Expandable reamers for enlarging boreholes in subterranean formations include a tubular body and at least one member positioned in openings in the tubular body. The at least one member is configured to move between retracted and extended positions. A push sleeve is disposed at least partially within the tubular body and coupled to the at least one member. The push sleeve moves axially upward to move the at least one member to the extended position in response to a pressure of drilling fluid passing through a drilling fluid flow path in the tubular body. The push sleeve moves axially downward to move the at least one member to the retracted position in response to a pressure of drilling fluid upon a restrictive element disposed within the fluid passageway. The restrictive element disposed within the fluid passageway may be discarded from the fluid passageway by increasing the flow rate through the drilling fluid flow path.