The top recommended antibiotic for a bacterial sinus infection is amoxicillin-clavulanate, a combination of amoxicillin plus a compound that helps it work against resistant bacteria. Most adults take it for five to seven days. But here’s the important caveat: the majority of sinus infections are viral, meaning antibiotics won’t help at all. Only when specific signs point to a bacterial cause do antibiotics become the right call.
When a Sinus Infection Actually Needs Antibiotics
Most sinus infections start with a cold virus, and your body clears them on its own within seven to ten days. Antibiotics only make sense when the infection is bacterial, and there are three patterns that signal a bacterial cause:
- Persistent symptoms: Congestion, facial pressure, and nasal discharge that last 10 days or longer without any improvement.
- Severe onset: A fever of 102°F or higher alongside thick nasal discharge and facial pain lasting three to four consecutive days.
- Double worsening: Symptoms that seem to improve after four to seven days, then suddenly get worse again.
If your symptoms don’t match any of these patterns, you’re almost certainly dealing with a viral infection. Decongestants, saline rinses, and pain relievers will do more for you than any antibiotic.
The First-Choice Antibiotic
Amoxicillin-clavulanate (sometimes called by the brand name Augmentin) is preferred over plain amoxicillin for bacterial sinus infections in adults. The clavulanate component blocks an enzyme that certain bacteria produce to defend themselves against amoxicillin, making the combination effective against a wider range of bugs. A standard course runs five to seven days for adults.
Your doctor may prescribe a higher dose if you fall into certain risk categories: if you’ve taken antibiotics within the past month, if you live in an area with high rates of drug-resistant bacteria, if you’re over 65, if you were recently hospitalized, or if your immune system is compromised. These situations raise the odds that ordinary doses won’t be strong enough to clear the infection.
The most common downside of amoxicillin-clavulanate is digestive upset. Diarrhea is the side effect people notice most, and it can sometimes persist or appear even after you finish the course. Taking the medication with food helps reduce nausea and stomach discomfort. If you develop severe or bloody diarrhea, that warrants a call to your doctor right away.
Alternatives if You’re Allergic to Penicillin
Since amoxicillin-clavulanate is a penicillin-type drug, it’s off the table if you have a penicillin allergy. The two main alternatives for adults are doxycycline and respiratory fluoroquinolones (levofloxacin or moxifloxacin). Doxycycline is generally tried first because it’s effective against the bacteria that cause most sinus infections and carries fewer serious risks.
Fluoroquinolones are powerful, but the FDA has warned that their serious side effects, including tendon damage, nerve problems, and mood changes, generally outweigh the benefits for sinus infections when other options exist. They should be reserved for people who truly have no alternative. If your doctor prescribes one, it typically means other antibiotics have already failed or aren’t safe for you.
Why a Z-Pack Often Isn’t the Best Choice
Azithromycin (the “Z-pack”) is one of the most commonly requested antibiotics for sinus infections, but guidelines specifically recommend against it. The reason is resistance. One of the primary bacteria behind sinus infections has developed significant defenses against azithromycin and related drugs. In the United States, resistance rates in respiratory samples from adults have reached as high as 47%, meaning the antibiotic fails against nearly half of these infections. Guidelines from the Infectious Diseases Society of America explicitly state that azithromycin and a related drug, clarithromycin, should not be used as first-line treatment for bacterial sinusitis. The same goes for trimethoprim-sulfamethoxazole, another older antibiotic with high resistance rates.
If you’ve been prescribed a Z-pack for a sinus infection in the past and it seemed to work, there’s a good chance the infection was viral and would have resolved on its own regardless of the antibiotic.
What Happens When the First Antibiotic Doesn’t Work
If your symptoms haven’t improved after three to five days on amoxicillin-clavulanate, your doctor will typically switch to a different class of antibiotic. For adults, this usually means a higher dose of amoxicillin-clavulanate if you started on a standard dose, or a move to doxycycline or a fluoroquinolone. The goal is to cover bacteria that may be resistant to the first drug.
Repeated sinus infections that don’t respond to antibiotics, or symptoms lasting 12 weeks or more, suggest chronic sinusitis. That’s a different condition with different causes, sometimes involving structural issues in the sinuses, nasal polyps, or fungal infections, and it often requires evaluation by an ear, nose, and throat specialist rather than another round of antibiotics.
Antibiotics for Children With Sinus Infections
For kids, amoxicillin or amoxicillin-clavulanate remains the first choice, just as in adults. However, doctors may take a “watchful waiting” approach for up to three days in children whose symptoms are persistent but not severe, since many of these infections resolve without medication. If a child is vomiting and can’t keep oral medication down, a single injection of a different antibiotic can bridge the gap until they’re able to switch to a pill or liquid form.
Children with penicillin allergies have fewer options than adults. Doxycycline is generally avoided in young children, so alternatives typically include levofloxacin or a combination of clindamycin with a different type of antibiotic. Your pediatrician will choose based on your child’s age and the severity of the infection.
How to Get the Most From Your Course
Finishing the full course of antibiotics matters, even if you start feeling better after two or three days. Stopping early gives surviving bacteria a chance to rebound, potentially making the infection harder to treat the second time around. For most adults, that means committing to the full five to seven days.
While you’re on antibiotics, saline nasal rinses can help flush out mucus and speed up symptom relief. Over-the-counter pain relievers handle the facial pressure and headache that often linger even after the bacteria are under control. Decongestant sprays can open your nasal passages, but limit them to three days to avoid rebound congestion that makes things worse.