Positives

• One patient reported that after months of being unexplainably sick and losing weight, they felt better the day after starting Flagyl and that subsequent flares responded within 4 hours, per Drugs.com Flagyl reviews.
  
  
• Eradication studies show 79% of SIBO patients cleared the infection on metronidazole, with strong methane reduction in particular, per a PubMed systematic review.
  
  

Negatives

• One SIBO patient described moderate side effects so unpleasant they stopped Flagyl after 4 days and switched back to rifaximin, per the Drugs.com patient reviews.
  
  
• About 41% of metronidazole patients described nausea, headache, and a metallic taste, with the antibiotic carrying higher GI side effects than alternatives in a ScienceDirect comparative study.
  
  

Hurdles & Side Effects

• Patients must completely avoid alcohol during and several days after treatment because of severe disulfiram-like reactions including vomiting and pounding heartbeat, per NHS metronidazole side effects guidance.
  
  
• Long courses or repeat rounds raise concern for peripheral neuropathy, which patients describe as new burning or numbness in hands and feet, per Cleveland Clinic's metronidazole monograph.