A pharmaceutical answer to nonadherence: Once weekly oral memantine for Alzheimer's disease

Adherence to medication regimens is a major barrier to effective treatment in many disease areas, notably in dementia which causes cognitive impairment that reduces patients' awareness of non-adherence and their ability to manage medication. The development of oral dosage forms that can be infrequently dosed, and therefore improve adherence rate and facilitate direct observed therapy, has been a goal for decades. We describe the first demonstration of an oral formulation that achieves >7-day gastric retention and sustained pharmacokinetics in the challenging dog model. Gastric retention requires physical resistance of the dosage form to gastric emptying forces, which are known to be stronger in dogs than in humans, making successful gastric retention in dogs a stringent test for predicting human translatability. This formulation of memantine hydrochloride is the first oral dosage form that achieves multi-day drug release with near zero-order kinetics and efficient delivery. In the dog model, relative memantine bioavailability approaches 100% with sustained plasma levels of memantine over seven days and profiles that can be tuned by varying components of the formulation. A single gastric resident dosage form achieves an AUC equivalent to 7 daily treatments with the marketed daily capsule, with a Cmax that is no higher than the daily product. PK modeling predicts that the gastroretentive formulation will maintain therapeutic blood levels in humans when administered once weekly. The formulation methodology presented here is applicable to many water soluble drugs and may enable the development of long-acting oral therapies for a wide variety of conditions.