Simultaneous determination of hydroxocobalamin and its cyanide complex cyanocobalamin in human plasma by high-performance liquid chromatography. Application to pharmacokinetic studies after high-dose hydroxocobalamin as an antidote for severe cyanide poisoning.

Hydroxocobalamin (OHCbl) is a powerful antidote for cyanide poisoning, via the formation of non-toxic cyanocobalamin (CNCbl). Plasmatic cobalamins were measured at 361 nm, after enrichment and purification on a short C18 precolumn (1% acetic acid; 1 ml min-1; 2 min), by back-flush elution on a C18 ODS-2 column [0.1 M sodium dihydrogenphosphate-methanol (63:27, v/v) (pH 4.0); 0.80 ml min-1]. The precision was 3.21 and 3.54% for 10 microM OHCbl and CNCbl, respectively. The method was used to study the pharmacokinetics of OHCbl and the formed CNCbl in severely poisoned patients.