sustainedrelease

Sustained-release (SR) refers to dosage forms that release a drug at a predetermined rate over an extended period, maintaining therapeutic levels while reducing dosing frequency. SR aims to smooth plasma concentration fluctuations and is often contrasted with immediate-release formulations. The terms sustained-release, extended-release (ER), and controlled-release (CR) are sometimes used interchangeably, but vary in emphasis on duration and release profile.

Mechanisms and technologies: SR can be achieved by matrix systems (drug dispersed in a polymer matrix), reservoir systems with a rate-limiting coating, diffusion-controlled or erosion-controlled matrices, osmotic systems, and multiparticulates such as coated beads or microspheres. Oral SR products may be tablets, capsules, or beads; other routes include transdermal patches and depot injections that release over weeks to months.

Advantages and challenges: Benefits include reduced dosing frequency, steadier drug exposure, and improved adherence. Challenges include variability due to stomach pH and transit time, potential dose-dumping if the system is damaged, limited suitability for drugs with very short half-lives or narrow therapeutic ranges, and higher manufacturing costs.

Applications and regulation: SR formulations are common for chronic therapies such as analgesics, antihypertensives, and hormones. Regulatory oversight requires demonstration of a consistent release profile, appropriate bioavailability data, and clear labeling for dosing, storage, and handling.