Most common antibiotic given for bladder infection?

Depends.: Depends upon who you ask. Various specialty groups make different recommendations, local resistance patterns and patient characteristics may modify the choice. Top three are probably nitrofurantoin, Ciprofloxacin or levofloxacin, and septra (sulfamethoxazole and trimethoprim). All are potentially good choices. But there are many other good choices. If culture is done antibiotics may be tailored.