Amoxicillin

Amoxicillin is first-line for acute bacterial rhinosinusitis when an antibiotic is chosen: in adults per AAO-HNS 2015 (Amoxicillin with or without clavulanate), in children per AAP 2013 and the Spanish SEIP/AEPap consensus 2023. Guidelines differ: IDSA 2012 prefers Amoxicillin/clavulanate empirically, and NICE NG79 (2017) lists Phenoxymethylpenicillin first and does not mention Amoxicillin. An antibiotic is considered when symptoms last more than 10 days without improvement, worsen after initial improvement, or start severely (fever of 39 °C or higher with purulent discharge or facial pain for 3–4 consecutive days); before that no antibiotic is needed, and AAO-HNS and NICE allow watchful waiting or a delayed prescription. The benefit is modest: in the Cochrane 2014 review 91% were cured or improved on penicillin or Amoxicillin versus 86% on placebo, with more adverse events. The standard adult dose is 500 mg three times daily for 5–10 days per AAO-HNS 2015 (NICE: 5 days); an 875 mg strength is not marketed in Spain. Children: 45 mg/kg/day, 80–90 mg/kg/day with risk factors (AAP 2013), 10–14 days per IDSA. High-dose Amoxicillin/clavulanate is used where non-susceptible S. pneumoniae exceeds 10%, at age 65 or older, after recent hospitalisation or an antibiotic in the last month, and with immunosuppression. Eyelid swelling, visual change, severe headache or neck stiffness need urgent in-person assessment. Per the label, it is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; AAO-HNS and NICE suggest Doxycycline for allergic patients. Avoid Amoxicillin if infectious mononucleosis is suspected (rash); antibiotic-associated colitis can occur. In pregnancy it is used when benefit outweighs risk; small amounts pass into breast milk. Interactions: Methotrexate (increased toxicity), oral anticoagulants (monitor prothrombin time), Allopurinol (more rash).

ICD-10: J01.9 · ICD-11: CA01

In children with acute otitis media, Amoxicillin is the first-choice antibiotic per AAP 2013, NICE NG91 (2018, updated 2022) and the Spanish SEIP/AEPap consensus 2023. Pain relief with Paracetamol or Ibuprofen is the basis of treatment. Antibiotics are started at once for moderate or severe disease (severe pain, fever of 39 °C or higher, otorrhoea) and, per AAP 2013, for bilateral disease at 6–23 months; for non-severe disease from 6 months of age, 48–72 hours of observation with a delayed prescription is acceptable. Dosing depends on the guideline: AAP 2013 and the 2023 consensus use high-dose Amoxicillin (80–90 mg/kg/day, in two doses per AAP), NICE NG91 uses standard age-based doses three times daily. Course: 5–7 days for uncomplicated disease (NICE, 2023 consensus), up to 10 days under 2 years or with severe disease (AAP). Amoxicillin/clavulanate is used if Amoxicillin was given in the last 30 days, with purulent conjunctivitis, or with a history of recurrent otitis that did not respond to Amoxicillin. Cochrane 2023 found a modest reduction in pain with antibiotics and more vomiting, diarrhoea and rash. Per the label, Amoxicillin is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; NICE suggests Clarithromycin for allergic children. Avoid Amoxicillin if infectious mononucleosis is suspected (morbilliform rash). Antibiotic-associated colitis can occur. Interactions: Methotrexate (increased toxicity), Allopurinol (more rash), oral anticoagulants (monitor prothrombin time).

ICD-10: H66.0 · ICD-11: AB00

Amoxicillin is the first-choice antibiotic for non-severe community-acquired pneumonia in adults treated as outpatients who have no chronic comorbidity and no risk factors for MRSA (methicillin-resistant Staphylococcus aureus) or Pseudomonas: ATS/IDSA 2019 recommend 1 g three times daily for at least 5 days and until clinical stability, NICE NG250 (2025) recommends 500 mg three times daily (higher doses can be used) for 5 days. Amoxicillin does not cover atypical pathogens (Mycoplasma, Legionella, Chlamydophila), so NICE adds Clarithromycin when they are suspected. With chronic comorbidity, ATS/IDSA suggest Amoxicillin/clavulanate or a cephalosporin combined with a macrolide or Doxycycline, or a respiratory fluoroquinolone alone; severe pneumonia is treated in hospital with parenteral regimens. The short course is supported by meta-analyses (Tansarli 2018, Furukawa 2023) and by the El Moussaoui 2006 RCT, in which 3 days of Amoxicillin was non-inferior to 8 days in hospitalised patients with non-severe pneumonia. In children with non-severe pneumonia Amoxicillin is also first choice (NICE NG250, Spanish AEP/SEIP consensus 2015). Per the label, it is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; for allergic patients NICE suggests Doxycycline or Clarithromycin. Avoid Amoxicillin if infectious mononucleosis is suspected (rash); antibiotic-associated colitis can occur; reduce the dose in severe renal impairment. In pregnancy it is used when benefit outweighs risk; small amounts pass into breast milk and the infant may develop diarrhoea or candidiasis. Interactions: Methotrexate (increased toxicity), oral anticoagulants (monitor prothrombin time), Allopurinol (more rash).

ICD-10: J18.9 · ICD-11: CA40.Z

Amoxicillin is part of most eradication regimens, but it is no longer the empirical first line in Spain. Where clarithromycin resistance is above 15% or unknown (the Spanish situation), Maastricht VI/Florence 2022, ACG 2024 and the VI Spanish consensus 2026 give bismuth quadruple therapy as first line, without Amoxicillin: a proton pump inhibitor (PPI, for example Omeprazole) + bismuth + Tetracycline + Metronidazole, 10 days per the VI consensus; Maastricht VI allows concomitant therapy (PPI + Amoxicillin + Clarithromycin + Metronidazole) when bismuth is unavailable. In the V Spanish consensus 2021 concomitant therapy with Amoxicillin was a first-line option alongside bismuth; in the VI consensus 2026 only the bismuth regimen remains first line. After failure of the bismuth regimen the standard is PPI + Amoxicillin + Levofloxacin + bismuth. Triple therapy with PPI + Clarithromycin + Amoxicillin (1 g twice daily) is appropriate only with proven clarithromycin susceptibility or local resistance below 15%. Per ACG 2024, Amoxicillin-containing regimens are an alternative in patients without penicillin allergy; allergic patients receive bismuth quadruple therapy. Eradication is confirmed by a breath test at least 4 weeks after treatment. Per the label, Amoxicillin is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; diarrhoea, rash and antibiotic-associated colitis can occur; avoid it if infectious mononucleosis is suspected. Interactions: Methotrexate (increased toxicity), oral anticoagulants (monitor prothrombin time), Allopurinol (more rash); in Clarithromycin-containing regimens the main interactions (statins, QT prolongation) come from Clarithromycin. In pregnancy Amoxicillin is used when benefit outweighs risk; Tetracycline from the bismuth regimen is contraindicated in pregnancy.

ICD-10: B98.0 · ICD-11: DA42.1

For early Lyme disease with erythema migrans, IDSA/AAN/ACR 2020 recommend Doxycycline, Amoxicillin or Cefuroxime axetil as equal options; Amoxicillin is given 500 mg three times daily for 14 days, in children 50 mg/kg/day in three doses. NICE NG95 (2018) lists Doxycycline first and Amoxicillin as the alternative at 1 g three times daily for 21 days; in pregnant women and children under 9, where Doxycycline is undesirable, Amoxicillin comes first. Amoxicillin is not used for prophylaxis after a tick bite: for high-risk bites a single dose of Doxycycline within 72 hours is used. Neurological, cardiac or joint involvement needs different regimens. The indication is in the Spanish label, which also describes a Jarisch-Herxheimer reaction at the start of Lyme treatment (fever, chills, worsening rash) that resolves on its own. Amoxicillin is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; avoid it if infectious mononucleosis is suspected (rash); antibiotic-associated colitis can occur. In pregnancy it is used when benefit outweighs risk; small amounts pass into breast milk. Interactions: Methotrexate (increased toxicity), oral anticoagulants (monitor prothrombin time), Allopurinol (more rash).

ICD-10: A69.2 · ICD-11: 1C1G

In group A Streptococcus (GAS) tonsillopharyngitis confirmed by rapid antigen test or culture, Amoxicillin and Penicillin V are equal antibiotics of choice per IDSA 2012 and the Spanish adult consensus (Cots 2015). NICE NG84, ESCMID 2012 and the Spanish paediatric SEIP/AEPap consensus 2020 prefer Penicillin V for its narrow spectrum; in children Amoxicillin is often chosen for the taste of the suspension and once-daily dosing (Lennon 2008 RCT: once-daily Amoxicillin was non-inferior to twice-daily Penicillin V). IDSA 2012 doses: 50 mg/kg once daily (max 1000 mg) or 25 mg/kg twice daily (max 500 mg) for 10 days; adults take these maximum doses. Cochrane 2021 shows that antibiotics shorten symptoms (sore throat on day 3, RR 0.70) and reduce acute otitis media, peritonsillar abscess and rheumatic fever, which is now rare in Europe; with a Centor score of 0–2 no antibiotic is needed (ESCMID 2012). In non-anaphylactic penicillin allergy a first-generation cephalosporin is used, in anaphylaxis a macrolide or Clindamycin. Per the label, Amoxicillin is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam. If infectious mononucleosis is suspected, which mimics streptococcal tonsillitis, Amoxicillin is not prescribed: it frequently causes a morbilliform rash. Diarrhoea, rash and antibiotic-associated colitis can occur. In pregnancy it is used when benefit outweighs risk; small amounts pass into breast milk. Interactions: Methotrexate (increased toxicity), Allopurinol (more rash), oral anticoagulants (monitor prothrombin time).

ICD-10: J02.0 · ICD-11: 1B51

In a dental abscess the basis of treatment is the dental procedure: drainage, endodontic treatment or extraction. ADA 2019 recommend against antibiotics for pulpitis and periapical abscess without swelling or systemic signs in immunocompetent adults: the benefit is negligible and harm is possible. An antibiotic is added to the procedure when there is swelling with signs of spreading infection (fever, malaise, increasing facial swelling, enlarged lymph nodes) or when dental care is not available: first choice is Amoxicillin 500 mg three times daily for 3–7 days or Penicillin V; without improvement in 2–3 days, Amoxicillin/clavulanate; in penicillin allergy, Azithromycin or Clindamycin. The Spanish label lists 'dental abscesses with spreading cellulitis'; the 2004 Spanish consensus of dental societies on odontogenic infections is the local reference, though dated. Trismus, difficulty swallowing or breathing, or swelling of the neck or eye require urgent hospital care. Amoxicillin is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; avoid it if infectious mononucleosis is suspected (rash); diarrhoea, rash and antibiotic-associated colitis can occur. In pregnancy it is used when benefit outweighs risk; small amounts pass into breast milk. Interactions: Methotrexate (increased toxicity), oral anticoagulants (monitor prothrombin time), Allopurinol (more rash).

ICD-10: K04.7

ESC 2023 recommend antibiotic prophylaxis before dental procedures involving gingival manipulation, the periapical region or mucosal perforation only for high-risk patients: prosthetic valve or prosthetic material, previous endocarditis, and selected congenital heart defects. Within this niche Amoxicillin is the drug of choice: 2 g orally as a single dose 30–60 minutes before the procedure (children 50 mg/kg); in penicillin allergy, Cephalexin (if no anaphylaxis), Azithromycin, Clarithromycin or Doxycycline, while ESC 2023 no longer advise Clindamycin because of colitis risk. Tier B rather than A: the benefit of prophylaxis itself rests on observational data only, there are no randomised trials, and NICE CG64 does not recommend routine prophylaxis; first line here is a reasoned niche, not a universal recommendation. Low- and intermediate-risk patients do not need prophylaxis; regular oral hygiene matters more for everyone. The indication is in the Spanish label. Amoxicillin is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; even a single dose can cause diarrhoea or rash. Interactions rarely matter with a single dose, but patients on oral anticoagulants, common among valve recipients, should know that prothrombin time may rise.

ICD-10: I33.0