Mass fragmentographic determination of d- and l-chloropheniramine with aid of the stable isotope technique.

To investigate the pharmacokinetics of d-chlorpheniramine (d-CPA) and its l-isomer, d-CPA-d6 and l-CPA-d0 were administered orally and simultaneously to healthy adult volunteers. Both isomers in the serum were measured by chemical ionization-mass fragmentography using dl-CPA-d13 as an internal standard. The concentration of d-isomer was higher than that of l-isomer and the ratio (d/l) of both isomers was 1.9-3.1, and the biological half-lives of d- and l-isomer were 24 hr and 15 hr, respectively.