What to expect when taking amoxicillin for a sinus infection

In this article:

• Amoxicillin for sinus infection
• How long does it take to work?
• Dosage
• Why isn’t it working?
• Considerations
• Your personalized path to relief

In this article

• Amoxicillin for sinus infection
• How long does it take to work?
• Dosage
• Why isn’t it working?
• Considerations
• Your personalized path to relief

Amoxicillin is one of the most commonly prescribed antibiotics in the U.S. and is part of the penicillin family of medications. Healthcare providers use it to treat a wide range of bacterial infections, including those affecting the ear, skin, and urinary tract. If you’ve been prescribed amoxicillin for a sinus infection, here’s what to know about how it works, when it can help, and what to expect during treatment.

Is amoxicillin good for a sinus infection?

“For those without a penicillin allergy, amoxicillin for five to seven days is an appropriate choice for a first-line antibiotic,” says Jennifer Villwock, MD, Vice Chair of Research at the University Hospitals Ear, Nose & Throat Institute in Ohio.

Your sinuses are hollow cavities in the skull that can become inflamed and congested due to viruses, bacteria, allergies, or other irritants. When swelling blocks normal drainage, mucus can build up and, in some cases, lead to a secondary bacterial infection.

Many cases of acute sinusitis improve on their own within seven to 10 days, and self-care measures can help relieve symptoms. When a bacterial infection is suspected, however, antibiotics may be necessary. Amoxicillin, a beta-lactam antibiotic, is commonly prescribed and often considered a first-line option.

In some cases, providers may prescribe a different antibiotic, such as Zithromax (azithromycin), which belongs to the macrolide class of antibiotics. However, research suggests that macrolides may be less effective as an initial treatment for acute bacterial rhinosinusitis due to the rising resistance of Streptococcus pneumoniae bacteria.

Importantly, antibiotics aren’t needed for every sinus infection. According to the Centers for Disease Control and Prevention (CDC), only bacterial sinus infections are typically treated with antibiotics. Most cases are caused by viruses, which antibiotics can’t treat. In fact, one study of children found that those with nasopharyngeal bacterial colonization are significantly more likely to benefit from antibiotics than those without colonization.

Uma Darji, MD, a family medicine provider in North Carolina, helps her patients understand that antibiotics won’t speed recovery when a sinus infection is viral. “I focus on what will help right away, such as saline rinses, hydration, and over-the-counter medications,” says Dr. Darji. “Also, I have found it is key to remind them that if things aren’t improving, we can always reassess.”

How long does it take amoxicillin to work for a sinus infection?

Most people begin to feel better after taking about five doses of amoxicillin, which corresponds to about two or three days.

“But I always remind patients to please finish the entire course and to contact me if they aren’t getting better or if they are getting worse after a few days,” Dr. Darji adds. Completing the full prescription reduces antibiotic resistance.

Amoxicillin dosage for sinus infection

Amoxicillin is available in several oral forms, including capsules, tablets, chewables, and liquid suspension. Depending on the prescription, it’s typically taken every eight or 12 hours.

For bacterial sinus infections, a provider may prescribe amoxicillin alone or combine it with clavulanate (commonly sold as Augmentin) for more persistent or severe cases.

“When I prescribe amoxicillin or amoxicillin-clavulanate, it’s usually Augmentin twice a day for five to seven days, ten in some serious cases,” Dr. Darji says.

For adults and children weighing 40 kg (about 88 pounds) or more, typical dosing ranges from 250 to 500 mg every eight hours or 500 to 875 mg every 12 hours. Treatment guidance for sinus infections varies for children and adults.

Healthcare providers usually stress the importance of completing the prescribed course of antibiotics, even if symptoms improve sooner. While some research suggests shorter courses may be effective for certain people, you should only adjust or stop an antibiotic under the guidance of your healthcare provider.

Why don’t all bacterial infections respond?

Even when a sinus infection is bacterial, amoxicillin doesn’t always work. One common reason is antibiotic resistance, which occurs when bacteria adapt and survive despite antibiotic treatment.

If an antibiotic doesn’t eliminate all the bacteria (such as when it’s stopped too soon, or the bacteria are already resistant), the remaining bacteria can multiply and become harder to treat. Antibiotic resistance can limit treatment options, delay recovery, and increase the risk of more severe infections that require stronger medications with greater side effects.

If your symptoms don’t improve or worsen after a few days of taking amoxicillin, contact your healthcare provider. They may recommend a different antibiotic, additional testing, or another treatment approach.

Important considerations and red flags

Like all medications, amoxicillin can cause side effects. The most common are gastrointestinal issues such as nausea, vomiting, diarrhea, and an upset stomach. Some people may also experience dizziness or lightheadedness.

Dr. Villwock notes that most of the time, side effects are mild. However, she cautions, “They can also be serious, such as C. difficile infection, as this bad bacteria overgrows in the gut because the antibiotic is killing the good bacteria there.”

Allergies are another critical consideration. Because amoxicillin is a penicillin antibiotic, it should not be taken by anyone with a known penicillin allergy or a history of allergic reactions to penicillin. Symptoms of an allergic reaction can include hives, itching, swelling of the face or tongue, fever, and shortness of breath. In such cases, an alternative antibiotic may be more suitable, such as doxycycline, certain cephalosporins like Suprax (cefixime), or fluoroquinolones like moxifloxacin or levofloxacin.

Antibiotics can also disrupt the body’s natural balance of bacteria, sometimes increasing the risk of yeast infections. Some people find that probiotic supplements or foods like yogurt help support gut health during treatment.

Your personalized path to relief

The best treatment is prevention. To reduce the chances of getting sick, prioritize healthy habits, such as handwashing and avoiding contact with contaminated surfaces. “If traveling or around lots of people, wearing a mask can also be helpful to reduce the risk of infections,” Dr. Villwock suggests. 

Despite these measures, you may still get sick sometimes. “Upper respiratory tract infections and sinus infections are an unfortunate fact of life,” Dr. Villwock notes.

Your primary care provider can help you determine a personalized plan of care for your sinus infection. You may or may not need antibiotic therapy for a case of acute sinusitis. Additionally, taking antibiotics like amoxicillin isn’t the only way to find relief from the symptoms of a sinus infection. These at-home remedies can help:

• Rinse your sinuses with a warm saline solution
• Use a topical nasal spray, such as a nasal corticosteroid spray to relieve stuffy nose
• Take a decongestant to shrink the swollen tissues in the nasal cavity and reduce nasal congestion
• Take a mucolytic medication, such as Mucinex (guaifenesin), to thin the mucus in your sinuses.
• Breathe in warm, moist air

Over-the-counter pain relievers, such as acetaminophen or ibuprofen, may help reduce facial pain and pressure-related sinus pain. 

If you have allergies that may be contributing to or exacerbating a sinus infection, talk to your provider about the most appropriate use of allergy treatments. Additionally, if you have a persistent sinus infection that doesn’t seem to be improving, consult a healthcare professional. Some acute cases can develop into chronic sinusitis and may exhibit more severe symptoms that require additional treatment.