Methoxsalen, also called 8-MOP, is a synthetic version of a natural compound called psoralen. Doctors use it with UVA light to treat skin problems like psoriasis, vitiligo, and eczema. The drug makes the skin more sensitive to UV light, so a short UVA session can calm the rash or help repigment white patches.
When you take methoxsalen by mouth, it spreads through your bloodstream and reaches the top layers of skin. Then the UVA lamp activates it, creating tiny chemical bonds that slow down the over‑active skin cells. This process reduces scaling, redness, and itching.
Most patients hear about methoxsalen in the context of PUVA therapy – that’s Psoralen + UVA. In psoriasis, the combination can clear stubborn plaques that haven’t responded to creams. Vitiligo patients often see new pigment appear after a few weeks of regular PUVA sessions.
Dermatologists also prescribe methoxsalen for severe atopic dermatitis and some types of cutaneous T‑cell lymphoma. Outside of skin, the drug is sometimes used in research to study how DNA reacts to UV light, but that’s not a typical patient use.
Doctors usually start you on a low dose, like 0.5 mg per kilogram of body weight, taken about two hours before UVA exposure. The exact amount can change based on how your skin reacts. Some people need a higher dose after a few treatment cycles, while others stay on the low end to avoid side effects.
It’s important to follow the timing exactly. If you take the pill too early or too late, the UVA light won’t work as well, and you could waste a session. Most clinics give you a printed schedule, and many have apps that remind you when to take the medication.
Never skip the UVA part. Taking methoxsalen without the light can increase your risk of skin irritation and doesn’t give you any benefit.
The biggest thing to watch for is sunburn‑like skin irritation. If you notice redness, itching, or a rash after a PUVA session, tell your doctor right away. They might lower the dose or space out the treatments.
Other possible side effects include nausea, headache, and mild fatigue. A small number of people develop eye problems, so doctors often recommend wearing UV‑blocking glasses during treatment.
Because methoxsalen makes skin more sensitive to UV, you’ll need to avoid direct sunlight for at least 24 hours after each session. Use sunscreen with SPF 30 or higher, wear protective clothing, and stay in the shade when you’re outdoors.
Long‑term use has been linked to a slightly higher risk of skin cancer, so regular skin checks are a must. Your dermatologist will monitor any new moles or changes during follow‑up visits.
Pregnant or breastfeeding women should not use methoxsalen unless a doctor says it’s absolutely necessary. The drug can cross the placenta and might affect a newborn’s skin.
In short, methoxsalen can be a powerful tool for stubborn skin issues, but it works best when you stick to the dosage schedule, protect yourself from extra UV, and keep an eye on any side effects. Talk with your dermatologist to see if PUVA therapy fits your needs, and make sure you understand the safety steps before you start.