How many times a day should i take amoxicillin for a sinus infection?

Standard Dosing for Amoxicillin in Sinus Infections

Adults typically take amoxicillin three times a day (every 8 hours) for acute bacterial sinusitis, with a common dose of 500 mg per tablet. Treatment usually lasts 5-10 days, depending on severity and response.[1][2]

Children are dosed by weight: 45-90 mg/kg/day divided into two or three doses (every 12 or 8 hours).[1][3]

Factors That Affect Dosing Frequency

• High-dose regimens: For resistant infections, 875 mg twice a day (every 12 hours) is sometimes used instead.[2][4]
  
• Age and weight: Kids under 3 months or with kidney issues may need adjusted schedules.[3]
  
• Form: Suspension for kids is often twice daily; tablets for adults lean toward three times.[1]
  
  Always follow your prescription—do not self-adjust.
  
  

Why Three Times a Day Is Common

Amoxicillin has a short half-life (about 1-1.5 hours), so spacing doses maintains steady blood levels to fight bacteria like Streptococcus pneumoniae in sinuses.[4][5] Twice-daily options like amoxicillin-clavulanate (Augmentin) improve adherence but aren't plain amoxicillin.[2]

What If I Miss a Dose or Take Too Many?

Take the missed dose as soon as possible unless it's near the next one—then skip it. Overdose risks nausea, vomiting, or diarrhea; seek emergency care if severe.[1][6] Space doses evenly around the clock, even overnight.

Common Side Effects and When to Contact a Doctor

Diarrhea (most frequent), nausea, rash. Stop and call your doctor for allergic reactions (hives, swelling, breathing issues) or worsening sinus symptoms after 3 days.[1][2][5] Probiotics can help gut issues from antibiotics.

Alternatives If Amoxicillin Isn't Right

• Augmentin (amoxicillin + clavulanate): Twice daily, better for beta-lactamase producers.[2]
  
• Doxycycline or levofloxacin: Once or twice daily for penicillin-allergic patients.[4]
  Guidelines favor amoxicillin first-line unless allergies or resistance suspected.[5]
  
  Sources
  [1]: MedlinePlus - Amoxicillin
  [2]: UpToDate - Acute sinusitis treatment
  [3]: AAP Red Book - Amoxicillin dosing
  [4]: IDSA Guidelines - Sinusitis
  [5]: Drugs.com - Amoxicillin
  [6]: FDA Label - Amoxicillin