HPLC determination of dextromethorphan and its metabolites in urine

An HPLC method for determination of dextromethorpan (DM), dextrorphan (DEX) , methoxymorphinan (MM) and hy droxymorphinan (HM) in urine with fluorescen ce detection (excitation and emission wavelength 280 and 310 nm) was elabor ated. The mobile phase was acetonitrile - 0.01 M-KH2PO4 3:2, triethylamine 350 mu l l(-1), pH 3.6; flow rate 0.7 ml.min(-1) internal standard betaxolo l (BX). For isolation of the substances from urine, liquid-liquid extractio n and re-extraction with freezing out the aqueous phase in all extraction s teps was used. The extraction yields were 97, 99, 83, 92 and 101 % for DM, DEX, HM, MM and EX, respectively. The method was used for determination of phenotype of cytochrome P 450 of isoenzyme 2D6 in a set of 102 healthy, unr elated volunteers from Czech population. In dependence on molar concentrati on ratios of DM and DEX in urine (metabolic ratio, MP), seven volunteers (6 .9 %) were classified as slow and 95 (93.1 %) as rapid metabolizers of DM ( MP < 0.3). The median in the former group was 1.3 (0.37-4.6) and 0.007 (0.0 001-0.18) in the latter.