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. |
| Molecular Weight | 247.14 |
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 | Contraindicated due to potential teratogenicity (nitroimidazole class). Avoid use in first trimester unless no alternative. |
| 2nd trimester | Use only if clearly needed; animal data show risk, but human data limited. Avoid if possible. |
| 3rd trimester | Use only if clearly needed; may be used for trichomoniasis after first trimester. Monitor for neonatal effects if used near term. |
Clinical note
Disulfiram-like reaction can occur with alcohol Can cause peripheral neuropathy and seizures with prolonged use.
| Placental transfer | Crosses the placenta readily with fetal concentrations similar to maternal levels. |
| Breastfeeding | Excreted into breast milk in significant amounts. The manufacturer recommends discontinuing breastfeeding during therapy and for 72 hours after last dose due to potential adverse effects in nursing infants. |
■ FDA Black Box Warning
No FDA black box warning exists for tinidazole.
| Common Effects | giardiasis |
| Serious Effects |
Hypersensitivity to tinidazole or other nitroimidazole derivativesFirst trimester of pregnancy (unless no alternative)Breastfeeding (during therapy and for 72 hours after last dose)Blood dyscrasias or active neurological disorders (relative, but may be considered absolute in some settings)
| 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…
| Lactation Rating | L4 (Possibly Hazardous) |
| 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. |
| 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. |
| Food/Dietary | Avoid alcohol and alcohol-containing foods (e.g., sauces, vinegars, mouthwash) during therapy and for 72 hours post-therapy due to disulfiram-like reaction. Food does not significantly affect absorption but may reduce GI side effects. |
| Clinical Pearls | Tinidazole has a longer half-life (12-14h) than metronidazole, allowing once-daily dosing. It achieves high tissue penetration including CSF. Avoid alcohol during therapy and for 72 hours after last dose due to disulfiram-like reaction. Use with caution in patients with CNS disorders due to risk of seizures and peripheral neuropathy. Monitor INR in patients on warfarin as tinidazole potentiates anticoagulant effect. |
| Patient Advice | Take with food to reduce GI upset. · Do not drink alcohol or use alcohol-containing products during treatment and for 3 days after finishing. · Complete full course even if feeling better. · Report symptoms of neuropathy like numbness or tingling. · May cause metallic taste; this is temporary. |