A container 900 for containing a coupling medium for transdermal delivery of a medicament using a transducer unit having a transducer 108 with an output face 110. Container 900 comprises chamber 914 for receiving a coupling medium and a contact surface 212 for contacting the transducer output face 110. Container 900 is attachable to the transducer unit and upon attachment forms an acoustic coupling between the transducer output face 110 and contact surface 212 for ultrasound transmission. Attaching container 900 to transducer 108 may form an air free coupling between the transducer output face 110 and contact surface 212, where contact surface 212 may be deformable to conform to the transducer output face 110. Contact surface 212 may comprise a surface of contact membrane that is impedance matched to the coupling medium. Container 900 may comprise a reservoir 950 external to chamber 914 for holding the coupling medium and a transfer means 956 for transferring the coupling medium to the chamber 914 where transfer means 956 may comprise a piston disposed in the reservoir and where container 900 or the transducer unit may comprises skin contact detection means. Also disclosed a medicament delivery device for transdermal delivery of a medicament.
