3 weeks of septrin for a cystitis infection is the norm i think...the drug has to have time to penetrate the area, build up concentration and then retain that concentration level for at least two weeks - hence three weeks ..
Septrin is recommended for UTi's over baytril -
a) it has better penetrating power to ge through the blood to the bladder
b) itis much more effective against the type of bugs normally responsile for UTI;s than baytril
HTH and hope Gertie gets better soon
PS - sorry if I'm sounding repetitive to other forum users....but I have found- pearl barley water (from home-made boiled pearl barley 50-60mins and then seived) and cranberry is very effective at assisting with alleviating symptoms..(2ml 3-4x daily).whether it is caused by a bug or is "sterile" cystitis....
xx