Implantable systems and microparticle depots are used in many areas of drug delivery to release medicines at a controlled rate within the body. The use of these long-acting dosage forms eliminates the need for frequent administrations via traditional routes of administration, which ensures patient compliance and results in improved outcomes. Dr Kimberly Zubris and Jite Okoh discuss the benefits these long-acting products bring to drug delivery and address the critical design, manufacturing and testing challenges that should be considered in their development.