Adverse Reactions In two multicenter clinical trials, total of 270 patients received 750 mg Flagyl ER tablets orally once daily for days, flagyl hcl tablete and 287 were treated with comparator agent administered intravaginally once daily for days. It should not be understood to indicate that the use of Generic for Flagyl is safe, appropriate or effective for you. Anaerobic Bacterial Infections In the treatment of most serious anaerobic infections, Flagyl. Kidney function, potassium blood level should be performed periodically to monitor your progress or check for side effects. Clindamycin or Cleocin Clindamycin ointment is applied intravaginally before going to sleep, for one week.