CALCULATION OF 8-METHOXYPSORALEN DOSE ACCORDING TO BODY-SURFACE AREA IN PUVA TREATMENT

In 41 patients about to start PUVA, the dose of 8-methoxypsoralen (8-M OP) was calculated conventionally according to body weight (0 . 6 mg/k g), or according to body surface area (25 mg/m(2)) predicted from heig ht and weight measurements. The two different methods of dosing were u sed on consecutive treatment days and the plasma 8-MOP concentration w as measured on each occasion 2 h after ingestion of the crystalline fo rm of 8-MOP, given to the nearest 10 mg. Body weight calculated doses ranged from 30 to 60 mg with a significant difference in the plasma 8- MOP concentration between the dose groups, indicating a systematic var iation according to the weight of the patient. When calculated accordi ng to body surface area, only two doses were used (40 or 50 mg), and t here was no significant difference in plasma 8-MOP concentration betwe en the groups. Calculation of the dose of 8-MOP using body surface are a may be performed quickly and simply provided the height and weight o f individual patients is known. We provide evidence that this method o f dosing will improve the therapeutic effect of PUVA in psoriasis.