Photosensitizing drugs
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Photosensitizing drugs are pharmacological substances that increase the skin's sensitivity to ultraviolet (UV) radiation or visible light. This phenomenon is referred to as photosensitization (photosensitizing skin reaction) and can lead to inflammatory changes resembling sunburn, hyperpigmentation, rashes, or allergic reactions after light exposure. This mechanism results from the interaction between a drug molecule present in the skin and the energy of the light radiation, which initiates chemical reactions that damage skin cells. Photosensitization can occur after both oral and topical use of drugs. This phenomenon has important clinical significance because it increases the risk of skin complications during sun exposure and during procedures that use light or laser energy.
Photosensitizing drugs – what does it mean?
The term photosensitizing drugs refers to substances that, after being absorbed by the body or applied to the skin, can cause an excessive skin reaction to light. In clinical practice, two basic types of photoreactivity are distinguished:
1. Phototoxic reactions
They are the most common and occur in many people at an appropriate drug dose and light exposure. Their mechanism involves:
- the drug molecule absorbing the energy of UV radiation,
- the formation of reactive oxygen species (ROS),
- damage to membrane lipids, proteins and DNA.
Symptoms usually appear a few hours after light exposure and resemble a severe sunburn. They may include:
- skin redness,
- burning and pain,
- swelling,
- blisters,
- later post-inflammatory hyperpigmentation.
2. Photoallergic reactions
These are much rarer and are immune-mediated. In this case:
- light changes the structure of the drug molecule,
- a new antigen is formed,
- the immune system triggers a delayed-type allergic reaction.
Symptoms usually appear after 24–72 hours and are eczematous in nature (rash, itching, papules).
Photosensitivity can persist from several days to even several weeks after the end of therapy, depending on the drug's metabolism and its accumulation in the skin.
Photosensitizing drugs – what are they?
Many groups of pharmaceuticals exhibit photosensitizing potential. The risk depends on the drug dose, duration of use, and the individual sensitivity of the patient. The most commonly mentioned include:
Antibiotics
Some antibiotics strongly increase the skin's sensitivity to light:
- tetracyclines (e.g., doxycycline, tetracycline),
- fluoroquinolones (e.g., ciprofloxacin),
- sulfonamides.
Dermatological drugs
- retinoids (e.g., isotretinoin, acitretin),
- some anti-acne preparations,
- agents used in the treatment of psoriasis.
Retinoids additionally cause thinning of the stratum corneum, which increases the skin's susceptibility to light-induced damage.
Cardiovascular drugs
Some preparations used in cardiovascular diseases also exhibit photosensitizing effects:
- amiodarone,
- some thiazide diuretics (e.g., hydrochlorothiazide),
- selected antihypertensive drugs.
Anti-inflammatory and analgesic drugs
- ketoprofen (particularly in topical formulations),
- naproxen,
- other nonsteroidal anti-inflammatory drugs (NSAIDs).
Psychiatric drugs
Some psychotropic drugs may also cause photosensitivity:
- phenothiazines,
- selected antidepressants.
Herbal preparations
Photosensitization can also be caused by plant constituents, especially:
- St. John's wort (Hypericum perforatum),
- preparations containing furanocoumarins.
In clinical practice this means that a patient taking such substances should limit exposure to UV radiation and use high photoprotection.
Photosensitizing drugs and laser
The phenomenon of photosensitization is significant in the context of dermatological and aesthetic medicine procedures using light or laser energy. The presence of photosensitizing drugs in the body can increase the risk of complications such as:
- severe erythema,
- skin burns,
- blisters,
- post-inflammatory hyperpigmentation,
- scarring.
Therefore, before performing light or laser procedures a thorough medical history regarding medications taken is necessary.
Particular caution is exercised for procedures such as:
- laser removal of vascular lesions,
- laser treatment of hyperpigmentation,
- laser skin rejuvenation,
- laser scar removal,
- laser therapy for acne lesions,
- procedures using the Nd:YAG laser or other dermatological lasers.
In many cases it is recommended to stop the photosensitizing drug for a specified time before the procedure, if this is possible and safe with respect to the primary therapy. The washout period depends on the pharmacokinetics of the specific drug and may be:
- a few days (e.g., some antibiotics),
- a few weeks,
- in the case of retinoids – even several months.
For this reason, qualification for laser procedures should always be conducted by a physician or an experienced aesthetic medicine specialist, who will assess the potential risk of complications and select a safe time to perform the procedure.
