Penicillins with extended spectrum
ATC code: J01CA04 (Amoxicillin)
Brand names
Amoxil, Moxatag
Beta-lactam antibiotic. Binds penicillin-binding proteins in the bacterial cell wall, inhibits transpeptidase, and disrupts peptidoglycan synthesis. Active against gram-positive organisms (Streptococcus pneumoniae, S. pyogenes, Enterococcus), select gram-negatives (beta-lactamase-negative H. influenzae, E. coli, Salmonella), and anaerobes. Susceptible to beta-lactamases, so in high-resistance regions it is combined with clavulanic acid.
First line
Drug of choice in adults and children when bacterial etiology is suspected per 2012 and . Adults: amoxicillin 500 mg TID or 875 mg BID for 5–7 days. In regions with high S. pneumoniae resistance or with risk factors, amoxicillin/clavulanate is used. Indications for antibiotics: symptoms over 10 days, worsening after initial improvement, severe onset with fever ≥ 39 °C and purulent discharge.
Sources
First line
In children with acute otitis media, amoxicillin 80–90 mg/kg/day in two divided doses for 5–10 days (depending on age and severity) is first-line per 2013. Children under 2 years with bilateral or severe disease receive antibiotics immediately. In milder unilateral cases in children over 2 years, 48–72 hour watchful waiting with a delayed prescription is acceptable.
First line
In outpatients without comorbidity or resistant pathogen risk factors, amoxicillin 1 g TID for 5 days is first-line per /ATS 2019 and . With comorbidity or risk factors: amoxicillin/clavulanate or a respiratory fluoroquinolone. In severe cases or suspected atypical organisms, a macrolide or doxycycline is added.
First line
A core component of eradication regimens per Maastricht VI/Florence Consensus 2022. First-line empirical options include bismuth-based quadruple therapy (PPI + bismuth + tetracycline + metronidazole, amoxicillin not used), triple therapy with amoxicillin (PPI + clarithromycin + amoxicillin 1 g BID), and in regions with clarithromycin resistance above 15 %, bismuth quadruple or levofloxacin-based regimens with amoxicillin are preferred.
First line
GAS pharyngitis confirmed by rapid antigen test or culture requires antibiotic therapy to prevent acute rheumatic fever. Per 2012, adults receive amoxicillin 500 mg every 12 hours or 1000 mg once daily; children receive 50 mg/kg once daily (max 1000 mg). Course duration is 10 days. Alternatives: penicillin V, cephalexin. Macrolides are reserved for beta-lactam allergy given rising resistance.
Not recommended
Acute viral respiratory illness is an indication where amoxicillin and all other antibiotics should not be used. The etiology is viral; antibiotics do not shorten symptoms, do not prevent bacterial complications, and increase the risk of adverse effects and antimicrobial resistance. and explicitly recommend against antibiotics in viral URI.
3 pairs found. Sorted from critical to minor.
Mechanism
Broad-spectrum antibiotics eliminate gut flora that synthesize vitamin K2 – reducing vitamin K availability for hepatic γ-carboxylation. INR rises 3–7 days after antibiotic initiation. The effect is most pronounced in patients on a low-vitamin-K diet.
Management
Check INR on days 3 and 7 of the antibiotic course, and again 7–10 days after completion. For courses ≥ 7 days, pre-emptively reduce the warfarin dose by 10–20 % and titrate by INR.
Sources
Mechanism
Amoxicillin can interfere with intestinal absorption of levothyroxine when taken simultaneously – clinically insignificant when administration is separated.
Management
Take levothyroxine and amoxicillin at least 2 hours apart.
Sources
Mechanism
A target combination in triple/quadruple Helicobacter pylori eradication regimens (Maastricht VI / Florence Consensus 2022, Kyoto Global Consensus, Russian Ministry of Health 2024 guidelines). No direct pharmacokinetic interaction – the two drugs act synergistically against H. pylori.
Management
Standard regimen: omeprazole 20 mg twice daily + amoxicillin 1000 mg twice daily + metronidazole (or clarithromycin) 500 mg twice daily for 14 days.
Sources
FDA category B. Cohort studies have not shown increased birth defect risk. Used in all trimesters when indicated.
Compatible with breastfeeding. Passes into milk in minimal amounts. Monitor the infant for diarrhea and sensitization.
amoxicillin is evaluated for the following indications with varying evidence strength: Community-acquired pneumonia (evidence tier A), Acute otitis media in children (evidence tier A), Helicobacter pylori infection (evidence tier A). See the full indication matrix with dosing and citations above on this page.
Common side effects of amoxicillin (≥ 1 in 100): Diarrhea (often self-limited), Nausea, vomiting, Oral and vaginal candidiasis, Skin rash. See the Safety section for uncommon and serious reactions.
FDA category B. FDA category B. Cohort studies have not shown increased birth defect risk. Used in all trimesters when indicated.
Compatible with breastfeeding. Passes into milk in minimal amounts. Monitor the infant for diarrhea and sensitization.
amoxicillin is contraindicated in: Immediate hypersensitivity to penicillins and other beta-lactams (anaphylaxis, angioedema, bronchospasm); Infectious mononucleosis (relative, due to frequent rash). Full list in the Safety section.
fever is a marker of infection of any kind, including viral. The decision to prescribe antibiotics is based on suspected etiology and clinical picture, not on temperature.
antibiotics affect gut microbiota but do not suppress immunity. When indicated, their use is necessary.
routine probiotic co-prescription with antibiotics lacks sufficient evidence of benefit in adults without specific C. difficile risk factors.