Metronidazole (Flagyl)

Metronidazole is an antibiotic that fights bacteria in your body. It is used to treat bacterial infections of the vagina, stomach, skin, joints, and respiratory tract.

Therapeutic actions:
Metronidazole is amebicidal, bactericidal, and trichomonicidal. Unionized metronidazole is readily taken up by anaerobic organisms and cells. Its selectivity for anaerobic bacteria is a result of the ability of these organisms to reduce metronidazole to its active form intracellularly. The electron transport proteins necessary for this reaction are found only in anaerobic bacteria. Reduced metronidazole then disrupts DNA's helical structure, thereby inhibiting bacterial nucleic acid synthesis. This eventually results in bacterial cell death. Metronidazole is equally effective against dividing and nondividing cells.
Because of its mechanism of action, low molecular weight, and limited binding to serum proteins, metronidazole is a highly lethal antimicrobial. Resistance to metronidazole is almost nonexistent. Metronidazole's spectrum of activity includes protozoa and obligate anaerobes including: Bacteroides group (including B. fragilis), Fusobacterium, Veillonella, the Clostridium group (including C. difficile and C. perfringens), Eubacterium, Peptococcus, and Peptostreptococcus. It is effective against B. fragilis isolates that are resistant to clindamycin. It is not effective against the common aerobes but is active against the aerobe Gardnerella (Haemophilus) vaginalis. The protozoan coverage of metronidazole includes Entamoeba histolytica, Giardia lamblia, and Trichomonas vaginalis Metronidazole also has immunosuppressive and antiinflammatory actions, and it has been used in patients with rosacea. The antimicrobial actions of metronidazole alter the bacterial metabolism of bile acids in the GI tract, decreasing pruritus in patients with cholestasis secondary to primary biliary cirrhosis.

What is it used for?:
• Symptomatic Trichomoniasis;
• Asymptomatic Trichomoniasis;
• Asymptomatic Consorts.
• Amebiasis;
• Anaerobic Bacterial Infections:
• INTRA-ABDOMINAL INFECTIONS, including peritonitis, intra-abdominal abscess, and liver abscess;
• SKIN AND SKIN STRUCTURE INFECTIONS;
• GYNECOLOGIC INFECTIONS, including endo-metritis, endomyometritis, tubo-ovarian abscess, and postsurgical vaginal cuff infection;
• BACTERIAL SEPTICEMIA;.
• BONE AND JOINT INFECTIONS, as adjunctive therapy;
• CENTRAL NERVOUS SYSTEM (CNS) INFECTIONS, including meningitis and brain abscess;
• LOWER RESPIRATORY TRACT INFECTIONS, including pneumonia, empyema, and lung abscess;
• ENDOCARDITIS.

Contraindications and cautions:
• allergy to any ingredient in Flagyl or to other nitroimidazoles (eg, tinidazole);
• the first 3 months of pregnancy;
• taking busulfan, an ergot alkaloid (eg, ergotamine), or intaken of disulfiram within the past 2 weeks;
• taking an HIV protease inhibitor that contains alcohol (eg, amprenavir solution); check with your pharmacist if you are unsure if the medicine contains alcohol
• alcohol.

Side effects:
appetite loss; constipation; diarrhea; dizziness; headache; metallic taste; nausea; stomach upset; vomiting.

Interactions:
• Flagyl 's effectiveness may be decreased by barbiturates (eg, phenobarbital) or phenytoin;
• Flagyl may increase the risk of side effects of anticoagulants (eg, warfarin), busulfan, ergot alkaloids (eg, ergotamine), HIV protease inhibitors containing alcohol (eg, amprenavir solution), lithium, or macrolide immunosuppressants (eg, tacrolimus);
• Disulfiram because side effects, such as mental or mood changes, may occur
• Flagyl may decrease effectiveness of oral contraceptives (eg, birth control pills).