Overview PK/PD Comparison of Guanfacine ER and IR Status: Completed Trial end date: 2016-12-01 Target enrollment: Participant gender: Summary Evaluate whether a 4mg/day or 6/mg day dose of extended-release guanfacine produces pharmacokinetic/dynamic (PK/PD) properties similar to 3mg/day immediate release guanfacine. Phase: Phase 2 Details Lead Sponsor: Yale UniversityCollaborator: National Institute on Drug Abuse (NIDA)Treatments: Guanfacine