The tetracyclines differ in their skin side effects. Doxycycline is the most phototoxic of the commonly used tetracyclines: patients get an exaggerated sunburn, sometimes with photo-onycholysis, on exposed skin. Minocycline rarely causes phototoxicity but can cause blue-grey pigmentation in scars, on the shins or in the mouth with long-term use, and occasionally a drug-induced lupus or hepatitis. In Indian summers, a patient on doxycycline for acne or rosacea who works outdoors needs to be told.
- Warn patients starting doxycycline about sunburn on exposed skin and advise sunscreen and cover.
- Take doxycycline with a full glass of water and not lying down, to prevent oesophageal ulceration.
- Look for blue-grey pigmentation of scars, shins or gums at review in long-term minocycline users.
- Stop minocycline and check antinuclear antibodies and liver tests if joint pain, fever or rash develops.
Why it matters
Choosing between the two tetracyclines often comes down to the patient's sun exposure and how long they will take it.
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