I've been taking hiprex twice daily and i feel a uti coming on, i've started on alprim, do i stop hiprex whilst on alprim? thanks kindly

Probably stop it...: ...but check with your doctor. Also ask whether trimethoprim (Alprim) is the best antibiotic at this point. It's somewhat unusual treatment for UTI; trimethoprim plus sulfamethoxazole (e.g. Bactrim) usually is preferred. (However, I'm not familar with usual practice in Australia). In any case, your doctor may want a urine culture to know the exact bacteria and best antibiotic. Good luck!