TINIDAZOLE
Clinical safety rating: safe
Animal studies have demonstrated safety
Tinidazole is a nitroimidazole antibiotic that diffuses into microorganisms where it is reduced by bacterial nitroreductases to form reactive cytotoxic intermediates that damage DNA and inhibit protein synthesis, leading to cell death. It is active against anaerobic bacteria and protozoa.
| Metabolism | Tinidazole is metabolized primarily in the liver via oxidation and glucuronidation. The major metabolic pathways involve CYP450 enzymes, mainly CYP3A4, with minor contributions from other isoforms. |
| Excretion | Following oral administration, approximately 20-25% of the dose is excreted unchanged in urine, with an additional 10-15% as metabolites. Fecal excretion accounts for about 50% of the dose, primarily as metabolites. Biliary excretion is a minor route. |
| Half-life | The terminal elimination half-life is approximately 12-14 hours in healthy adults, which supports once-daily dosing. In hepatic impairment, half-life may be prolonged. |
| Protein binding | Approximately 12-15% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | The apparent volume of distribution is approximately 0.9 L/kg, indicating extensive tissue distribution including penetration into genitourinary tissues, abscesses, and cerebrospinal fluid. |
| Bioavailability | Oral bioavailability is nearly 100% due to complete absorption from the gastrointestinal tract. |
| Onset of Action | Oral: Onset of clinical effect occurs within 2-4 hours after a single oral dose, with peak plasma concentrations reached at 1-2 hours. |
| Duration of Action | The duration of action is approximately 24 hours following a single oral dose, allowing for once-daily dosing. Clinical efficacy against susceptible organisms persists for at least 24 hours. |
2 g orally once daily for 2 days; alternatively, 1 g orally once daily for 5 days for trichomoniasis. For bacterial vaginosis: 2 g orally once daily for 2 days. For giardiasis: 2 g orally as a single dose. For amebiasis: 2 g orally once daily for 3 days for intestinal amebiasis; 2 g orally once daily for 5 days for hepatic amebiasis.
| Dosage form | TABLET |
| Renal impairment | For CrCl >60 mL/min: no adjustment. For CrCl 30-60 mL/min: no adjustment for single dose; for multiple doses, consider extending interval to every 48 hours. For CrCl <30 mL/min: use with caution; data insufficient for specific recommendations. Hemodialysis: administer after dialysis on dialysis days. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% or consider alternative therapy. Child-Pugh C: contraindicated or avoid use. |
| Pediatric use | For giardiasis: 50 mg/kg orally as a single dose (maximum 2 g). For amebiasis: 50 mg/kg orally once daily for 3 days (maximum 2 g per dose). For trichomoniasis: not recommended in children <12 years; for ≥12 years, same as adult dosing. |
| Geriatric use | No specific dose adjustment recommended; monitor for side effects due to potential age-related renal impairment. Use creatinine clearance to guide renal adjustment if needed. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Disulfiram-like reaction can occur with alcohol Can cause peripheral neuropathy and seizures with prolonged use.
| Breastfeeding | Tinidazole is excreted in human breast milk. The milk-to-plasma ratio is approximately 1.0. After a single 2 g dose, peak milk concentrations occur at 2-4 hours and can be as high as 10-20 mcg/mL. The relative infant dose is estimated to be about 20-25% of the maternal weight-adjusted dose. Breastfeeding should be avoided for 96 hours after a dose. |
| Teratogenic Risk | Tinidazole is classified as FDA Pregnancy Category C. Animal studies have shown embryotoxicity and fetotoxicity at doses similar to human therapeutic levels. There are no adequate and well-controlled studies in pregnant women. Use in the first trimester is generally avoided due to potential teratogenic risk. In the second and third trimesters, use only if clearly needed and if the benefit outweighs the potential risk to the fetus. |
■ FDA Black Box Warning
No FDA black box warning exists for tinidazole.
| Common Effects | giardiasis |
| Serious Effects |
["Hypersensitivity to tinidazole, other nitroimidazoles, or any component of the formulation","First trimester of pregnancy","Breastfeeding (during therapy and for 72 hours after dose)","History of blood dyscrasias (use with caution)"]
| Precautions | ["Carcinogenicity: Nitroimidazoles have been associated with increased tumor incidence in animal studies; avoid chronic use.","Neurological effects: Peripheral neuropathy and CNS effects (e.g., seizures, dizziness) may occur; discontinue if abnormal neurologic signs develop.","Blood dyscrasias: Leukopenia has been reported; monitor CBC with prolonged therapy.","Pregnancy: Use in first trimester is contraindicated; avoid in second and third trimesters unless necessary.","Lactation: Excreted in breast milk; avoid breastfeeding during therapy and for 72 hours after last dose."] |
Loading safety data…
| Fetal Monitoring | Monitor maternal liver function tests and renal function. Watch for signs of hypersensitivity, gastrointestinal distress, and neurological symptoms (dizziness, headache, seizures). No specific fetal monitoring is required, but ultrasound may be considered if there are concerns about fetal growth or development. |
| Fertility Effects | No specific studies on human fertility. Animal studies have not shown impaired fertility at therapeutic doses. Tinidazole may transiently affect sperm motility in vitro, but clinical significance is unknown. |