentially reversible cause of photosensitivity. We explore prevalence, impact, phototest findings and culprit drugs.

Methods: Retrospective review of patients was diagnosed with drug-induced photosensitivity in a specialist photoinvestigation centre (2000-2016), using data recorded in standardized pro forma. Patients underwent detailed clinical evaluation. Monochromator phototesting was performed to 300 ± 5 nm, 320 ± 10 nm, 330 ± 10 nm, 350 ± 20 nm, 370 ± 20 nm, 400 ± 20 nm, 500 ± 20nm and 600 ± 20 nm. Broadband UVA and solar-simulated radiation (SSR) testing were performed, and photopatch testing and laboratory tests examined for other causes of photosensitivity. DLQI was evaluated.

Results: Prevalence of drug-induced photosensitivity was 5.4% (122/2243) patients presenting with photosensitivity. Patients with drug-induced photosensitivity were 52.5% female; median 62 years (range 11-86); phototype I (17.2%), II (39.3%), III (26.2%), IV (6.5%), V (4.1%). Fifty-five (45.1%) patients had reduced erythemal thresholds on monochromator phototesting: 83.6%% to UVA alone, 14.5% to both UVA and UVB, 1.8% to UVA and visible light; 61.4% (n = 75) showed abnormal response to broadband UVR. Drugs implicated: quinine (11.5%), diuretics (10.7%; thiazide 9.8%), antifungals (9.8%), proton-pump-inhibitors (9.8%), angiotensin-converting enzyme inhibitors (7.4%), anti-inflammatory drugs (6.6%), statins (5.7%), selective serotonin reuptake inhibitors (4.9%), calcium channel antagonists (3.3%), anti-epileptics (3.3%), tricyclic antidepressants (3.3%), beta-blockers (2.5%), antibiotics (2.5%), others (≤1.6% cases each). Emerging culprits included azathioprine (2.5%) and biologics (TNF-α inhibitors, denosumab; 2.5%). Median DLQI was 11 (range 2-27) for the past year.

Conclusion: Classically described photosensitizing drugs such as thiazides and quinine remain common offenders, while emerging culprits include biologics such as TNF-a inhibitors and proton-pump-inhibitors. There is very large impact on life quality; identification facilitates measures including drug cessation and implementation of appropriate photoprotection.