Metronidazol

Metronidazol is a nitroimidazole antimicrobial used to treat infections caused by anaerobic bacteria and certain protozoa. It is typically bactericidal, acting after intracellular reduction to active metabolites that damage microbial DNA. It is effective against most anaerobic Gram-positive and Gram-negative organisms and against protozoa such as Giardia lamblia, Entamoeba histolytica, and Trichomonas vaginalis. It has little activity against aerobic bacteria.

Indications include intra-abdominal and gynecologic infections, pelvic inflammatory disease, bacterial vaginosis, and prophylaxis in some colorectal surgeries. It is also used for protozoal infections and, in combination regimens, as part of Helicobacter pylori eradication therapy. Metronidazol can be given orally or by intravenous injection; topical forms are available for skin and vaginal infections.

Pharmacokinetics and administration: Metronidazol is well absorbed from the gastrointestinal tract when taken by mouth and distributes widely in body tissues and fluids. It is extensively metabolized in the liver and has a half-life of about 6 to 8 hours in healthy adults; excretion is primarily via the kidneys. Dose adjustments may be necessary in significant liver impairment.

Adverse effects and interactions: Common side effects include nausea, a metallic taste, loss of appetite, and headache. Less frequent but serious events include neuropathy, ataxia, seizures, and leukopenia, especially with long-term use. A disulfiram-like reaction can occur with alcohol consumption during or shortly after therapy; avoid alcohol during treatment and for at least 48 hours after. Metronidazol can interact with warfarin, phenytoin, phenobarbital, and cimetidine, potentially altering drug levels. Pregnancy safety is context-dependent; generally, use in the first trimester is avoided unless clearly indicated. Breastfeeding may be discouraged, as the drug is excreted in breast milk.

Notes: Resistance exists in some anaerobes; clinical response should guide duration and dosing.