In many therapeutic applications it would be advantageous to deliver orally-administered drug into the systemic circulation some time after swallowing the formulation. Examples include the treatment of nocturnal asthma and prevention of secondary serious arrhythmias provoked by postural changes following previous severe cardiac ischemia. Many physiological and pathophysiological events have a circadian rhythm which suggests that treatment could be optimized by delivering the drug at the most appropriate time. By delaying the release of the drug until a programmed interval after swallowing, more sophisticated and efficient therapies can be designed.