Amoxicillin

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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Amoxicillin

C₁₆H₁₉N₃O₅S · 3H₂O 419.45

4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, 6-[[amino(4-hydroxyphenyl)acetyl]amino]-3,3-dimethyl-7-oxo-, trihydrate

[2S-[2α,5α,6β(S*)]]-;

(2S,5R,6R)-6-[(R)-(–)-2-Amino-2-(p-hydroxyphenyl)acetamido]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid trihydrate

CAS RN®: 61336-70-7; UNII: 804826J2HU.

Anhydrous 365.41

CAS RN®: 26787-78-0; UNII: 9EM05410Q9.

1 DEFINITION

Amoxicillin contains NLT 900 µg/mg and NMT 1050 µg/mg of amoxicillin (C₁₆H₁₉N₃O₅S), calculated on the anhydrous basis.

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020)

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

Procedure

Diluent:

6.8 g/L of monobasic potassium phosphate in water. Adjust with a 45% (w/w) solution of potassium hydroxide to a pH of 5.0 ± 0.1.

Mobile phase:

Acetonitrile and Diluent (1:24)

Standard solution:

1.2 mg/mL of USP Amoxicillin RS in Diluent.

[Note—Use this solution within 6 h.]

Sample solution:

1.2 mg/mL of Amoxicillin in Diluent.

[Note—Use this solution within 6 h.]

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 230 nm

Column: 4-mm × 25-cm; packing L1

Flow rate: 1.5 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

Suitability requirements:

Tailing factor: NMT 2.5

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate quantity, in µg/mg, of amoxicillin (C₁₆H₁₉N₃O₅S) in the portion of Amoxicillin taken:

Result = (rᵤ / rₛ) × (Cₛ / Cᵤ) × P

rᵤ = peak response from the Sample solution

rₛ = peak response from the Standard solution

Cₛ = concentration of USP Amoxicillin RS in the Standard solution (mg/mL)

Cᵤ = concentration of Amoxicillin in the Sample solution (mg/mL)

P = potency of Amoxicillin in USP Amoxicillin RS (µg/mg)

Acceptance criteria: 900–1050 µg/mg of amoxicillin (C₁₆H₁₉N₃O₅S) on the anhydrous basis

4 IMPURITIES

Organic Impurities

Solution A:

2.72 g/L monobasic potassium phosphate. Adjust with 1 N potassium hydroxide or 20% phosphoric acid to pH 5.0 ± 0.1.

Solution B:

Methanol

Mobile phase: See Table 1.

System suitability solution:

12.5 µg/mL each of USP Amoxicillin Related Compound A RS and USP Amoxicillin Related Compound D RS in Solution A

Standard solution:

12.5 µg/mL of USP Amoxicillin RS in Solution A

Sample solution:

1.25 mg/mL of Amoxicillin in Solution A

[Note—Store at 4° and use within 4 h.]

Chromatographic system

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm × 10-cm; 5-µm packing L1

Temperatures:

Autosampler: 4°

Column: 40°

Flow rate: 1.5 mL/min

Injection volume: 10 µL

System suitability

Samples: System suitability solution and Standard solution

[Note—Identify peaks by the relative retention times in Table 2.]

Suitability requirements:

Resolution: NLT 1.5 between amoxicillin related compound A and the second peak for amoxicillin related compound D

Relative standard deviation: NMT 10%, Standard solution

Analysis

Calculate percentage of each impurity:

Result = (rᵢ / rₛ) × (Cₛ / Cᵤ) × F × 100

rᵢ = impurity peak response (Sample)

rₛ = amoxicillin peak response (Standard)

Cₛ = concentration of USP Amoxicillin RS (µg/mL)

Cᵤ = concentration of Amoxicillin in Sample (mg/mL)

F = 0.001 mg/µg

TABLE 2

a (R)-2-Amino-2-(4-hydroxyphenyl)acetic acid.

b The chromatographic system resolves two penicilloic acids from each other.

c (4S)-2-{(R)-2-Amino-2-(4-hydroxyphenyl)acetamido

methyl}-5,5-dimethylthiazolidine-4-carboxylic acid.

d (2S,5R,6R)-6-Amino-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid.

e These compounds are listed for information only and are not to be reported.

f (2S,5R,6R)-6-[(S)-2-Amino-2-(4-hydroxyphenyl)acetamido]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid.

g (2S,5R,6R)-6-{(R)-2-[(R)-2-Amino-2-(4-hydroxyphenyl)acetamido]-2-(4-hydroxyphenyl)acetamido}-3,3-dimethyl-7-oxo-4-thia-1-

azabicyclo[3.2.0]heptane-2-carboxylic acid.

h The chromatographic system resolves two penilloic acids from each other.

i (4S)-2-{[(R)-2-Amino-2-(4-hydroxyphenyl)acetamido]methyl}-5,5-dimethylthiazolidine-4-carboxylic acid.

j (2S,5R,6R)-6-(2-[(R)-2-Amino-2-(4-hydroxyphenyl)acetamido]-2-((4S)-4-carboxy-5,5-dimethylthiazolidin-2-yl)acetamido)-3,3-

dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid.

k 3-(4-Hydroxyphenyl)pyrazin-2-ol.

l (4S)-2-[5-(4-Hydroxyphenyl)-3,6-dioxopiperazin-2-yl]-5,5-dimethylthiazolidine-4-carboxylic acid.

m (2S,5R,6R)-6-((2R)-2-{2-[(R)-2-Amino-2-(4-hydroxyphenyl)acetamido]-2-[(4S)-4-carboxy-5,5-dimethylthiazolidin-2-yl]acetamido}-

2-(4-hydroxyphenyl)acetamido)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid.

n (2S,5R,6R)-6-{(2S,5R,6R)-6-[(R)-2-Amino-2-(4-hydroxyphenyl)acetamido]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-

carboxamido}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid.

5 SPECIFIC TESTS

Crystallinity 〈695〉: Meets the requirements

Dimethylaniline 〈223〉: Meets the requirements

pH 〈791〉

Sample solution: 2 mg/mL

Acceptance criteria: 3.5–6.0

Water Determination 〈921〉, Method I: 11.5%–14.5%

Sterility Tests 〈71〉

Where the label states that Amoxicillin is sterile, it meets the requirements, except to use:

— Fluid Thioglycollate Medium containing Polysorbate 80 solution (5 mg/mL)

— Soybean-Casein Digest Medium containing polysorbate 80 solution (5 mg/mL)

— Sufficient sterile penicillinase to inactivate amoxicillin

— Shake tubes once daily

Bacterial Endotoxins Test 〈85〉:

If sterile or intended for injectable processing → NMT 0.25 USP EU/mg amoxicillin

6 ADDITIONAL REQUIREMENTS

Packaging and Storage:

Preserve in tight containers; store at controlled room temperature.

Labeling:

If intended for preparing injectable dosage forms:

— label states veterinary use only

— label states sterile or must undergo further processing

All other Amoxicillin:

— label states for manufacture of nonparenteral drugs only

USP Reference Standards 〈11〉

USP Amoxicillin RS

USP Amoxicillin Related Compound A RS

(2S,5R,6R)-6-Amino-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid

6-Aminopenicillanic acid

C₈H₁₂N₂O₃S 216.26

USP Amoxicillin Related Compound D RS

(4S)-2-{(R)-2-Amino-2-(4-hydroxyphenyl)acetamido

methyl}-5,5-dimethylthiazolidine-4-carboxylic acid

Amoxicillin open ring

C₁₆H₂₁N₃O₆S 383.42