Amoxicillin is the standard first-line antibiotic for a bacterial sinus infection. For mild to moderate cases, plain amoxicillin works well. For more severe symptoms, or if you’ve recently taken antibiotics, your doctor will likely prescribe amoxicillin-clavulanate, which adds a compound that helps the antibiotic work against resistant bacteria.
Most Sinus Infections Don’t Need Antibiotics
Before getting into which antibiotic works best, it’s worth knowing that the vast majority of sinus infections are viral, not bacterial. Antibiotics do nothing against viruses. Even among confirmed bacterial cases, 46% resolve on their own within a week and 64% clear up within two weeks without any antibiotic. When antibiotics are prescribed for bacterial sinusitis, they only improve the cure rate by about 6 percentage points. That means roughly 17 people need to take antibiotics for one additional person to benefit beyond what would have happened naturally.
This is why doctors are often reluctant to prescribe antibiotics right away. For most people with a sinus infection, the best initial approach is managing symptoms with decongestants, saline rinses, and pain relievers while waiting to see if things improve.
When a Sinus Infection Is Likely Bacterial
Your doctor will consider antibiotics when symptoms point toward a bacterial cause. The clinical criteria include a fever above 102°F, one-sided facial pain or pressure, and thick discolored discharge with nasal congestion lasting three or more days. Tooth pain and detecting a foul smell that isn’t coming from an outside source also raise the likelihood.
One common misconception: the color of your nasal discharge doesn’t reliably distinguish bacterial from viral infections. Green or yellow mucus can show up with either type. Your doctor’s overall clinical impression, weighing all your symptoms together, is actually the single most useful factor in telling the two apart.
First-Line Antibiotics
For uncomplicated bacterial sinusitis, amoxicillin is the go-to choice. It’s inexpensive, well-tolerated, and effective against the most common bacteria that cause sinus infections, particularly Streptococcus pneumoniae.
If your symptoms are severe, if you’ve used antibiotics in the past month, or if you haven’t improved after a few days on plain amoxicillin, amoxicillin-clavulanate is the next step. The added ingredient (clavulanate) blocks an enzyme that some bacteria produce to disable amoxicillin, making the drug effective against a wider range of bugs. A typical adult course for the extended-release version is taken every 12 hours for 10 days, though your doctor may adjust the duration. Children’s doses are weight-based.
Whichever antibiotic you’re prescribed, finishing the full course matters. Stopping early because you feel better can leave bacteria partially alive, increasing the chance of the infection returning or becoming resistant.
Options for Penicillin Allergies
If you’re allergic to penicillin, the alternatives depend on how severe your allergy is. For people with a mild or uncertain allergy history, certain cephalosporin antibiotics (a related but distinct drug class) are often safe and effective. For people with a more serious penicillin allergy, doctors may turn to doxycycline or clindamycin.
Macrolide antibiotics like azithromycin (the popular “Z-Pack”) and clarithromycin have historically been used as alternatives, but their effectiveness has dropped. Resistance among the pneumococcus bacteria that commonly cause sinus infections has climbed to over 35%, meaning more than one in three strains won’t respond to these drugs. Infectious disease guidelines now recommend against using azithromycin for sinus infections. If your doctor prescribes it anyway, it may be worth asking about alternatives, as efficacy rates for macrolides top out around 70-80% compared to higher rates for first-line options.
Why Fluoroquinolones Are a Last Resort
Levofloxacin and moxifloxacin are powerful antibiotics that work well against sinus bacteria, but the FDA has placed a boxed warning (the most serious type) on these drugs for sinusitis. The agency concluded that the risks generally outweigh the benefits for sinus infections when other treatment options exist. Side effects can involve tendons, muscles, joints, nerves, and the central nervous system, and some of these effects can be disabling or permanent. These drugs should only be considered when no other antibiotic is appropriate.
Nasal Steroid Sprays as a Helpful Add-On
Nasal corticosteroid sprays, the kind you can buy over the counter for allergies, can improve recovery when used alongside antibiotics. They reduce the swelling inside your nasal passages and sinuses, helping trapped mucus drain and relieving pressure. For recurrent sinus infections, combining a nasal steroid spray with antibiotics has been shown to work better than antibiotics alone. Even if you don’t end up on antibiotics, these sprays can help manage symptoms during a viral infection.
What to Expect During Treatment
Most people start feeling better within two to three days of starting an antibiotic, though it can take longer. If your symptoms haven’t improved after three to five days, contact your doctor. This could mean the bacteria causing your infection are resistant to the antibiotic you’re taking, or that the diagnosis needs to be reconsidered. Your doctor may switch you to a different antibiotic or order imaging to get a better look at what’s going on.
Common side effects of amoxicillin and amoxicillin-clavulanate include diarrhea, nausea, and stomach upset. The clavulanate component is usually the culprit for digestive issues. Taking the medication with food can help. If you develop a rash, difficulty breathing, or significant swelling, stop the medication and seek medical attention, as these could signal an allergic reaction.