Factors such as need for long-term treatment, narrow therapeutic window, complex dosing schedule, combination therapy, individualized or emergency dosing regimen, and labile active agents are presently outside of the capabilities of conventional drug administration.1 Drug delivery systems such as tablets or injections typically result in a drug delivery profile marked by an initial sharp increase in concentration above the therapeutic range, followed by a relatively rapid decrease into the non-therapeutic range.2 Thus, the drug concentration remains within the therapeutic range for a very short period of time, often too short, necessitating subsequent administration. In the case of potent drugs, a concentration signifi-

cantly above the therapeutic level could induce toxicity leading to serous clinical complications. In other circumstances, such as the case of administered antibiotics, a minimum concentration must be maintained for an extended period. If the antibiotic concentration falls below the acceptable therapeutic level, the intended therapeutic effect is not reached.