Metronidazole vs. Zithromax
See how Metronidazole and Zithromax compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Metronidazole treats parasitic and anaerobic bacterial infections like trichomoniasis and bacterial vaginosis, while Zithromax targets respiratory, skin, and certain sexually transmitted infections.
Metronidazole is usually taken multiple times a day for up to 7 to 10 days, while Zithromax often works with a short course or even a single dose thanks to its long tissue half-life.
Metronidazole carries a boxed warning for cancer seen in animal studies and reacts badly with alcohol, while Zithromax carries warnings for heart rhythm changes and liver injury.
Metronidazole vs. Zithromax Drug Summary
Metronidazole
Metronidazole is a nitroimidazole antimicrobial used to treat trichomoniasis, bacterial vaginosis, amebiasis, and anaerobic bacterial infections. It comes as an oral tablet or capsule, and is also available as an IV, topical gel, or vaginal gel, typically taken multiple times a day for several days.
Zithromax
Zithromax (azithromycin) is a macrolide antibacterial used to treat respiratory infections, skin infections, and certain sexually transmitted infections. It comes as an oral tablet or suspension, and its long tissue half-life allows short-course or even single-dose regimens.
Metronidazole vs. Zithromax Side Effects
Metronidazole
Zithromax
Metronidazole vs. Zithromax Dosage
Metronidazole
Zithromax
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg three times daily | Days 1-7 |
| Maximum dose | 500-750 mg three times daily | If needed |
| Dose changes | 2 increases | As tolerated |
| STAGE | DOSE | WHEN |
| Starting dose | 500 mg once daily | Day 1 |
| Maximum dose | 30 mg/kg single dose | If needed |
| Dose changes | 5 increases | As tolerated |
Metronidazole
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg three times daily | Days 1-7 |
| Maximum dose | 500-750 mg three times daily | If needed |
| Dose changes | 2 increases | As tolerated |
Zithromax
| STAGE | DOSE | WHEN |
| Starting dose | 500 mg once daily | Day 1 |
| Maximum dose | 30 mg/kg single dose | If needed |
| Dose changes | 5 increases | As tolerated |
Metronidazole vs. Zithromax Indications
Metronidazole
Metronidazole is a first-line treatment for trichomoniasis and bacterial vaginosis, and is also used for amebiasis and serious anaerobic bacterial infections like intra-abdominal abscesses. It is sometimes used off-label as part of combination therapy for H. pylori or C. difficile infection.
Trichomoniasis (symptomatic and asymptomatic)
Bacterial vaginosis
Amebiasis
Intra-abdominal infections (peritonitis, abscess)
H. pylori and C. difficile (off-label)
Zithromax
Zithromax treats common respiratory infections like pneumonia, bronchitis, and sinusitis, as well as skin infections and certain sexually transmitted infections. It is also used to prevent and treat disseminated MAC disease in patients with weakened immune systems.
Community-acquired pneumonia
Acute bacterial sinusitis and bronchitis
Skin and skin structure infections
Chlamydia and gonorrhea urethritis/cervicitis
Traveler's diarrhea (off-label)
Metronidazole vs. Zithromax Pros and Cons
Metronidazole
Metronidazole has decades of clinical use as a first-line agent for trichomoniasis and bacterial vaginosis, with a well-established safety profile at the cost of a multi-day dosing schedule. It is one of the most affordable generic antibiotics and comes in oral, IV, topical, and vaginal forms.
Pros
First-line treatment for trichomoniasis and bacterial vaginosis
Roughly $15 to $40 per month, one of the cheapest generic antibiotics
Available in oral, IV, topical, and vaginal forms
Cons
Boxed warning for carcinogenicity seen in animal studies
Causes a disulfiram-like reaction with alcohol
Usually requires dosing multiple times a day for up to 10 days
Risk of seizures and peripheral neuropathy with prolonged use
Zithromax
Zithromax's long tissue half-life allows short courses or single-dose regimens that are easier to complete than multi-day antibiotics. It covers a broader range of respiratory and sexually transmitted infections but costs more and carries cardiac warnings.
Pros
Short-course or single-dose regimens improve treatment adherence
Covers a broad range of respiratory and skin infections
Approved for chlamydia, gonorrhea, and MAC prevention/treatment
Cons
Roughly $45 to $150 per treatment course, more than metronidazole
Risk of QT prolongation and dangerous heart arrhythmias
Rare but serious, sometimes fatal, liver injury
Can worsen symptoms of myasthenia gravis
Common Symptoms and Related Diseases You Can Explore
Explore a range of common symptoms the Doctronic Symptom Checker can help you understand.