Metronidazole and clindamycin are both antibiotics but have differences in their method of action, their side effects and in the types of infection they normally treat. Although both are antibiotics, metronidazole is effective for infections caused by anaerobic bacteria and various parasitic protozoans. Clindamycin is effective for both aerobic and anaerobic bacterial infections and the protozoan that causes malaria. Metronidazole interferes with certain cellular functions, causing the death of the bacteria or parasites. Clindamycin does not kill the bacteria, rather it stops them from reproducing.
Both medications are available in oral and topical forms. Metronidazole comes in tablets, capsules, cream, lotion, gel and injectable forms. In addition to these forms, clindamycin also comes in an oral suspension, a topical foam and in a solution for acne treatment. Combinations of clindamycin and other medications are also used for acne treatment.
Clindamycin is prescribed for severe bacterial infections. This antibiotic treats infections of the skin, blood, internal organs and other infections. Clindamycin is also used for dental infections or to prevent infections of the heart in certain patients undergoing dental procedures. Metronidazole fights anaerobic bacterial infections in the lungs, intestines, joints and digestive organs. In addition, it is used to treat diseases caused by protozoans such as amoeba and Giardia.
The side effects of metronidazole and clindamycin have some similarities, but also several important differences. All antibiotics can cause an upset in the beneficial bacterial flora of the intestines. This can lead to diarrhea and intestinal cramps. Clindamycin, though, has been linked to a severe intestinal condition caused by drug resistant bacteria. An overgrowth of resistant bacteria during and after treatment can lead to a potentially lethal condition in rare instances.
Both metronidazole and clindamycin commonly cause mild diarrhea, nausea and vomiting. Metronidazole’s side effects are exacerbated with the use of alcohol and may result in a severe hangover. Other common side effects of metronidazole include a metallic taste in the mouth, headache and loss of appetite. People should not lie down immediately after taking clindamycin as nausea, heartburn or diarrhea may result. It is advised that patients tell their healthcare providers of any unusual or severe symptoms while taking either medication.
At least one study concluded that metronidazole and clindamycin exhibited differences in bacterial resistance during treatment of bacterial vaginosis in women. Both study groups used a vaginal preparation of either metronidazole or clindamycin. Researchers found there was significantly more bacterial resistance to clindamycin in women treated for bacterial vaginosis, especially after the course of treatment. There was a very low incidence of bacterial resistance to metronidazole. They found an increase in Escherichia coli concentrations in the group treated with clindamycin but an increase in beneficial Lactobacillus in women treated with metronidazole after the treatment was over.