What is the appropriate dosing of Amoxicillin (amoxicillin) for adults?

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DS

Dainyal Siddiqui, MD

Internal Medicine

MJ

Manuel Jimenez, MD

Cardiology

FP

Franz Pierre-Louis, MD

Infectious Disease

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Last updated: May 22, 2025 • View editorial policy

From the Guidelines

For adults, the recommended dosage of amoxicillin is 1 g every 8 hours, as this regimen has shown efficacy in treating community-acquired pneumonia and has a long track record of safety 1.

Amoxicillin Dosing Considerations

When determining the appropriate dosage of amoxicillin for adults, several factors should be considered, including the severity of the infection, the presence of comorbidities, and the risk of antibiotic resistance.

  • The total daily dose of amoxicillin can vary from 1.5 to 4 g/day, with lower daily doses (1.5 g/day) more appropriate for mild disease in patients with no risk factors for infection with a resistant pathogen 2.
  • Higher daily doses (4 g/day) may be advantageous in areas with a high prevalence of penicillin-resistant S pneumoniae or for patients with moderate disease, or for patients who may need better H influenzae coverage or for patients with risk factors for infection with a resistant pathogen 2.

Important Administration Instructions

  • Amoxicillin should be taken with or without food, and the full course should be completed even if symptoms improve before finishing.
  • Patients should be aware of potential side effects including diarrhea, nausea, and rash, and should seek immediate medical attention if experiencing signs of allergic reaction such as hives, difficulty breathing, or swelling.

Mechanism of Action and Efficacy

  • Amoxicillin works by inhibiting bacterial cell wall synthesis, making it effective against many gram-positive and some gram-negative bacteria.
  • However, increasing resistance means susceptibility testing is often important for optimal treatment 1.

From the FDA Drug Label

The usual adult dose is one 500 mg/125 mg amoxicillin and clavulanate potassium tablet every 12 hours or one 250 mg/125 mg amoxicillin and clavulanate potassium tablet every 8 hours For more severe infections and infections of the respiratory tract, the dose should be one 875 mg/125 mg amoxicillin and clavulanate potassium tablet every 12 hours or one 500 mg/125 mg amoxicillin and clavulanate potassium tablet every 8 hours

The recommended amoxicillin dosing for adults is:

  • 500 mg every 12 hours or 250 mg every 8 hours for typical infections
  • 875 mg every 12 hours or 500 mg every 8 hours for more severe infections and respiratory tract infections 3

From the Research

Amoxicillin Dosing for Adults

  • The dosing of amoxicillin for adults is not explicitly stated in the provided studies, but it can be inferred from the information on amoxicillin/clavulanate formulations 4, 5, 6, 7, 8.
  • A pharmacokinetically enhanced tablet dosage form of amoxicillin/clavulanate 2000/125 mg twice daily has been developed for use in adult respiratory tract infection due to drug-resistant pathogens 4.
  • Amoxicillin/clavulanate is available in different formulations, including adult formulations with a clavulanic acid dose restricted to 125 mg due to tolerability issues 5.
  • The combination of amoxicillin and clavulanic acid has been effective in treating various infections, including respiratory tract infections, urinary tract infections, and skin and soft tissue infections 6, 7.
  • The properties of oral amoxicillin and clavulanic acid, including their indications and usage, have been reviewed, with emphasis on the preferred use of amoxicillin alone 8.

Formulations and Dosage

  • Different ratios of amoxicillin to clavulanic acid are available, including 4:1, 2:1, 7:1, 14:1, and 16:1 8.
  • The choice of combination ratio and optimal oral administration of amoxicillin/clavulanate depend on various factors, including the type of infection and patient population 8.
  • Amoxicillin/clavulanate has been used as empiric therapy for many infectious syndromes, leading to extensive consumption, and guidance is needed on indications for amoxicillin versus amoxicillin/clavulanate 8.

Clinical Efficacy and Safety

  • Amoxicillin/clavulanate has demonstrated high clinical efficacy in treating various infections, including those caused by drug-resistant pathogens 4, 6, 7.
  • The combination has a well-known safety and tolerance profile, with gastrointestinal side effects being the most common adverse events 4, 6.
  • The use of amoxicillin/clavulanate has been associated with the emergence of resistance in some pathogens, and its use should be guided by susceptibility testing and clinical judgment 5, 8.

References

2
Guideline

antimicrobial treatment guidelines for acute bacterial rhinosinusitis.

Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery, 2004

8
Research

Oral amoxicillin and amoxicillin-clavulanic acid: properties, indications and usage.

Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases, 2020

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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