The present systems combines a drug delivery catheter and a dilator apparatus for use in lysing of clots wherein an internal dilator has a central lumen and an outer catheter is arranged coaxially about said internal dilator. An annular space for fluid passage is sealingly formed between an outer wall of the internal dilator and an inner wall of the outer infusion catheter. Apertures are located in the outer wall of the outer catheter for distributing fluid from the annular space. The internal dilator has a tip element and the outer catheter has an end opening so that together the end opening is occluded by the tip element which protrudes beyond the outer catheter when the outer catheter is arranged coaxially about the internal dilator and additionally the internal dilator is removable from the outer catheter to enable the introduction of a larger guide wire for further medical procedures.