Implants:
Implantable implants are solid or semi-solid devices containing the drug, designed to release the therapeutic agent at a controlled rate.
They can be biodegradable or non-biodegradable, depending on the application and desired duration of drug release.
Types of Implants
Reservoir Implants:
Structure: Contain a drug core surrounded by a rate-controlling membrane.
Mechanism: Drug diffuses through the membrane at a controlled rate.
Example: Norplant (levonorgestrel contraceptive implant).
Matrix Implants:
Structure: Drug is uniformly dispersed within a polymer matrix.
Mechanism: Controlled by drug diffusion and matrix erosion or degradation.
Example: Implants using poly(lactic-co-glycolic acid) (PLGA) for sustained drug release.
Biodegradable Implants:
Structure: Designed to degrade within the body after drug release.
Mechanism: Drug is released as the polymer matrix breaks down.
Example: Gliadel wafers for brain cancer treatment.
Non-Biodegradable Implants:
Structure: Remain intact in the body after drug release.
Mechanism: Require surgical removal after the drug is depleted.
Example: Silicone-based hormone implants.
Advantages
Controlled Release: Sustained, steady drug release.
Improved Compliance: Less frequent dosing.
Targeted Delivery: Localized therapy with fewer side effects.
Reduced Adverse Effects: Consistent drug levels.
Long-term Therapy: Suitable for chronic conditions.
Disadvantages
Surgical Requirement: Implantation and removal may need minor surgery.
Infection Risk: Potential irritation or infection at the implant site.
Drug Limitations: Not all drugs are suitable.
Cost: More expensive than conventional forms.
Dose Adjustment Limitations: Hard to adjust doses post-implantation.
Applications
Hormone Therapy: Consistent hormone delivery, e.g., contraceptive implants.
Chronic Pain: Continuous pain relief.
Psychiatric Disorders: Steady medication release.
Cancer Treatment: Direct delivery to tumors.
Diabetes Management: Continuous insulin release for stable glucose control.