Controlled-Release Hormone Delivery Systems for Long-term Fertility Control: The Missing Dimension

Viewed in retrospect, the development of hormonal methods of fertility control could be broadly divided into three main phases: (i) development of the oral contraceptive 'Pill based on synthetic ovarian steroid hormones; (ii) the demonstration that continuous oral administration of progestins in microdoses could effectively prevent an undesired pregnancy[1]; and (iii) the development of sustained-release technology engendered by observations that steroid hormones diffuse at relatively constant rates throughbiocompatible polymeric rubber membrane, poly-dimethyl-siloxane (Silastic) [2]. The concept of controlled-release hormonal contraception is, due to the need to have a method of fertility control with minimal hormonal intervention. The development of controlled release contraceptive technology, though evolved out of serendipitous pursuit rather than approaches based on inductive physiological reasoning, has reached incredible levels of sophistication leading to the development of quite a good number of long-acting contraceptives such as silastic progestin implants, intravaginal rings releasing progestin, hormone-releasing biodegradable particulate delivery systems (microspheres and microcapsules), and so on. Many of these systems are either already in use or in advanced stages of clinical evaluation.