The invention is related to the development of an economical and safe drug delivery system for the delivery of insulin, insulin analogues, derivatives or combination thereof wherein a cartridge is configured to deliver more than 3 ml of the pharmaceutical composition of insulin, insulin analogues, derivatives or combination thereof from a pen type injector containing a cartridge of greater than 3 ml. Use of higher size of cartridge than the conventional 3 ml cartridge may ensure delivery of more number of doses of the insulin(s) and also may result in extending the use of same device for more number of days.
