1. Clinical Overview
A fixed-dose combination (FDC) antifungal and antiprotozoal/antibacterial agent. Fluconazole is a triazole antifungal that inhibits fungal cytochrome P450 14α-demethylase, disrupting ergosterol synthesis in fungal cell membranes. Tinidazole is a nitroimidazole antimicrobial effective against anaerobic bacteria and protozoa by damaging their DNA. This combination is primarily used in gynecological infections where mixed fungal (Candida) and anaerobic/trichomonal infections are suspected or confirmed. Its use as an FDC is controversial and has been scrutinized by regulatory authorities due to potential for inappropriate use and increased antimicrobial resistance.
| Onset | Duration | Bioavailability |
|---|---|---|
| Fluconazole: Symptomatic relief often within 24-72 hours. Tinidazole: Rapid, with peak plasma concentrations within 2 hours. | Fluconazole: Long duration due to long half-life (approx. 30 hours), allowing for single-dose regimens in vulvovaginal candidiasis. Tinidazole: Plasma levels remain therapeutic for 24-72 hours depending on dose. | Fluconazole: >90% (oral). Tinidazole: ~100% (oral). |
2. Mechanism of Action
Fluconazole exerts its antifungal effect by selectively inhibiting the fungal cytochrome P450 enzyme lanosterol 14-α-demethylase. This inhibition blocks the conversion of lanosterol to ergosterol, an essential component of the fungal cell membrane, leading to increased membrane permeability and inhibition of fungal growth. Tinidazole, after entering the microbial cell, is reduced by nitroreductase enzymes in anaerobic bacteria and protozoa. This reduction generates reactive nitro radical anions that cause strand breaks in microbial DNA, inhibiting nucleic acid synthesis and leading to cell death.
3. Indications & Uses
- Mixed vaginal infections with documented or high suspicion of concurrent vulvovaginal candidiasis and trichomoniasis/bacterial vaginosis.
- Recurrent vaginal discharge where mixed etiology is confirmed.
4. Dosage & Administration
Adult Dosage: Commonly available as a single-dose therapy: Fluconazole 150 mg + Tinidazole 500 mg or 1000 mg, taken orally as a single dose. Some regimens may use Fluconazole 150 mg + Tinidazole 2 gm as a single dose. A 3-day course (once daily) is also marketed. MUST be taken with or after food.
Administration: Take orally with a full glass of water, during or immediately after a meal to minimize gastrointestinal upset. Do not crush or chew the tablet unless specified. Complete the full prescribed course even if symptoms improve.
5. Side Effects
Common side effects may include:
- Nausea
- Abdominal pain/discomfort
- Headache
- Diarrhea or constipation
- Dizziness
- Metallic/bitter taste in mouth (Tinidazole)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin | Fluconazole inhibits metabolism, increasing INR and bleeding risk. | Major |
| Sulfonylureas (e.g., Glipizide) | Fluconazole increases sulfonylurea levels, causing hypoglycemia. | Major |
| Phenytoin | Fluconazole increases phenytoin levels; phenytoin may decrease fluconazole levels. | Major |
| Rifampicin | Decreases Fluconazole levels significantly. | Major |
| Cyclosporine, Tacrolimus | Fluconazole increases calcineurin inhibitor levels, risking nephrotoxicity. | Major |
| Statins (Metabolized by CYP3A4 e.g., Atorvastatin) | Increased risk of myopathy/rhabdomyolysis. | Moderate |
| Oral Contraceptives | Potential for decreased efficacy; use backup method. | Moderate |
| Lithium | Tinidazole may increase lithium levels, causing toxicity. | Moderate |
| Disulfiram | Increased risk of psychotic reactions with Tinidazole. | Major |
| Alcohol & Alcohol-containing products | Disulfiram-like reaction with Tinidazole (flushing, nausea, vomiting, palpitations). | Major |
7. Patient Counselling
- DO take the medication with food.
- DO complete the full course as prescribed.
- DO inform your doctor about all other medications you are taking.
- DO use effective non-hormonal contraception if on oral contraceptives.
- DON'T consume any alcohol, including beer, wine, spirits, and food cooked with alcohol, for at least 3 days after your last dose.
- DON'T drive or operate heavy machinery if you feel dizzy.
- DON'T take it if you are pregnant or suspect pregnancy without consulting your doctor.
8. Toxicology & Storage
Overdose: Nausea, vomiting, diarrhea, abdominal pain. In severe cases: CNS effects (seizures, hallucinations, dizziness), hepatotoxicity, QT prolongation leading to arrhythmias.
Storage: Store below 30°C, in a cool, dry place. Protect from light and moisture. Keep out of reach of children.