A rapid HPLC procedure for the simultaneous determination of chloroquine, monodesethylchloroquine, diazepam, and nordiazepam in blood.

Chloroquine, monodesethylchloroquine, diazepam, and nordiazepam levels are simultaneously determined in whole blood or plasma by HPLC. Papaverine is used as internal standard, and the analysis is performed after protein-binding hydrolysis, absorption on Extrelut, and elution with diethyl ether/methylene chloride (70:30 v/v). UV detection is used at 343 nm for 12 min, then changed to 242 nm. There are two mobile phases with two flow rates. The procedure requires 30 min, is reproducible, sensitive (8-10 ng/mL for chloroquine and its metabolite, 4 ng/mL for diazepam and nordiazepam), and selective, especially towards other antimalarial agents and drugs like adrenaline or barbiturates, which may be used in chloroquine poisoning therapy. It can be used for pharmacokinetic studies, therapeutic control, to establish the diagnosis and prognosis of a chloroquine poisoning, and to follow and optimize treatment.