A drug delivery device includes a catheter having first and second ends； a flexible membrane having a rim securely connected to an inner surface of the catheter to define a first volume between the first end and the flexible membrane, and a second volume between the flexible membrane and the second end, such that the second volume is substantially the same as a desired drug volume； and a pressurizable member coupled to the catheter for operably delivering a drug. In use, a desired volume of the drug is preloaded into the second volume of the catheter that in turn is slid into a guidance device, when the guidance device is placed in a target of interest, the pressurizable member applies a pressure into the first volume to exert a force upon the flexible membrane to operably squeeze the second volume, thereby unloading the drug into the target.
