Psoralen UV-A therapy (PUVA) is used for the treatment of psoriasis1 and cutaneous T-cell lymphoma.2 The efficacy may be related to the amount of drug present at the time of irradiation. From 1988 to 1996, 5274 blood specimens were collected from patients receiving photochemotherapy and analyzed by high-pressure liquid chromotograpy.3 Patients for whom at least 10 determinations were made (1029 determinations in 68 patients) were selected for detailed analysis. We show that it is not uncommon for patients to have very low levels of methoxsalen.
Donath P, Bethea D, Amici L, DeLeo K, Wang X, Battista J, Knobler RM, Gasparro FP. Low and Irreproducible Methoxsalen Levels in Patients Receiving Photochemotherapy. Arch Dermatol. 1999;135(5):604-606. doi:10-1001/pubs.Arch Dermatol.-ISSN-0003-987x-135-5-dlt0599