Development and validation of an ion-pair liquid chromatographic method for the quantitation of sodium cromoglycate in urine following inhalation.

An ion-pair liquid high-performance chromatography method with solid-phase extraction for measuring urinary concentrations of sodium cromoglycate following inhalation has been developed and validated. Sodium cromoglycate was extracted from urine on a 100-mg phenyl cartridge (Isolute, Jones Chromatography) and then quantified on a 25-cm C8 Spherisorb 5 microns stationary phase with a mobile phase of methanol-0.045 M phosphate buffer-0.05 M dodecyl triethyl ammonium phosphate (550:447.6:2.4, v/v) pH 2.3, at 0.85 ml min-1 using nedocromil sodium as an internal standard and UV detection at 238 nm. The inter- and intra-day reproducibilities were 8.33 and 13.63%, respectively, at 0.25 mg l-1. The limit of determination for sodium cromoglycate was 0.25 mg l-1 (with a signal-to-noise ratio of greater than 10:1). Following oral and inhaled administration of 20 mg of sodium cromoglycate to eight healthy volunteers, the mean and S.D. of sodium cromoglycate excreted in the urine at 0.5, 1 and 24 h post-dose were 0.02, 0.05 and 0.33%, and 0.16, 0.30 and 1.55% of the dose, respectively. The urinary recovery of sodium cromoglycate at 0.5 and 1 h following inhalation can therefore be used to compare the amount of drug reaching the respiratory tract using different sodium cromoglycate inhaled products or inhalation methods.