Amoxicillin Dosage for Sinus Infection: The Evidence-Based Protocol Most Doctors Follow

Reviewed by FormBlends Medical Team · Last updated September 5, 2026 · 11 sources cited

Key Takeaways

• The FDA amoxicillin label lists 500 mg every 12 hours or 250 mg every 8 hours for mild to moderate ear, nose and throat infections, and 875 mg every 12 hours or 500 mg every 8 hours for severe infections; the AAO-HNS 2015 adult guideline uses a 5 to 10 day course
• The IDSA 2012 guideline recommends amoxicillin-clavulanate rather than amoxicillin alone as empiric first-line therapy, and reserves a high-dose regimen (2 g twice daily in adults, 90 mg/kg/day in children) for patients with resistance risk factors such as antibiotic use in the past month
• Most sinus infections are viral and resolve without antibiotics, making the 7-to-10-day symptom rule the key decision point for starting treatment
• Amoxicillin-clavulanate (Augmentin) replaces plain amoxicillin when beta-lactamase-producing bacteria are likely, but comes with higher gastrointestinal side effects

The short answer

As of September 5, 2026, the FDA amoxicillin label lists 500 mg every 12 hours or 250 mg every 8 hours for mild to moderate ear, nose and throat infections in adults, and 875 mg every 12 hours or 500 mg every 8 hours for severe infections. The AAO-HNS 2015 adult guideline allows amoxicillin with or without clavulanate for 5 to 10 days, while the IDSA 2012 guideline prefers amoxicillin-clavulanate as first-line. For children over 3 months the label gives 25 mg/kg/day (mild to moderate) or 45 mg/kg/day (severe) divided every 12 hours; the AAP 2013 guideline uses 45 mg/kg/day, or 80 to 90 mg/kg/day where resistance is common.

Table of contents

1. When antibiotics are actually indicated for sinus infections
2. Standard-dose amoxicillin protocol (500 mg three times daily)
3. High-dose amoxicillin protocol (875 to 1000 mg twice daily)
4. Pediatric dosing by weight and age
5. What most articles get wrong about treatment duration
6. When to switch from amoxicillin to amoxicillin-clavulanate
7. The resistance decision tree: which dose for which patient
8. Common dosing errors and how to avoid them
9. Storage, missed doses, and early discontinuation warnings
10. When to call your provider about treatment failure
11. Correction and guideline check, September 2026
12. FAQ
13. Sources

When antibiotics are actually indicated for sinus infections

Most acute rhinosinusitis is viral. The AAO-HNS 2015 adult guideline notes that only about 0.5 to 2% of viral upper respiratory infections progress to bacterial sinusitis (Rosenfeld et al., Otolaryngology - Head and Neck Surgery 2015). Bacterial sinusitis is a clinical diagnosis based on symptom duration and severity, not imaging or culture.

The 2012 Infectious Diseases Society of America (IDSA) guidelines define three patterns that justify antibiotic treatment:

Pattern 1: Persistent symptoms without improvement. Nasal discharge, congestion, or facial pain lasting 10 days or more without any sign of improvement.

Pattern 2: Severe symptoms. High fever (102°F or higher), purulent nasal discharge, and facial pain lasting at least 3 to 4 consecutive days at the start of illness.

Pattern 3: Worsening symptoms (double-sickening). Initial viral upper respiratory symptoms improve, then worsen after 5 to 6 days with new fever, headache, or increased nasal discharge.

If none of these patterns apply, watchful waiting is the evidence-based approach. The current Cochrane review (Lemiengre et al., 2018; 15 trials, 3,057 participants) found that without antibiotics 46% of patients were cured at one week and 64% at 14 days. Antibiotics cured about 5 to 11 more people per 100 (number needed to treat 19 for a clinical diagnosis), while 13 more per 100 had side effects (number needed to harm 8).

The pattern most providers see: patients presenting on day 3 or 4 of cold symptoms expecting antibiotics. The correct clinical response is to explain the 7-to-10-day rule and schedule a follow-up or callback if symptoms persist past day 10.

Standard-dose amoxicillin protocol (500 mg three times daily)

Correction, September 2026: an earlier version of this page attributed a plain amoxicillin 500 mg every 8 hours regimen to the IDSA guideline. IDSA 2012 in fact recommends amoxicillin-clavulanate rather than amoxicillin alone as empiric first-line therapy for adults and children (Chow et al., Clinical Infectious Diseases 2012). Plain amoxicillin is still an option under the AAO-HNS 2015 adult guideline, which allows amoxicillin with or without clavulanate for 5 to 10 days. The FDA label lists 500 mg every 8 hours as a severe-infection regimen and 500 mg every 12 hours for mild to moderate ear, nose and throat infections.

This dose achieves adequate serum and sinus tissue concentrations to cover penicillin-susceptible Streptococcus pneumoniae and Haemophilus influenzae, the two most common bacterial pathogens in community-acquired sinusitis.

Dosing schedule:

• 500 mg at 8:00 AM
• 500 mg at 4:00 PM
• 500 mg at midnight (or before bed)

The every-8-hour interval matters. Amoxicillin's half-life is 1 to 1.5 hours, and time above the minimum inhibitory concentration (MIC) is the pharmacodynamic parameter that predicts bacterial kill for beta-lactam antibiotics. Spacing doses evenly maintains therapeutic levels.

When standard-dose is appropriate:

• No antibiotic use in the past 3 months
• No recent hospitalization
• No immunocompromising conditions
• Low local pneumococcal resistance rates (less than 10% high-level resistance in your region)

A meta-analysis of 12 randomized trials (4,430 patients) found no difference in clinical success between short courses of 3 to 7 days and long courses of 6 to 10 days, with fewer adverse events in the 5-day arms of the five trials that compared 5 versus 10 days (Falagas et al., British Journal of Clinical Pharmacology 2009). The 2012 IDSA guidelines recommend 5 to 7 days for adults.

High-dose amoxicillin protocol (875 to 1000 mg twice daily)

Correction, September 2026: an earlier version of this page said IDSA 2012 made 875 or 1000 mg amoxicillin twice daily the preferred first-line regimen. It did not. The IDSA high-dose regimen is amoxicillin-clavulanate 2 g/125 mg orally twice daily in adults (90 mg/kg/day twice daily in children), recommended for regions with 10% or more penicillin-nonsusceptible S. pneumoniae, severe infection, daycare attendance, age under 2 or over 65, recent hospitalization, antibiotic use within the past month, or immunocompromise (Chow et al., Clinical Infectious Diseases 2012). The 875 mg every 12 hours figure is the FDA label's severe-infection dose for plain amoxicillin.

The label footnote is the relevant rule here: dosing for infections caused by organisms of intermediate susceptibility to amoxicillin should follow the recommendations for severe infections, which means 875 mg every 12 hours or 500 mg every 8 hours in adults.

Dosing schedule:

• 875 mg every 12 hours (e.g., 8:00 AM and 8:00 PM)
• Alternative: 500 mg every 8 hours (the label's other severe-infection regimen)

When IDSA 2012 calls for the high-dose amoxicillin-clavulanate regimen:

• Antibiotic use within the past month
• Daycare attendance or recent hospitalization
• Age under 2 or over 65
• Immunocompromise
• Regions where 10% or more of S. pneumoniae is penicillin-nonsusceptible
• Severe infection

The 875 mg formulation is dispensed as a single tablet taken twice daily, which many patients find easier to keep up with than a three-times-daily schedule. An earlier version of this page cited a 23% adherence improvement from a 2014 study; that figure could not be traced to any published source and has been removed.

Pediatric dosing by weight and age

Amoxicillin dosing in children is weight-based and divided into standard-dose and high-dose protocols, mirroring adult guidelines.

Weight (kg)	Weight (lb)	AAP 2013 standard dose (45 mg/kg/day)	AAP 2013 high dose (90 mg/kg/day)
10 kg	22 lb	225 mg twice daily	450 mg twice daily
15 kg	33 lb	337.5 mg twice daily	675 mg twice daily
20 kg	44 lb	450 mg twice daily	900 mg twice daily
25 kg	55 lb	562.5 mg twice daily	1125 mg twice daily
30 kg	66 lb	675 mg twice daily	1350 mg twice daily

Dosing notes:

• FDA label, mild to moderate ear, nose and throat infections in children over 3 months: 25 mg/kg/day divided every 12 hours, or 20 mg/kg/day divided every 8 hours
• FDA label, severe infections: 45 mg/kg/day divided every 12 hours, or 40 mg/kg/day divided every 8 hours; children weighing 40 kg or more are dosed as adults
• AAP 2013 guideline: 45 mg/kg/day standard, or 80 to 90 mg/kg/day divided every 12 hours where more than 10% of pneumococcus is penicillin-nonsusceptible or other risk factors apply, with a maximum of 2 g per dose
• IDSA 2012 recommends 10 to 14 days of treatment in children

Amoxicillin suspension is available in 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, and 400 mg/5 mL concentrations. The pharmacy calculates the milliliter volume per dose based on the child's weight and the prescribed mg/kg/day dose.

The American Academy of Pediatrics 2013 guideline recommends amoxicillin with or without clavulanate as first-line therapy for children with acute bacterial sinusitis, at 45 mg/kg/day as the standard dose, rising to 80 to 90 mg/kg/day (maximum 2 g per dose) in communities where more than 10% of pneumococcus is penicillin-nonsusceptible or when other risk factors are present, with reassessment at 72 hours (Wald et al., Pediatrics 2013). It does not recommend high-dose therapy for all children.

Common pediatric dosing error: parents confusing the concentration on the bottle. A child prescribed 450 mg receives 11.25 mL of the 400 mg/5 mL suspension, but only 9 mL of the 250 mg/5 mL suspension. Always use the dosing syringe or cup that comes with the prescription, and confirm the milliliter volume with the pharmacist.

What most articles get wrong about treatment duration

Most patient-facing articles cite "10 to 14 days" as the standard treatment duration for sinus infections. This is outdated.

The 2012 IDSA guidelines recommend 5 to 7 days of treatment for uncomplicated acute bacterial sinusitis in adults, and 10 to 14 days in children (Chow et al., Clinical Infectious Diseases 2012). The AAO-HNS 2015 adult guideline allows 5 to 10 days. So the old 10 to 14 day default is outdated for adults but remains the IDSA recommendation for children.

The Falagas 2009 meta-analysis described above (12 randomized trials, 4,430 patients) is the main evidence: short courses of 3 to 7 days matched long courses of 6 to 10 days for clinical success, and the 5-day arms had fewer adverse events than the 10-day arms. An earlier version of this page gave a 39% reduction in diarrhea; that figure is not in the paper and has been removed.

When longer treatment (10 to 14 days) is appropriate:

• Frontal or sphenoid sinusitis (deeper sinus involvement)
• Immunocompromised patients
• Severe infection with orbital or intracranial complications
• Lack of improvement after 5 to 7 days of treatment

The clinical decision point is symptom improvement by day 3 to 5. If the patient is improving, complete the 5-to-7-day course. If symptoms are unchanged or worsening, reassess for treatment failure or complications before extending duration.

When to switch from amoxicillin to amoxicillin-clavulanate

Amoxicillin-clavulanate (Augmentin) adds clavulanic acid, a beta-lactamase inhibitor, to amoxicillin. Beta-lactamase is an enzyme produced by some bacteria (including 30 to 40% of H. influenzae and nearly all Moraxella catarrhalis) that breaks down amoxicillin before it can kill the bacteria.

The 2012 IDSA guidelines recommend amoxicillin-clavulanate rather than amoxicillin alone as empiric first-line therapy for both adults and children, and reserve the high-dose formulation for specific situations (Chow et al., Clinical Infectious Diseases 2012):

Indications for high-dose amoxicillin-clavulanate (2 g/125 mg twice daily in adults):

• Regions where 10% or more of S. pneumoniae is penicillin-nonsusceptible
• Severe infection
• Daycare attendance, age under 2 or over 65, or recent hospitalization
• Antibiotic use within the past month, or immunocompromise

Standard dose: 875 mg/125 mg twice daily High dose: 2000 mg/125 mg (extended-release formulation) twice daily

The trade-off: amoxicillin-clavulanate causes more diarrhea than plain amoxicillin, and the clavulanic acid component is responsible for most of the added gastrointestinal side effects. An earlier version of this page gave rates of 10 to 25% versus 3 to 8% and attributed them to a Cochrane review; the percentages could not be traced to the cited paper (Gillies et al., CMAJ 2015) and have been removed.

Whether to start with amoxicillin-clavulanate or step up to it after plain amoxicillin fails is the prescriber's call: IDSA 2012 favors starting with amoxicillin-clavulanate, while AAO-HNS 2015 allows either. An earlier version of this page cited a 2011 cost-effectiveness analysis with a $47 saving; no such study could be found and it has been removed.

The pattern we see in telehealth consultations: patients requesting "the strongest antibiotic" at the first visit. The guideline-based approach is to follow IDSA 2012 or AAO-HNS 2015 rather than escalate on request, and to educate patients that "strongest" means "most likely to cause side effects," not "most effective."

The resistance decision tree: which dose for which patient

The choice between standard-dose, high-dose, and amoxicillin-clavulanate depends on local resistance patterns and patient-specific risk factors. Here's a decision tree built from the IDSA 2012 and AAO-HNS 2015 guidelines:

Step 1: Does the patient meet criteria for bacterial sinusitis?

• If no (symptoms less than 10 days, no severe features, no worsening), recommend watchful waiting.
• If yes, proceed to Step 2.

Step 2: Any risk factors for antibiotic resistance? Risk factors include:

• Antibiotic use within the past month
• Recent hospitalization
• Age under 2 or over 65
• Daycare attendance (children)
• Immunocompromise
• Living where 10% or more of S. pneumoniae is penicillin-nonsusceptible

• If no risk factors, IDSA 2012 recommends standard-dose amoxicillin-clavulanate (875/125 mg every 12 hours) for 5 to 7 days in adults; AAO-HNS 2015 also allows plain amoxicillin at the label dose for 5 to 10 days.
• If one or more risk factors, proceed to Step 3.

Step 3: Is the infection severe? Severe infection = fever 102°F or higher plus purulent discharge plus significant facial pain.

• With one or more risk factors, or severe infection, IDSA 2012 recommends high-dose amoxicillin-clavulanate (2 g/125 mg every 12 hours) for 5 to 7 days in adults.

Step 4: Reassess at 3 to 5 days.

• If improving, complete the course.
• If no improvement, switch to amoxicillin-clavulanate (if started on plain amoxicillin) or a respiratory fluoroquinolone like levofloxacin (if already on amoxicillin-clavulanate).
• If worsening, evaluate for complications (orbital cellulitis, meningitis, abscess) and consider imaging.

[Diagram suggestion: flowchart with decision nodes at each step, color-coded by treatment intensity (green = watchful waiting, yellow = standard amoxicillin, orange = high-dose amoxicillin, red = amoxicillin-clavulanate)]

This framework reduces unnecessary broad-spectrum antibiotic use while ensuring high-risk patients get adequate coverage from the start.

Common dosing errors and how to avoid them

Correction, September 2026: an earlier version of this page stated that 14% of amoxicillin prescriptions for sinusitis contained a dosing error, citing a 2019 study. No such finding exists in the cited author's work and it has been removed. Four mistakes worth avoiding:

Error 1: Assuming 500 mg twice daily is a mistake. It is not. The FDA label lists 500 mg every 12 hours as the usual adult dose for mild to moderate ear, nose and throat infections, and 875 mg every 12 hours or 500 mg every 8 hours for severe infections. Your prescriber chooses the regimen based on severity; do not change the frequency on your own.

Error 2: Extending treatment to 14 days reflexively. Unless the infection is complicated, 5 to 7 days is sufficient. Longer courses increase the risk of Clostridioides difficile infection and antibiotic resistance without improving cure rates.

Error 3: Not adjusting pediatric doses as the child grows. A 20 kg child who gains 5 kg over six months needs a dose increase from 450 mg to 562.5 mg twice daily at the AAP standard 45 mg/kg/day dose. Parents often continue the old dose because "it worked last time."

Error 4: Taking amoxicillin on an empty stomach and stopping due to nausea. Amoxicillin absorption is not significantly affected by food, and taking it with meals reduces gastrointestinal upset. The package insert allows for dosing with or without food.

How to avoid errors:

• Confirm the dose, frequency, and duration with the pharmacist when picking up the prescription.
• Set phone alarms for each dose to maintain even intervals.
• Write the schedule on the bottle in marker (e.g., "8 AM, 4 PM, midnight").
• Finish the course your prescriber set; the FDA label says treatment should continue for at least 48 to 72 hours after symptoms resolve.

Storage, missed doses, and early discontinuation warnings

Storage: amoxicillin capsules and tablets are stored at room temperature (68 to 77°F) in the original bottle. Keep the desiccant packet in the bottle. Amoxicillin suspension (liquid) must be refrigerated after reconstitution and discarded after 14 days. Do not freeze.

Missed dose protocol:

• Take a missed dose as soon as you remember, then return to your usual schedule.
• Do not double up doses to make up for a missed dose.
• The FDA label gives no hour cutoff for a missed dose; an earlier version of this page invented a 4-hour rule, which has been removed. Ask your pharmacist if you are unsure.

Missing more than two consecutive doses reduces the time above MIC and increases the risk of treatment failure. If you miss two or more doses, call your provider to discuss whether to extend the treatment duration.

Early discontinuation: stopping antibiotics early because "I feel better" is the single largest driver of antibiotic resistance in outpatient settings. Symptoms improve when bacterial counts drop below the threshold that triggers inflammation, but viable bacteria remain. Stopping treatment at that point allows resistant subpopulations to regrow.

The FDA label's rule is to continue treatment for a minimum of 48 to 72 hours beyond the time you become asymptomatic. An earlier version of this page cited a 2017 study reporting 34% higher recurrence after stopping early; that study could not be found and has been removed.

Shelf life after opening: amoxicillin capsules remain stable for the duration printed on the bottle (typically 2 to 3 years from manufacture) if stored properly. Suspension expires 14 days after reconstitution regardless of the printed date. Write the discard date on the bottle when you pick it up from the pharmacy.

When to call your provider about treatment failure

Treatment failure is defined as lack of improvement after 3 to 5 days of appropriate antibiotic therapy, or worsening at any point during treatment.

Call your provider within 24 hours if:

• Fever persists or worsens after 3 days of antibiotics
• Facial pain or headache intensifies despite treatment
• New symptoms develop (vision changes, severe headache, neck stiffness, confusion)
• Swelling around the eyes or redness of the eyelids (suggests orbital cellulitis, a medical emergency)
• Symptoms improve initially then worsen after stopping antibiotics

Red-flag symptoms requiring same-day evaluation or emergency care:

• Vision changes (double vision, decreased vision, eye pain with movement)
• Severe headache with vomiting
• Altered mental status or confusion
• Stiff neck with fever
• Swelling or redness of the forehead or cheek

These symptoms suggest extension of infection beyond the sinuses into the orbit or central nervous system. Such complications are rare: the 2018 Cochrane review recorded one serious complication (a brain abscess) among 3,057 trial participants (Lemiengre et al., 2018). They require IV antibiotics and often surgical drainage.

When to switch antibiotics: if symptoms are unchanged after 5 days of amoxicillin, the likely causes are:

1. Beta-lactamase-producing bacteria. Switch to amoxicillin-clavulanate.
2. Resistant pneumococcus. Switch to a respiratory fluoroquinolone (IDSA 2012 lists levofloxacin 500 mg daily or moxifloxacin).
3. Viral infection misdiagnosed as bacterial. Stop antibiotics and manage symptomatically.
4. Non-infectious cause. Consider allergic fungal sinusitis, vasculitis, or other non-bacterial etiologies.

Imaging (CT sinus) is not routinely indicated for uncomplicated sinusitis but should be obtained if symptoms persist beyond 4 weeks, if complications are suspected, or if the patient has recurrent infections (4 or more episodes per year).

When you should NOT use amoxicillin for a sinus infection

The strongest argument against amoxicillin in specific clinical scenarios:

Penicillin allergy. Patients with a documented IgE-mediated reaction to penicillin (hives, angioedema, anaphylaxis) should not receive amoxicillin. The cross-reactivity rate between penicillins and cephalosporins is 2 to 3%, lower than previously thought, so third-generation cephalosporins (cefdinir, cefpodoxime) are often safe alternatives (Pongdee et al., Mayo Clinic Proceedings 2018). Respiratory fluoroquinolones (levofloxacin, moxifloxacin) are penicillin-free options but carry black-box warnings for tendon rupture and QT prolongation.

Recent amoxicillin failure. If a patient was treated with amoxicillin for sinusitis within the past 3 months and experienced treatment failure or early recurrence, prescribing amoxicillin again selects for the same resistant organisms. Switch to amoxicillin-clavulanate or a fluoroquinolone.

Mononucleosis. Amoxicillin causes a characteristic maculopapular rash in a high proportion of patients with infectious mononucleosis (caused by Epstein-Barr virus); older case series reported it in most patients, and the exact rate is debated. The rash is not a true allergy but a T-cell-mediated reaction specific to the combination of amoxicillin and active EBV infection (Patel et al., American Family Physician 2007). If a patient presents with severe sore throat, fever, and fatigue, obtain a monospot test before prescribing amoxicillin.

Chronic sinusitis. Amoxicillin is effective for acute bacterial sinusitis but not for chronic rhinosinusitis (symptoms lasting 12 weeks or longer). Chronic sinusitis is usually polymicrobial, often includes anaerobes and Staphylococcus aureus, and frequently has a biofilm component that makes bacteria 1000-fold less susceptible to antibiotics (Psaltis et al., Laryngoscope 2008). Treatment requires longer courses of broader-spectrum antibiotics, nasal corticosteroids, saline irrigation, and often functional endoscopic sinus surgery.

Viral upper respiratory infection. The majority of "sinus infections" are viral. Prescribing amoxicillin for symptoms lasting less than 10 days without severe features exposes the patient to side effects (diarrhea, rash, yeast infections) and contributes to population-level antibiotic resistance without clinical benefit. In the 2018 Cochrane review, the number needed to treat for one additional cure with antibiotics in clinically diagnosed acute rhinosinusitis was 19 (95% CI 10 to 205), and the number needed to harm for one additional patient with side effects was 8 (95% CI 6 to 12) (Lemiengre et al., 2018).

A thoughtful clinician might argue that the harms of overtreatment (resistance, C. difficile, allergic reactions) outweigh the modest benefits of antibiotics in low-risk sinusitis, and that the default should be watchful waiting with a delayed prescription strategy (write the prescription but instruct the patient to fill it only if symptoms don't improve in 7 days). In a 2014 BMJ trial of 889 patients with respiratory infections, only 26 to 39% of those given a delayed prescription used antibiotics, versus 97% of those given an immediate prescription, with no difference in symptom severity (Little et al., BMJ 2014).

Correction and guideline check, September 2026

Correction, September 2026: an earlier version of this page attributed plain-amoxicillin regimens to the IDSA 2012 guideline, described 500 mg twice daily as underdosing, and cited several studies (a 2011 cost analysis, a 2014 adherence study, a 2017 recurrence study and a 2019 prescribing-error study) with figures that could not be traced to any published source. Those claims have been removed and the dosing text now follows the FDA amoxicillin label (DailyMed SPL published September 2, 2026), the IDSA 2012 guideline (Chow et al.), the AAO-HNS 2015 adult sinusitis guideline (Rosenfeld et al.) and the AAP 2013 pediatric guideline (Wald et al.).

Guideline check, September 5, 2026: IDSA 2012, AAO-HNS 2015 and AAP 2013 remain the current US guidelines for acute bacterial sinusitis. The 2018 Cochrane review (Lemiengre et al.) is the current systematic review of antibiotics versus placebo. If any of these is updated, this page will be revised.

FAQ

What is the standard amoxicillin dose for a sinus infection in adults?

The FDA label lists 500 mg every 12 hours or 250 mg every 8 hours for mild to moderate ear, nose and throat infections, and 875 mg every 12 hours or 500 mg every 8 hours for severe infections. IDSA 2012 recommends 5 to 7 days in adults and prefers amoxicillin-clavulanate as first-line; AAO-HNS 2015 allows amoxicillin with or without clavulanate for 5 to 10 days.

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

Most patients notice symptom improvement within 3 to 5 days. Fever typically resolves within 48 to 72 hours. If symptoms are unchanged after 5 days, contact your provider to discuss switching antibiotics.

Can I take 500 mg of amoxicillin twice a day for a sinus infection?

Yes, if that is what your prescriber ordered. The FDA amoxicillin label lists 500 mg every 12 hours as the usual adult dose for mild to moderate ear, nose and throat infections. For severe infections the label lists 875 mg every 12 hours or 500 mg every 8 hours. An earlier version of this answer called 500 mg twice daily underdosing; that was wrong.

What is the pediatric dose of amoxicillin for sinus infections?

Under the AAP 2013 guideline, children receive 45 mg/kg/day as the standard dose or 80 to 90 mg/kg/day as the high dose, divided into two doses, with a maximum of 2 g per dose. The FDA label lists 25 mg/kg/day for mild to moderate ear, nose and throat infections and 45 mg/kg/day for severe ones. A 20 kg child on 45 mg/kg/day takes 450 mg twice daily.

Should I take amoxicillin with food?

Amoxicillin can be taken with or without food. Taking it with meals reduces nausea and stomach upset but does not significantly affect absorption. If you experience gastrointestinal side effects, take it with food.

What if I miss a dose of amoxicillin?

Take the missed dose as soon as you remember, then go back to your usual schedule, and do not double up. The FDA label does not set an hour cutoff; if the next dose is very close, ask your pharmacist whether to skip the missed one.

Is 5 days of amoxicillin enough for a sinus infection?

Usually yes for adults with uncomplicated acute bacterial sinusitis. A 2009 meta-analysis of 12 trials (4,430 patients) found 3 to 7 day courses matched 6 to 10 day courses for clinical success (Falagas et al., BJCP 2009), and IDSA 2012 recommends 5 to 7 days in adults. IDSA recommends 10 to 14 days in children.

When should I switch from amoxicillin to Augmentin?

IDSA 2012 recommends starting with amoxicillin-clavulanate (Augmentin) rather than plain amoxicillin. If you started on plain amoxicillin, guidelines suggest reassessing after 3 to 5 days without improvement, and using the high-dose amoxicillin-clavulanate regimen when the infection is severe or you have risk factors such as antibiotic use in the past month. Augmentin covers beta-lactamase-producing bacteria that plain amoxicillin misses.

Can I drink alcohol while taking amoxicillin?

Moderate alcohol consumption does not reduce amoxicillin's effectiveness or cause dangerous interactions. However, alcohol can worsen dehydration and delay recovery from the infection. Avoid heavy drinking during treatment.

Why did my doctor prescribe 875 mg instead of 500 mg?

The FDA label lists 875 mg every 12 hours and 500 mg every 8 hours as the two regimens for severe infections, and 500 mg every 12 hours for mild to moderate ones. So 875 mg twice daily usually means your prescriber judged the infection severe or preferred a twice-daily schedule. Both are label doses.

What are the most common side effects of amoxicillin?

The FDA label lists diarrhea, nausea, vomiting and rash among the most common adverse reactions, along with vaginal yeast infections and, rarely, serious allergic reactions (hives, difficulty breathing, swelling) that need emergency care. An earlier version of this answer gave percentages that were not from the label; they have been removed.

How do I know if my sinus infection is bacterial and needs antibiotics?

Bacterial sinusitis is likely if symptoms last 10 days or more without improvement, if you have high fever (102°F or higher) with severe facial pain and purulent discharge for 3 to 4 days, or if symptoms worsen after initial improvement (double-sickening pattern). Most sinus infections lasting less than 10 days are viral.

Is amoxicillin or Augmentin the first choice for a sinus infection?

It depends on which guideline your prescriber follows. The IDSA 2012 guideline (Chow et al.) recommends amoxicillin-clavulanate (Augmentin) rather than amoxicillin alone as empiric first-line therapy for adults and children. The AAO-HNS 2015 adult guideline (Rosenfeld et al.) allows amoxicillin with or without clavulanate for 5 to 10 days, and the AAP 2013 guideline (Wald et al.) takes the same either-or position for children. Both drugs are reasonable; Augmentin adds coverage of beta-lactamase-producing bacteria at the cost of more diarrhea.

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• Tool: dosage calculator

Sources

1. Rosenfeld RM et al. Clinical practice guideline (update): adult sinusitis. Otolaryngology - Head and Neck Surgery. 2015. https://europepmc.org/article/MED/25832968
2. Chow AW et al. IDSA clinical practice guideline for acute bacterial rhinosinusitis in children and adults. Clinical Infectious Diseases. 2012. https://europepmc.org/article/MED/22438350
3. Wald ER et al. Clinical practice guideline for the diagnosis and management of acute bacterial sinusitis in children aged 1 to 18 years. Pediatrics. 2013. https://europepmc.org/article/MED/23796742
4. Gillies M et al. Common harms from amoxicillin: a systematic review and meta-analysis of randomized placebo-controlled trials for any indication. Canadian Medical Association Journal. 2015.
5. Pongdee T et al. Evaluation and management of penicillin allergy. Mayo Clinic Proceedings. 2018.
6. Patel BM et al. Amoxicillin rash in patients with infectious mononucleosis. American Family Physician. 2007.
7. Psaltis AJ et al. The effect of bacterial biofilms on antibiotic susceptibility in vitro. Laryngoscope. 2008.
8. Little P et al. Delayed antibiotic prescribing strategies for respiratory tract infections in primary care. BMJ. 2014. https://europepmc.org/article/MED/24603565
9. U.S. FDA via DailyMed. Amoxicillin capsules prescribing information (SPL published September 2, 2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5a660370-9a81-33f9-e063-6394a90a6c62
10. Lemiengre MB et al. Antibiotics for acute rhinosinusitis in adults. Cochrane Database of Systematic Reviews. 2018. https://europepmc.org/article/MED/30198548
11. Falagas ME et al. Effectiveness and safety of short vs. long duration of antibiotic therapy for acute bacterial sinusitis: a meta-analysis of randomized trials. British Journal of Clinical Pharmacology. 2009. https://europepmc.org/article/MED/19154447

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