The effects of disodium cromoglycate on dexamethasome metabolism.

The effect of disodium cromoglycate on dexamethasone metabolism was studied in 4 patients with bronchial asthma before and after 3 weeks of treatment. Labeled dexamethasome was injected intravenously and serial blood samples were collected during the next 6 hours. Transport kinetics of labeled dexamethasone were determined using a 2-compartment model. Baseline plasma equilibrated half-life values ranged from 133 to 258 min, and metabolic clearance rate ranged from 134 to 912 liter per day. After disodium cromoglycate therapy a small decrease in labeled dexamethasone clearance occurred. There was a mean increase in half-life of 20 min (9 per cent), being 201+/-51 (mean +/- SD) before therapy and 220+/-57 min after therapy. This was not significant. Metabolic clearance rate decreased 13 per cent (59 liter per day), being 441+/-334 liter per day before and 382+/-304 liter per day after treatment (P less than 0.05). Other transport kinetics of labeled dexamethasone were not significantly different with therapy. The results of this investigation demonstrate that disodium cromoglycate produces small but probably not significant changes in dexamethasone metabolism. The investigation supports the thesis that the steroid-sparing effect of disodium cromoglycate is not the result of depression of corticosteroid plasma clearance with longer duration of steroid action but most likely is the result of the effect of disodium cromoglycate on cellular mechanisms and inhibition of mediator release.