Biodegradable implants sized and suitable for implantation in an ocular region or site and methods for treating ocular conditions. The implants provide an extended release of an active agent at a therapeutically effective amount for a period of time between 10 days and one year or longer. The biocompatible, injectable intraocular drug delivery system comprises a plurality of microspheres in aqueous medium and an alpha Z adrenergic agonist such as brimonidine and biodegradable polyactic acid (PLA) polymers.
