Potential new drug delivery systems for antidepressants: an overview

Oral administration is probably a nonoptimal delivery system for most psychotropics. Scientists are turning to optimizing drug delivery as a method for enhancing antidepressant response. Advances in oral drug delivery have come in the form of sustained-release formulations of antidepressants, which have smoothed the plasma drug concentration maxima and minima, thus decreasing side effects and increasing tolerability. The future of pharmacologic treatment for psychiatric disorders may be in part dependent on nonoral drug delivery systems such as implantable and transdermal delivery systems. Like the available sustained-release formulations of antidepressants, these alternative delivery systems will have enhanced safety, tolerability, and efficacy because of their ability to maintain a more constant circulating drug level. Implantable devices that sense, stimulate, deliver to, and record from biological systems are being developed through microtechnology and nanotechnology. Transdermal delivery techniques, such as passive diffusion, sonophoresis, electroporation, and iontophoresis, enhance the skin's permeability to drugs. Iontophoresis appears to be a promising and perhaps the most efficient assisted-delivery technique for future antidepressant transdermal delivery.