Amoxicillin

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Cat Number

API26787780

CAS Number

26787-78-0

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CAS Number

26787-78-0

EINECS

248-003-8

Storage

Store at 2-8℃

Synonyms

Amoxycillin; Amoxicillin anhydrous; Amoxicilline; Amopenixin; p-Hydroxyampicillin; D-Amoxicillin

Molecular Formula

C16H19N3O5S

Molecular Weight

365.4

Smiles

CC1([C@@H](N2[C@H](S1)[C@@H](C2=O)NC(=O)[C@@H](C3=CC=C(C=C3)O)N)C(=O)O)C

Appearance

White to off-white powder

Melting Point

140℃

Boiling Point

743.2±60.0℃

General Description

Amoxicillin is a broad-spectrum, semisynthetic aminopenicillin antibiotic with enhanced oral bioavailability compared to ampicillin. It is available in multiple formulations, including capsules, tablets, chewable tablets, and oral suspension, making it suitable for both adult and pediatric use. The drug is stable in gastric acid and is one of the most commonly prescribed antibiotics in ambulatory care.

Mechanism of Action

Amoxicillin exerts bactericidal activity by inhibiting bacterial cell wall synthesis through binding to penicillin-binding proteins (PBPs) located on the inner membrane of the bacterial cell wall. This binding inhibits the transpeptidation reaction required for cross-linking of peptidoglycan strands, disrupting the structural integrity of the cell wall. The resulting osmotic instability leads to bacterial lysis and death, primarily during active cell division.

Application

It is indicated for the treatment of infections caused by susceptible organisms, including otitis media, sinusitis, pharyngitis, community-acquired pneumonia, urinary tract infections, and skin and soft tissue infections. It is also used as prophylaxis against bacterial endocarditis in patients undergoing certain dental procedures. The addition of clavulanate extends its spectrum to cover beta-lactamase-producing organisms. Dosing requires adjustment in renal impairment, and hypersensitivity reactions are the most significant adverse effects.

In this comparative study of rescue treatments for Helicobacter pylori, bismuth quadruple therapy with furazolidone and tetracycline (BQFT) achieved significantly higher eradication rates (modified intention‑to‑treat: 96.2% vs. 76%; per‑protocol: 97.1% vs. 77.8%) than the amoxicillin‑containing regimen (BQFA). However, BQFA had fewer overall adverse effects (11.6% vs. 20.7%). Compliance and symptom improvement were similar. The authors conclude that BQFT offers superior efficacy with acceptable tolerability, making it a promising option for patients with multiple prior treatment failures, though the choice should weigh efficacy against side effect profile.

Fig. 1 Adverse effects of BQFT and BQFA. (Xie J, et al., 2025)

References

Xie J, et al. Efficacy and safety of tetracycline vs. amoxicillin in furazolidone-based rescue therapy for Helicobacter pylori: a real-world analysis. Ann Med. 2025; 57(1):2464938.

In a human study, metagenomic sequencing of gut microbiomes before and after antibiotic treatment revealed that azithromycin (a macrolide) produced clear, sustained reductions in Bifidobacterium species and significant increases in macrolide resistance genes. Amoxicillin did not induce comparable changes. Unrelated controls showed no such trends. The findings highlight that commonly overused antibiotics have differential impacts on the gut microbiome, with azithromycin specifically altering beneficial commensals and enriching for resistance determinants.

Fig. 2 Relative abundace of the dominant bacteriophage families over time and antibiotic treatment. (Chopyk J, et al., 2023)

References

Chopyk J, et al. Common antibiotics, azithromycin and amoxicillin, affect gut metagenomics within a household. BMC Microbiol. 2023; 23(1):206.

Does Amoxicillin require strict cold chain storage as a beta-lactam antibiotic?

Yes, it should be stored at 2-8°C for long-term stability. At room temperature, hydrolysis of the beta-lactam ring accelerates, leading to rapid potency loss.

Is Amoxicillin sensitive to moisture, and how is this prevented?

Extremely. It is hygroscopic and readily hydrolyzes. Our packaging includes moisture-barrier foil bags with desiccant, and we recommend storage in low-humidity conditions.

What visual changes indicate degradation of Amoxicillin?

Degradation may manifest as yellowing or browning of the powder, or clumping due to moisture absorption. If observed, the material should be tested for potency before use.

How is the impurity amoxicilloic acid monitored during stability?

This primary hydrolysis product is specifically quantified using a validated HPLC method, ensuring it remains below pharmacopoeial limits throughout the shelf life.