Determination of Trimethylpsoralen in Blood, Ophthalmic Fluids, and Skin

Trimethylpsoralen (TMP) levels in the blood of vitiligo patients were determined through the use of a high-performance liquid chromatographic method. TMP was extracted from blood buffered at pH 9.0 with 95:5 (V/V) hexane-isopropanol mixture; evaporated to dryness, and reconstituted in 50 μl of ethanol, A 10-μl aliquot was injected into a Micropack MCH-10 column (Varian HPLC model #5000). The mobile phase consisted of a mixture of water and acetonitrile with a linear gradient. The retention time of TMP was 16.5mm, The calibration curve of the external standards was linear. Overall recovery of the internal stands was 75–92%, with the lower detection limit of TMP at 2ng/ml. Peak blood levels as low as 140ng/ml and as high as 800ng/mI were obtained in vitiligo patients 1–2hr following the oral administration of 30mg of trioxsalen tablets (Paul B. Elder Co.). Blood TMP levels peaked consistently at 2hr when patients were fasted for 8hr prior to drug ingestion. These results are consistent with the clinical observation that maximum response due to phototherapy is obtained 1–2hr after oral administration of the drug. Two hours after oral drug administration, TMP levels in the epidermis, dermis, and whole skin of the guinea pig (in ng per g tissue) were; epidermis, 226 ± 15; dermis, 25 ± 6; and whole skin 176 ± 12. Also detected were TMP levels 244 ± 17ng/ml in aqueous humor and 63 ± 6mg/mi in vitreous humor. These results point to the fact that the eyes of patients must be protected from overexposure to sunlight after psoralen-ultraviolet treatment