Amoxicillin-clavulanate is the first-line antibiotic for bacterial sinus infections in both adults and children. But most sinus infections are viral, meaning antibiotics won’t help at all. The antibiotic your doctor picks, and whether you need one in the first place, depends on how long you’ve been sick, how severe your symptoms are, and whether you have drug allergies.
Most Sinus Infections Don’t Need Antibiotics
The majority of sinus infections start with a virus, and viral infections clear up on their own. Antibiotics only work against bacteria. Three specific patterns suggest your sinus infection has become bacterial and may benefit from antibiotic treatment:
- Persistent symptoms: Congestion, facial pressure, and nasal discharge lasting 10 days or more with no improvement.
- Severe onset: A fever of 102°F (39°C) or higher with thick, discolored nasal discharge or facial pain lasting at least 3 to 4 days straight.
- Double sickening: You start to feel better after a typical cold, then around day 5 or 6, symptoms come back worse with new fever, increased discharge, or headache.
If your symptoms don’t fit one of these patterns, you likely have a viral infection. Decongestants, saline rinses, and pain relievers are the appropriate treatment while your body fights it off.
First-Line Antibiotic: Amoxicillin-Clavulanate
Amoxicillin-clavulanate (brand name Augmentin) is the go-to choice for acute bacterial sinusitis. It combines amoxicillin, a penicillin-type antibiotic, with clavulanate, an ingredient that helps it work against bacteria that have developed resistance to plain amoxicillin. Some guidelines still list plain amoxicillin as an acceptable first choice, but the combination version covers a wider range of the bacteria that commonly cause sinus infections, including strains that produce enzymes to break down basic penicillin.
Your doctor may prescribe a higher dose if you live in an area with significant antibiotic resistance, if you’ve used antibiotics recently, or if your infection is more severe. For children, dosing is based on weight, typically ranging from 45 to 90 mg per kilogram per day depending on severity.
Why the Z-Pak Is No Longer Recommended
Azithromycin (the familiar Z-Pak) was once widely prescribed for sinus infections, but guidelines now recommend against it. The reason is straightforward: the bacteria most commonly responsible for sinus infections have become highly resistant to it. A large study across 329 U.S. hospitals found that roughly 40% of Streptococcus pneumoniae samples were resistant to macrolide antibiotics like azithromycin. Among respiratory samples specifically, resistance climbed to 47%. These rates have been consistently high for years, with earlier studies showing azithromycin resistance approaching 48%.
Guidelines state that macrolide antibiotics should only be used when local resistance rates fall below 25%. Every U.S. region now exceeds that threshold for respiratory infections. If your doctor prescribes a Z-Pak for a sinus infection, it’s reasonable to ask about alternatives that are more likely to work.
Options If You’re Allergic to Penicillin
If you have a penicillin allergy, doxycycline is the preferred alternative for adults. It’s a tetracycline antibiotic taken by mouth, typically twice daily. Respiratory fluoroquinolones like levofloxacin or moxifloxacin are also effective, but they come with significant caveats (more on that below). The American Academy of Family Physicians lists both doxycycline and respiratory fluoroquinolones as acceptable first-line options for penicillin-allergic patients.
It’s worth noting that many people who believe they’re allergic to penicillin actually aren’t. If your allergy was diagnosed in childhood or based on a mild rash, allergy testing can sometimes clear you for penicillin-based antibiotics, which opens up more treatment options.
Fluoroquinolones: Effective but Restricted
Levofloxacin and moxifloxacin are powerful antibiotics that work well against sinus infections, but the FDA has placed strict limits on their use. These drugs carry risks of serious side effects including tendon damage, nerve damage, and joint problems that can be disabling and potentially permanent. The FDA’s position is clear: fluoroquinolones should be reserved for patients who have no other treatment options for acute bacterial sinusitis because the risks generally outweigh the benefits when safer alternatives exist.
If a fluoroquinolone is prescribed for your sinus infection and you haven’t tried amoxicillin-clavulanate or doxycycline first, ask your provider why those options were skipped.
How Long You Need to Take Them
Traditionally, guidelines called for 10 to 14 days of antibiotics for a sinus infection. Newer evidence suggests shorter courses work just as well. A meta-analysis of 12 randomized trials involving over 4,400 patients found no difference in cure rates between short courses (3 to 7 days) and longer courses (6 to 10 days). When researchers specifically compared 5-day versus 10-day regimens, cure rates were essentially identical, but patients on the shorter course experienced fewer side effects.
Most doctors now prescribe 5 to 7 days for uncomplicated acute bacterial sinusitis. Your provider may opt for a longer course if your symptoms are severe, if you have underlying health conditions, or if you’ve had repeated infections. Follow whatever duration you’re prescribed, even if you start feeling better before you finish.
Chronic Sinus Infections Need a Different Approach
Chronic sinusitis, defined as symptoms lasting 12 weeks or longer, involves different bacteria than acute infections. The usual culprits shift to include Staphylococcus aureus, anaerobic bacteria, and certain gram-negative organisms that aren’t typically involved in short-term infections. Because of this broader bacterial mix, plain amoxicillin isn’t enough. Amoxicillin-clavulanate or a fluoroquinolone like moxifloxacin is recommended for chronic cases, and treatment courses tend to run longer than those for acute infections.
Chronic sinusitis also frequently involves factors beyond infection alone, such as nasal polyps, allergies, or structural problems. Antibiotics may be only one part of the treatment plan, alongside nasal corticosteroid sprays, saline irrigation, or in some cases surgery.
Managing Side Effects
Amoxicillin-clavulanate commonly causes digestive issues. Diarrhea, nausea, and stomach discomfort are the most frequent complaints, driven largely by the clavulanate component. Taking the medication with food can reduce stomach upset. Eating probiotic-rich foods like yogurt during your course may help maintain healthy gut bacteria and reduce the risk of diarrhea.
Yeast infections are another common side effect of antibiotics, particularly in women. Antibiotics disrupt the normal balance of microorganisms in the body, allowing yeast to overgrow. Over-the-counter antifungal treatments are usually sufficient if this occurs.
Children and Sinus Infections
In children, the antibiotic decision depends on symptom severity. For severe or worsening symptoms, antibiotics are recommended right away, with amoxicillin or amoxicillin-clavulanate as first-line choices. For persistent symptoms (lasting more than 10 days without improvement), parents and doctors can choose between starting antibiotics immediately or watching for another 72 hours to see if the child improves on their own. If there’s no improvement after that observation window, antibiotics should be started.
Dosing for children is weight-based. Standard dosing runs 40 to 45 mg per kilogram per day, while high-dose regimens use 90 mg per kilogram per day for more resistant infections. Cefuroxime, a different type of antibiotic, is another option at 30 mg per kilogram per day for children who can’t tolerate amoxicillin-based drugs.
Signs the Infection Is Spreading
Bacterial sinus infections can, in rare cases, spread to nearby structures. Seek immediate medical care if you develop swelling or redness around the eyes, high fever, double vision or other vision changes, confusion, or a stiff neck. These symptoms can signal complications like orbital cellulitis (infection around the eye socket), meningitis, or bone infection. These are emergencies that require prompt treatment, not situations where you can wait for a scheduled appointment.