Jeremy C. Wright

An in vivo/in vitro comparison with a leuprolide osmotic implant for the treatment of prostate cancer

An osmotically driven implantable system was designed and characterized for the delivery of leuprolide over a year-long duration. Leuprolide has been used in the treatment of prostate cancer since the 1980s. The DUROS implant consists of a titanium alloy cylinder, measures 4 mm in diameter by 45 mm in length and holds approximately 150 microl of formulation. Stability studies indicated that leuprolide was stable, as a solution formulation in DMSO, for several years at 37 degrees C. In vitro release rate testing, at weekly intervals, showed zero-order delivery for 1 year. DUROS implants demonstrated release rates that were reproducible and similar to one another after storage at 25 degrees C for 18 months prior to testing. In vivo studies, with implants placed subcutaneously, revealed delivery rates comparable to those observed under in vitro conditions. Leuprolide stability was also comparable between in vivo and in vitro conditions. Steady leuprolide serum levels produced by the implant resulted in the desired pharmacodynamic efficacy endpoint of testosterone suppression, both in canines and in humans. The good agreement between in vivo/in vitro delivery rates was as expected for a delivery system based on the principles of osmosis.

Evolution of implantable and insertable drug delivery systems.

The paper describes the development of implantable and insertable drug delivery systems (IDDS) from their early stage in the 1960s until the current stage in the 2010s. It gives a detailed summary of non-degradable and biodegradable systems and their applications in different areas such as vascular disease treatment, birth control, cancer treatment, and eye disease treatment. It also describes the development of various implantable pump systems and some other atypical IDDS, the challenges and the future of IDDS.

The in vitro and in vivo performance of an osmotically controlled delivery system : IVOMEC SR® bolus

The IVOMEC SR® (sustained release) bolus is an osmotically driven drug delivery system designed for the long-term delivery to cattle of the antiparasitic drug, ivermectin. The bolus is administered orally by means of a balling gun and the weight of the bolus keeps it in the reticulum/rumen for the lifetime of the animal. The onset of delivery is immediate upon placement in the rumen and effective doses are delivered within the first week following administration. The steady-state delivery rate of approximately 12 mg/day of ivermectin is maintained for a period of approximately 135 days, after which, delivery ceases quickly. This duration is sufficient to provide season-long delivery of drug to grazing cattle.

DUROS® Osmotic Implant for the Delivery of Peptides and Proteins

An increasing number of pharmaceutically active peptides and proteins require a simple system for delivery to the ambulatory patient. The DUROS® implant (Figure 1) has been developed to address this need.