Drug-Induced Photosensitivity: Focus on Antibiotics

AUGUST 24, 2016
Photosensitivity reactions are well-known adverse effects of many drugs, including antimicrobials, nonsteroidal anti-inflammatory drugs, diuretics, and chemotherapeutic agents. In fact, an estimated 8% of adverse dermatologic reactions are linked to the photosensitizing effects of medications.1 
 
Since antibiotics that cause photosensitivity are commonly encountered in clinical practice, pharmacists should be aware of the potential for photosensitivity when dispensing and counseling patients taking these medications.

Phototoxicity vs. Photoallergy
Although these 2 subcategories of photosensitivity may be difficult to distinguish because of similar clinical manifestations, several notable differences exist.

Phototoxicity
Phototoxic reactions can occur in any patient who receives sufficient quantities of the drug and is exposed to enough light. Compared with photoallergic reactions, they require higher doses of the drug to occur and can appear at first drug exposure. Common phototoxic reactions are sunburns to the exposed areas of the skin, and later, hyperpigmentation to the same areas.2,3

Photoallergy
Photoallergic reactions are less common than phototoxic reactions and result from cell-mediated immunity. Like other allergic reactions, they don’t develop on first exposure and thus require sensitization. 
 
Unlike phototoxicity, a photoallergic reaction requires only a small amount of an offending agent and may be delayed for several days after exposure to light and the drug. Clinically, it resembles eczema and may spread to areas of the skin that weren’t exposed to light.2,3

Clinical Manifestations of Photosensitivity
The sites most frequently involved in photosensitivity reactions are those commonly exposed to light: the face, nuchal region, anterior portions of the leg, and the dorsa of the hands. The reactions typically look like an exaggerated sunburn with edema and erythema. In severe cases, however, blisters may form and patients will report burning, tenderness, and pain. Hyperpigmentation, a result of melanocyte proliferation or deposition of the drug and its photoproducts, may persist after the reaction’s acute phase has resolved. 

Other manifestations of photosensitivity are2:
·      Photo-onycholysis: The separation of the nail from the nailbed after exposure to ultraviolet (UV) radiation. Occurs most commonly with the use of tetracyclines.
·      Pseudoporphyria: Characterized by bullae, skin fragility, scarring, and easy bruising. Associated with tetracyclines and dapsone. Resolves after discontinuation of the offending drug.


Thomas Szymanski, PharmD
Thomas Szymanski, PharmD
Thomas Szymanski is PGY1 resident at Memorial Hermann-Texas Medical Center in Houston, TX. He earned his PharmD and a BA in French from the University of Rhode Island. His professional interests include cardiology and critical care. Thomas is an active member of ASHP and ACCP and has served on various national committees and advisory groups.
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