Implant (Drug Delivery)
A device surgically placed under the skin to provide continuous, long-term peptide release. Histrelin implant delivers GnRH agonist for 12 months, and goserelin implant releases drug over 1-3 months. Implants eliminate the need for frequent injections and ensure consistent drug levels.
Technical Context
Histrelin implant (Vantas for prostate cancer, Supprelin LA for precocious puberty) is a small flexible cylinder (~3cm × 3mm) containing 50mg histrelin in a hydrogel matrix, placed subcutaneously in the upper arm via minor surgical procedure. It provides constant histrelin release for 12 months. Goserelin implant (Zoladex) is a PLGA biodegradable cylinder (~1mm diameter × 1cm length for 1-month, larger for 3-month) injected subcutaneously in the anterior abdominal wall using a large-bore needle device. The PLGA matrix gradually erodes, releasing goserelin. Implants provide the best adherence of any dosing form (100% after placement) and the most consistent drug levels. Disadvantages: need for clinical procedure, potential insertion-site complications, and inability to immediately discontinue treatment.