Phototoxicity

Background

Certain drugs (and other chemicals) that penetrate the skin may cause reactions that occur only when the skin is exposed to light. This is a result of interactions between photons of light and the chemical within the skin.
Substances that cause such reactions are usually phototoxic in mechanism.

The skin manifestations of phototoxicity vary and include swelling, redness, blistering and pigmentation.

Phototoxicity is not immunologically based and can arise in anyone provided there is enough of the drug and appropriate radiation.

This issue has become increasingly important to patients, regulatory authorities and the pharmaceutical industry. Photosafety regulatory guidelines were introduced earlier this decade both in Europe and in the USA. Individual drug issues are assessed on a case by case basis with significant flexibility about which laboratory and clinical studies are considered necessary.