Can Nitrofurantoin Be Taken By Renal Impaired Patients?

Hi, my mom (63), got ESRD (non-dialysis), creatinine 5.1, mom got repeated UTI and last time doctor gave 500 mg meropenem IV (BD dose) for 10 days, after that her colony count was reduced, from 10^6 to 10^4 and then doc prescribed 50 mg nitrofurantoin once daily for a month, someone told me nitrofurantoin is toxic for renal impaired patients, so should we carry on with the dose? we are trying to avoid dialysis as long as possible, she got no edema, no diabetes and swingling blood pressure. Please suggest. Thanks