Studies on Pharmacokinetics of LHRH Analogues After Different Modes of Administration

The LHRH agonist analogues have become valuable tools for endocrine investigations of reproductive functions. They are established drugs for therapy of reproductive disorders and assisted reproduction.24,25 LHRH agonists have a selective antigonadotropic action and suppress ovarian and testicular function in a reversible manner. In the control of gonadal steroid secretion, in reproductive disorders, and in oncology (prostate carcinoma and premenopausal mammary carcinoma), LHRH agonists have acquired an important therapeutic role. This is in part due to the fact that their action on gonadotropins and gonadal steroids is highly selective, with no side effects on the secretion of other hormones or on other organ systems.24,25,31 To take full advantage of the clinical potential, different modes of administration are required for short-term use (injections), long-term use by self-medication (nasal spray formulations), and long-term use by injection of sustained release preparations. In gynaecology, nasal spray therapy has been investigated for contraception, endometriosis, leiomyoma uteri and other oestrogen-dependent conditions. More recendy, long acting implants and microcapsules have been introduced into oncology, e.g. for adjuvant therapy of premenopausal mammary carcinoma. In this review, the pharmacokinetics of the different dosage forms will be discussed with reference to particular clinical indications, and the metabolism of LHRH agonists in experimental animals and in the human will be reported.