Disclosed are oral osmotic dosage forms and methods wherein a semipermeable membrane of the oral osmotic dosage form includes from about 23 wt% to about 50 wt% of a flux enhancer and from about 0.01 wt% to about 5 wt% of antioxidant, based on the total dry weight of the semi-permeable membrane. Such compositions provide high flux membranes with improved mechanical and transport stability during storage on the shelf.