Thanks for your query.Based on the facts that you have posted it appears that you have undergone major spinal surgery
.You have not mentioned the reason or disease for which you have undergone this surgery.
In majority of cases bladder problem developing after spinal surgery are due to damage to the nerve
supplying bladder muscles.called as (Neurogenic Bladder
It takes long time for bladder to regain tone and strength to pump the urine to initiate urination.
The role of medicine that you have mentioned is very limited in your case..
You have to continue with clean self intermittent catheterization (CSIC) till your bladder regains its tone.
Please take care to avoid getting UTI.