Different issues with different phototherapies How long the drug is to be taken for and when during or before phototherapy it is started is key when deciding if any action needed There are many ways a drug can cause skin photosensitivity ID: 808518
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Slide1
Phototherapy and Photosensitising Drugs
Slide2Different issues with different phototherapies
How long the drug is to be taken for and when during, or before, phototherapy it is started is key when deciding if any action needed
There are many ways a drug can cause skin photosensitivity
Sunburn-like phototoxicity is most common
Phototoxicity is dose related (e.g., 200mg daily doxycycline frequently photosensitises to UVA in fair-skinned people but usually 100mg daily doxycycline does not do so)
Even when the mechanism is phototoxicity not
everone
will react even with a high dose – often drug metabolites are the main problem and our metabolising systems differ)
Slide3Slide4Narrowband ultraviolet B
Most photosensitising drugs are not an issue
as ultraviolet A (UVA) is much more likely to cause problems with most drugs.
There are some exceptions (see new
Photonet
guidance on drugs that might be a problem and commonly started drugs that are not a problem).
If drug precedes phototherapy then starting with minimal erythema dose assessment or other small area test
befor
whole-body treatment is all that is needed.
If a potentially problematic drug is for a short course often best to temporarily stop UVB.
If started during phototherapy course and a long course is planned an individual plan must be made (What drug? What drug dose? How far into UVB course and dose reached compared with baseline MED if checked?)
Slide5Photosensitizing drugs may lower the narrow‐band ultraviolet B (TL‐01) minimal erythema dose
Cameron H & Dawe RS. British Journal of Dermatology, Volume: 142, Issue: 2, Pages: 389-390, First published: 24 December 2001, DOI: (10.1046/j.1365-2133.2000.03325.x)
NSAIDs, phenothiazines and calcium channel blockers associated with lower pre-treatment narrowband UVB MEDs
Slide6Are photosensitizing medications associated with increased risk of important erythemal reactions during ultraviolet B phototherapy?
Harrop G et al. British Journal of Dermatology, Volume: 179, Issue: 5, Pages: 1184-1185, First published: 19 May 2018, DOI: (10.1111/bjd.16800)
Potentially phototoxic drugs
associated with
(might not
cause
) more important erythema episodes during UVB courses.
Slide7PUVA
Not normally an issue
as psoralens are usually so much more photosensitising so addition of another phototoxic drug is rarely relevant.
For example, an individual’s minimal erythema dose with UVA might be 30 J/cm² but their minimal phototoxic dose with PUVA might be 0.5 J/cm² (so a phototoxic index of 60) whereas another highly UVA photosensitising drug such as ciprofloxacin might still only have a phototoxic index of 3.
If MPDs are not done
, caution is needed with any new UVA sensitising drugs in case the patient is effectively just getting UVA (not “proper” PUVA).
In general, it is best to be cautious with short (e.g. antibiotic) courses and temporarily with-hold PUVA.
Slide8UVA (either broadband UVA [PUVA cubicle without psoralens] or UVA1)
Drug induced phototoxicity more of a concern, but these treatments not widely used – best to seek individual advice from referring
clinicisn
if unsure.
Slide9Summary
See guidance on or soon to be on
Photonet
website.
In most situations the main risk of potentially photosensitising drugs is that effective phototherapy might be compromised by excessive caution.