Pharmacology and Pharmacokinetics. The mechanism of action of Diclegis is unknown.1. Peak plasma concentrations of the doxylamine component occur in 7.5 hours, and the pyridoxine component, 5.5 hours. Elimination half-life is 12.5 hours for the doxylamine component, and in 0.5 hours for the pyridoxine component. Steady-state concentrations of doxylamine are reached within 24 to 48 hours. Pyridoxine does not reach steady-state concentrations due to its short half-life.1.