Amoxicillin-clavulanate (brand name Augmentin) is the top recommended antibiotic for bacterial sinus infections in both adults and children. But here’s the critical detail most people searching this question need to hear first: the vast majority of sinus infections are caused by viruses, not bacteria, and antibiotics won’t help a viral infection at all. Knowing when you actually need an antibiotic matters just as much as knowing which one to take.
Most Sinus Infections Don’t Need Antibiotics
A typical sinus infection starts with a cold virus. Your sinuses get inflamed, mucus builds up, and you feel miserable with facial pressure, congestion, and thick nasal discharge. This is viral sinusitis, and it resolves on its own within 7 to 10 days. Antibiotics do nothing against viruses.
A bacterial sinus infection is suspected when symptoms last longer than 10 days without improving, when symptoms start to get better and then suddenly worsen again (sometimes called “double worsening”), or when symptoms are unusually severe from the start, with a high fever above 102°F (39°C) and thick, colored nasal discharge lasting at least 3 to 4 consecutive days. If your sinus infection doesn’t fit any of these patterns, you’re almost certainly dealing with a virus.
First-Line Antibiotic: Amoxicillin-Clavulanate
When a bacterial sinus infection is confirmed or strongly suspected, the standard first choice is amoxicillin-clavulanate. For adults, the typical dose is 875 mg/125 mg taken twice daily. The clavulanate component helps the amoxicillin work against bacteria that would otherwise resist it, which is why plain amoxicillin alone is no longer the go-to for adults in most guidelines.
Treatment courses are shorter than many people expect. Current guidelines from the Infectious Diseases Society of America recommend 5 to 7 days of antibiotic therapy for uncomplicated cases. The old standard of 10 to 14 days is no longer necessary for most adults with straightforward infections. Most patients see both symptom relief and bacterial clearance within 72 hours of starting treatment. If you don’t feel noticeably better within 48 to 72 hours, the bacteria causing your infection may be resistant to the antibiotic, and your doctor will likely switch you to a different one.
Antibiotics for Children
For kids under 18, the approach is slightly different. High-dose amoxicillin is the first-line treatment, dosed by body weight at 80 to 90 mg per kilogram per day, split into two doses. This higher dose is used because a significant percentage of the most common sinus bacteria in children have reduced susceptibility to standard-dose amoxicillin.
If a child has taken amoxicillin in the past month or doesn’t improve on it, the step up is amoxicillin-clavulanate at the same high-dose range. The same 5 to 7 day course applies for uncomplicated cases, though your pediatrician may extend treatment if severe symptoms persist beyond 5 days.
Options If You’re Allergic to Penicillin
Since amoxicillin-clavulanate is a penicillin-based drug, it’s off the table if you have a penicillin allergy. The recommended alternative is doxycycline, taken as 100 mg twice daily or 200 mg once daily. It covers the same bacteria effectively and is well tolerated by most adults, though it’s not typically used in young children.
If your allergy is mild enough that you can still tolerate cephalosporins (a related but distinct class of antibiotics), third-generation cephalosporins like cefixime or cefpodoxime are another option. These are sometimes combined with clindamycin for broader coverage. Your doctor can help determine whether your specific allergy makes cephalosporins safe for you, since true cross-reactivity between penicillins and cephalosporins is relatively uncommon.
Why Azithromycin Is No Longer Recommended
If you’ve been prescribed a Z-Pack (azithromycin) for a sinus infection in the past, you’re not alone. It used to be widely prescribed because it’s convenient: just 5 days, once daily, and easy on the stomach. The problem is that the bacteria most commonly responsible for sinus infections have developed extensive resistance to azithromycin and the entire macrolide class of antibiotics. Resistance rates among the key sinus bacteria are extremely high, with multidrug-resistant strains now approaching 60% prevalence in many regions. Prescribing azithromycin for sinusitis today means a significant chance the antibiotic simply won’t work.
When Stronger Antibiotics Are Considered
Respiratory fluoroquinolones like levofloxacin and moxifloxacin are powerful antibiotics that do work against sinus infections, but they carry serious enough risks that they’re reserved for situations where safer options have failed or can’t be used. The FDA has issued strong warnings about these drugs because they can cause tendon inflammation and rupture (especially in people over 60), nerve damage that may be permanent, and neurological side effects affecting the brain and nervous system. These side effects can appear after just one dose.
For a straightforward sinus infection, the risks of fluoroquinolones outweigh their benefits. They’re appropriate when you’ve already failed a course of first-line antibiotics, when you have a complicated infection involving spread beyond the sinuses, or when allergies rule out every safer alternative. If your doctor prescribes one, it’s worth asking whether any other options remain.
What to Expect During Treatment
Once you start the right antibiotic, improvement typically comes fast. Most people notice their symptoms easing within 72 hours. Facial pressure decreases, fever breaks, and nasal discharge starts to thin out and clear up. You should finish the full prescribed course even after you feel better, since stopping early can allow surviving bacteria to regrow and potentially develop resistance.
If your symptoms haven’t budged after 3 days on an antibiotic, contact your doctor. This usually means the bacteria are resistant to that particular drug, and switching to a different antibiotic class will be necessary. Rarely, persistent symptoms can signal a complication like an abscess or spread of infection that needs more aggressive treatment.
While waiting for antibiotics to work, or if your infection turns out to be viral, saline nasal rinses, steam inhalation, and over-the-counter pain relievers can help manage symptoms. Nasal corticosteroid sprays also reduce inflammation and may speed recovery regardless of whether the infection is bacterial or viral.