A self-puncturing liquid drug cartridge (310; 410) configured to be used with an inhaler, comprising: a container (318; 418) configured to store a liquid drug; a septum (320, 432) configured to seal a first end of the container (318; 418); a needle assembly (314, 434) coupled to the first end of the container (318; 418), the needle assembly (314, 434) including a hollow needle (316, 436) and being reconfigurable between a first configuration in which the hollow needle (316, 436) does not extend through the septum (320, 432) and a second configuration in which the hollow needle (316, 436) extends through the septum (320, 432) so as to establish a fluid path for ejection of the liquid drug from the container of the cartridge (310; 410) for aerosolization by an inhaler; and a piston (322, 420) sealing a second end of the container (318; 418), the piston (322, 420) being repositionable relative to the container (318; 418) so as to selectively eject a volume of the liquid drug from container (318; 418) via the hollow needle (316, 436) whereby the hollow needle (316, 436) has an exposed end that is not sharpened and has a sharpened end that is directed towards the septum (320, 432) and characterised in that the needle assembly (314, 434) further comprises: a cap (324, 438) that is configured to receive and retain first end portion of the container (318; 418); a guide element (326, 440) including a receptacle configured to slidingly receive and interface with the cap (324, 438) and a portion of the container (318; 418); and a spring (328, 442) that is coupled with a distal side of the cap (324, 438), wherein when the needle assembly (314, 434) is in the first configuration the spring (328, 442) is in an un-deflected configuration and disposes the sharpened end of the hollow needle (316, 436) within a body of the cap (324, 438) such that the sharpened end of the hollow needle (316, 436) does not extend through the septum (320, 432) and when the needle assembly (314, 434) is in the second configuration the guide element (326, 440) is in contact with a shelf of the inhaler, and the container (318; 418) has been pushed towards the guide element (326, 440), thereby partially compressing the spring (328, 442) and inserting the sharpened end of the hollow needle (316, 436) through the septum (320, 432). a container (318; 418) configured to store a liquid drug; a septum (320, 432) configured to seal a first end of the container (318; 418); a needle assembly (314, 434) coupled to the first end of the container (318; 418), the needle assembly (314, 434) including a hollow needle (316, 436) and being reconfigurable between a first configuration in which the hollow needle (316, 436) does not extend through the septum (320, 432) and a second configuration in which the hollow needle (316, 436) extends through the septum (320, 432) so as to establish a fluid path for ejection of the liquid drug from the container of the cartridge (310; 410) for aerosolization by an inhaler; and a piston (322, 420) sealing a second end of the container (318; 418), the piston (322, 420) being repositionable relative to the container (318; 418) so as to selectively eject a volume of the liquid drug from container (318; 418) via the hollow needle (316, 436) whereby the hollow needle (316, 436) has an exposed end that is not sharpened and has a sharpened end that is directed towards the septum (320, 432) and characterised in that the needle assembly (314, 434) further comprises: a cap (324, 438) that is configured to receive and retain first end portion of the container (318; 418); a guide element (326, 440) including a receptacle configured to slidingly receive and interface with the cap (324, 438) and a portion of the container (318; 418); and a spring (328, 442) that is coupled with a distal side of the cap (324, 438), wherein when the needle assembly (314, 434) is in the first configuration the spring (328, 442) is in an un-deflected configuration and disposes the sharpened end of the hollow needle (316, 436) within a body of the cap (324, 438) such that the sharpened end of the hollow needle (316, 436) does not extend through the septum (320, 432) and when the needle assembly (314, 434) is in the second configuration the guide element (326, 440) is in contact with a shelf of the inhaler, and the container (318; 418) has been pushed towards the guide element (326, 440), thereby partially compressing the spring (328, 442) and inserting the sharpened end of the hollow needle (316, 436) through the septum (320, 432). a cap (324, 438) that is configured to receive and retain first end portion of the container (318; 418); a guide element (326, 440) including a receptacle configured to slidingly receive and interface with the cap (324, 438) and a portion of the container (318; 418); and a spring (328, 442) that is coupled with a distal side of the cap (324, 438), wherein when the needle assembly (314, 434) is in the first configuration the spring (328, 442) is in an un-deflected configuration and disposes the sharpened end of the hollow needle (316, 436) within a body of the cap (324, 438) such that the sharpened end of the hollow needle (316, 436) does not extend through the septum (320, 432) and when the needle assembly (314, 434) is in the second configuration the guide element (326, 440) is in contact with a shelf of the inhaler, and the container (318; 418) has been pushed towards the guide element (326, 440), thereby partially compressing the spring (328, 442) and inserting the sharpened end of the hollow needle (316, 436) through the septum (320, 432).