Polymeric sustained-release drug delivery implants are a good way to release drugs into the body over a long period of time, foregoing undesirable the need for dosing multiple times monthly or even daily. Implantable forms of sustained-release systems are the most effective for long-term release beyond three months.
Indications
One of the main drivers of the need for sustained-delivery methods is high risk of patient compliance. These are patient populations which are more prone to stopping their medication when it should be taken once daily, such as patients with memory disorders. This can also put a strain on physicians which may need to be present to help a patient take their medication. Therefore, implantable drug delivery can help ease this workload.
Furthermore, implantable systems hold promise for targeted drug delivery. Placing an implant close to where the drug needs to be delivered, for instance near a tumour, can be an effective method for targeting that site. Some drugs may also have bioavailability challenges which can be circumvented by encapsulating the therapy within a polymeric matrix.
Ideal drug candidates should have a molecular weight below 1000 and be potent enough to allow for effective delivery in microgram doses.
Polymer Selection
There are two types of this class of delivery systems: bioresorbable polymers that break down in the body which are better for shorter release (1-6 months), or biodurable polymers that stay delivering drugs in the body for sometimes multiple years.
For bioresorbable products, polymers like PLGA, PCL, and PEG are all well established materials. Silicone and EVA are common polymers used for biodurable products. Most products are designed primarily for drug delivery, often in rod shapes, using single entity systems or membrane applications to control release rates.
Manufacturing
Traditional manufacturing methods, including extrusion and moulding, are used to create these delivery systems, with considerations for drug form and release rates. The presentation also addresses the need for faster drug release and alternative manufacturing approaches to accommodate various drug forms and applications.
