Systems, devices, and methods for transdermal delivery of one or more therapeutic active agents to a biological interface. An iontophoretic drug delivery system is provided for transdermal delivery of one or more therapeutic active agents to a biological interface of a subject. The iontophoretic drug delivery system includes at least one active agent reservoir. The one or more active agent reservoirs are loadable with a vehicle for transporting, delivering, encapsulating, and/or carrying the one or more active agents