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Ampicillin
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C16H19N3O4S (anhydrous) 349.41

4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, [6-(aminophenylacetyl)amino]-3,3-dimethyl-7-oxo-, [2S-[2,5,6(S*)]]-.

(2S,5R,6R)-6-[(R)-2-Amino-2-phenylacetamido]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid. [69-53-4].

Trihydrate 403.46 [7177-48-2].
» Ampicillin is anhydrous or contains three molecules of water of hydration. It contains not less than 900 µg and not more than 1050 µg of C16H19N3O4S per mg, calculated on the dried basis.
Packaging and storage— Preserve in tight containers.
Labeling— Label it to indicate whether it is anhydrous or is the trihydrate. Where the quantity of ampicillin is indicated in the labeling of any preparation containing Ampicillin, this shall be understood to be in terms of anhydrous ampicillin (C16H19N3O4S). Where it is intended for use in preparing injectable dosage forms, the label states that it is the trihydrate and that it is sterile or must be subjected to further processing during the preparation of injectable dosage forms.
Identification, Infrared Absorption 197K , except that where the specimen under test is the trihydrate, both it and the USP Ampicillin Trihydrate RS are undried.
Crystallinity 695: meets the requirements.
Bacterial endotoxins 85— Where the label states that Ampicillin is sterile or must be subjected to further processing during the preparation of injectable dosage forms, it contains not more than 0.15 USP Endotoxin Unit per mg of ampicillin.
Sterility 71— Where the label states that Ampicillin is sterile, it meets the requirements when tested as directed for Membrane Filtration under Test for Sterility of the Product to be Examined, except to dissolve 6 g in 800 mL of Fluid D containing sufficient sterile penicillinase to inactivate the ampicillin and to swirl the vessel until solution is complete before filtering.
pH 791: between 3.5 and 6.0, in a solution containing 10 mg per mL.
Water, Method I 921: not more than 2.0% where it is labeled as Ampicillin (anhydrous); between 12.0% and 15.0% where it is labeled as Ampicillin (trihydrate).
Dimethylaniline 223: meets the requirement.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
Mobile phase— Prepare a suitable filtered and degassed mixture of water, acetonitrile, 1 M monobasic potassium phosphate, and 1 N acetic acid (909:80:10:1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Diluent— Mix 10 mL of 1 M monobasic potassium phosphate and 1 mL of 1 N acetic acid, dilute with water to 1000 mL, and mix.
Standard preparation— Dissolve a suitable quantity of USP Ampicillin RS, accurately weighed, in Diluent to obtain a solution having a known concentration of about 1 mg per mL, using shaking and sonication, if necessary, to achieve complete dissolution. Use this solution promptly after preparation.
Assay preparation— Transfer an accurately weighed quantity of Ampicillin, equivalent to about 100 mg of anhydrous ampicillin, to a 100-mL volumetric flask, add about 75 mL of Diluent, shake and sonicate, if necessary, to achieve complete dissolution, dilute with Diluent to volume, and mix. Use this solution promptly after preparation.
Resolution solution— Dissolve caffeine in Standard preparation to obtain a solution containing about 0.12 mg per mL.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector, a 4-mm × 5-cm pre-column containing 5- to 10-µm packing L1, and a 4-mm × 30-cm analytical column containing 5- to 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between the caffeine and the ampicillin peaks is not less than 2.0. The relative retention times are about 0.5 for ampicillin and 1.0 for caffeine. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the capacity factor, k¢, is not more than 2.5, the tailing factor is not more than 1.4, and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of ampicillin (C13H19NO4S) in each mg of the Ampicillin taken by the formula:
100(CP / W)(rU / rS),
in which C is the concentration, in mg per mL, of USP Ampicillin RS in the Standard preparation; P is the potency, in µg of ampicillin per mg, of USP Ampicillin RS; W is the weight, in mg, of Ampicillin taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Staff Liaison : Brian D. Gilbert, Ph.D., Scientist
Expert Committee : (MDANT05) Monograph Development-Antibiotics
USP29–NF24 Page 165
Pharmacopeial Forum : Volume No. 28(6) Page 1766
Phone Number : 1-301-816-8223