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Penicillin G Benzathine
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(C16H18N2O4S)2·C16H20N2·4H2O 981.19

4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, 3,3-dimethyl-7-oxo-6-[(phenylacetyl)amino-], 2[S-(2,5,6)]-, compd. with N,N¢-bis(phenylmethyl)-1,2-ethanediamine (2:1), tetrahydrate.

(2S,5R,6R)-3,3-Dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid compound with N,N¢-dibenzylethylenediamine (2:1), tetrahydrate [41372-02-5].

Anhydrous 909.15 [1538-09-6].
» Penicillin G Benzathine has a potency of not less than 1090 Penicillin G Units and not more than 1272 Penicillin G Units per mg.
Packaging and storage— Preserve in tight containers.
Labeling— Where it is intended for use in preparing injectable dosage forms, the label states that it is sterile or must be subjected to further processing during the preparation of injectable dosage forms.
Identification, Ultraviolet Absorption 197U—
Solution: 500 µg per mL.
Medium: methanol.
Absorptivity at 263 nm is between 85.0% and 110.0% of that of USP Penicillin G Benzathine RS.
Crystallinity 695: meets the requirements.
Bacterial endotoxins 85— Where the label states that Penicillin G Benzathine is sterile or that it must be subjected to further processing during the preparation of injectable dosage forms it contains not more than 0.01 USP Endotoxin Unit per 100 Penicillin G Units.
Sterility 71— Where the label states that Penicillin G Benzathine is sterile it meets the requirements when tested as directed in the section Direct Inoculation of the Culture Medium under Test for Sterility of the Product to be Examined, except to use Fluid Thioglycollate Medium and Soybean–Casein Digest Medium containing polysorbate 80 solution (1 in 200) and an amount of sterile penicillinase sufficient to inactivate the penicillin G in each tube, and to shake the vessels once daily.
pH 791: between 4.0 and 6.5, in a solution prepared by dissolving 50 mg in 50 mL of dehydrated alcohol, adding 50 mL of water, and mixing.
Water, Method I 921: between 5.0% and 8.0%.
Benzathine content— To about 1 g of Pencillin G Benzathine, accurately weighed, add 30 mL of a saturated solution of sodium chloride and 10 mL of 5 N sodium hydroxide, and extract with four 50-mL portions of ether. Wash the combined ether extracts with three 10-mL portions of water. Extract the combined water washings with 25 mL of ether, and add the ether extract to the water-washed combined ether extracts. Evaporate this combined ether solution to a volume of about 5 mL, add 2 mL of dehydrated alcohol, and evaporate to dryness. Dissolve the residue in 50 mL of glacial acetic acid, add 1 mL of p-naphtholbenzein TS, and titrate with 0.1 N perchloric acid VS to a green endpoint. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 12.02 mg of benzathine (C16H20N2): between 24.0% and 27.0% of benzathine in Penicillin G Benzathine, calculated on the anhydrous basis, is found.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
0.05 M phosphate buffer, pH 6.0— Dissolve 6.8 g of monobasic potassium phosphate in 900 mL of water, adjust with 1 N sodium hydroxide to a pH of 6.0, dilute with water to 1000 mL, and mix.
Mobile phase— Prepare a mixture of 0.05 M phosphate buffer, pH 6.0 and acetonitrile (4:1), pass through a membrane filter having a 5-µm or finer porosity, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation— Transfer about 40 mg of USP Penicillin G Potassium RS, accurately weighed, to a 50-mL volumetric flask, add 10 mL of acetonitrile and 5 mL of methanol, and swirl to dissolve. Without delay, dilute with 0.05 M phosphate buffer, pH 6.0 to volume, and mix.
System suitability preparation— Prepare a solution of penicillin V potassium in Mobile phase containing about 1 mg per mL. Mix equal volumes of this solution and the Standard preparation.
Assay preparation— Transfer about 53 mg of Penicillin G Benzathine, accurately weighed, to a 50-mL volumetric flask, add 10 mL of acetonitrile and 5 of methanol, and swirl to dissolve. Without delay, dilute with 0.05 M phosphate buffer, pH 6.0 to volume, and mix.
Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 225-nm detector and a 4-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation and the System suitability preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.7 for penicillin G and 1.0 for penicillin V; the resolution, R, between penicillin G and penicillin V is not less than 2.0; the column efficiency determined from the analyte peak is not less than 600 theoretical plates; and the relative standard deviation for replicate injections of the Standard preparation is not more than 1.0%.
Procedure— Separately inject equal volumes (about 10 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 potency, in Penicillin G Units per mg, of the Penicillin G Benzathine taken by the formula:
50(CP / W)(rU / rS),
in which C is the concentration, in mg per mL, of USP Penicillin G Potassium RS in the Standard preparation; P is the stated potency, in Penicillin G Units per mg, of USP Penicillin G Potassium RS; W is the quantity, in mg, of Penicillin G Benzathine taken to prepare the Assay preparation; and rU and rS are the penicillin G 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 1654
Phone Number : 1-301-816-8223