From the Guidelines
Metronidazole and levofloxacin can be taken together for specific infections, as recommended by the Infectious Diseases Society of America in their 2014 guidelines 1. This combination is commonly used to treat mixed bacterial infections, particularly those involving both aerobic bacteria (targeted by levofloxacin) and anaerobic bacteria (targeted by metronidazole). For example, this combination might be prescribed for complicated intra-abdominal infections, pelvic inflammatory disease, or certain skin and soft tissue infections, as seen in the guidelines for the diagnosis and management of skin and soft tissue infections 1. When taking these medications together, it's essential to follow your doctor's specific dosing instructions and complete the full course of both antibiotics. You may experience side effects including nausea, diarrhea, headache, or dizziness. While taking metronidazole, you must avoid alcohol completely as it can cause severe reactions including flushing, headache, nausea, and vomiting. Both medications can increase the risk of tendon damage, particularly in older adults or those taking corticosteroids, so report any unusual joint or tendon pain immediately. These medications work through different mechanisms - levofloxacin inhibits bacterial DNA synthesis while metronidazole disrupts DNA in anaerobic organisms - making them effective complementary agents for mixed infections. Some key points to consider when taking metronidazole and levofloxacin together include:
- Following the prescribed dosing regimen
- Completing the full course of treatment
- Avoiding alcohol consumption
- Monitoring for potential side effects, such as tendon damage
- Reporting any unusual symptoms to your healthcare provider.
From the Research
Metronidazole and Levofloxacin Combination
- The combination of metronidazole and levofloxacin has been studied in various research papers 2, 3, 4, 5.
- A study published in 2005 found that levofloxacin plus metronidazole administered once daily exhibited activity similar to that of moxifloxacin against a mixed infection of Escherichia coli and Bacteroides fragilis in an in vitro pharmacodynamic model 2.
- Another study from 1988 found that high metronidazole concentrations did not affect the bactericidal efficacy of ciprofloxacin (a fluoroquinolone similar to levofloxacin) on aerobic and anaerobic pathogens, and the combination of ciprofloxacin and metronidazole was slightly more potent against certain anaerobic pathogens than either drug alone 3.
- A pharmacokinetic and pharmacodynamic study from 2004 found that the combination of intravenous levofloxacin and metronidazole was well tolerated and had greater area under the inhibitory and bactericidal curves than levofloxacin alone against certain bacterial strains 4.
- A study from 2000 found that the combination of levofloxacin with metronidazole led to synergy in time-kill tests against certain anaerobic strains 5.
Pharmacokinetics and Pharmacodynamics
- The pharmacokinetics and pharmacodynamics of levofloxacin and metronidazole have been studied in healthy adult subjects 4.
- The study found that the mean concentrations of levofloxacin were not different between study periods and were similar to those previously published 4.
- The area under the concentration-time curve/MIC ratios for levofloxacin and metronidazole were determined against clinical isolates of Bacteroides fragilis, Bacteroides thetaiotaomicron, Peptostreptococcus asaccharolyticus, and Escherichia coli 4.
Clinical Implications
- The combination of metronidazole and levofloxacin may be useful for the treatment of mixed aerobic/anaerobic infections 2, 3, 4, 5.
- The choice of fluoroquinolone, including levofloxacin, should be based on the anticipated organisms and evaluation of risk factors for specific pathogens, as well as pharmacokinetic parameters such as peak concentration and area under the concentration-time curve 6.