Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Sulfydryl donor; antidote to paracetamol poisoning; mucolytic.
DEFINITION
Acetylcysteine Injection is a sterile solution in Water for Injections of acetylcysteine sodium, prepared by the interaction of
Acetylcysteine with Sodium Hydroxide.
The injection complies with the requirements stated under Parenteral Preparations and with the following requirements.
Content of acetylcysteine, C5H9NO3S
95.0 to 105.0% of the stated amount.
IDENTIFICATION
To a volume containing the equivalent of 0.8 g of Acetylcysteine add 3M hydrochloric acid until the pH of the solution is 2.0.
Add, while stirring continuously, two 200 -mg portions of finely powdered sodium chloride followed, if necessary, by further
25-mg portions of sodium chloride until a precipitate begins to appear. Allow to stand for 15 minutes, filter and dry the
residue at 70° at a pressure not exceeding 0.7 kPa for 2 hours. The infrared absorption spectrum of the residue, Appendix
II A, is concordant with the reference spectrum of acetylcysteine (RS 003). Examine as discs prepared using potassium
bromide.
TESTS
Acidity or alkalinity
pH, 6.5 to 7.5, Appendix V L.
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions. With the exception of
solution (3), the solutions should be prepared immediately before use.
(1) Dilute the injection with the mobile phase to produce a solution containing the equivalent of 0.2% w/v of
Acetylcysteine.
(2) Dissolve 20 mg of L-cysteine (impurity B) and 20 mg of L-cystine (impurity A) in 10 mL of 1M hydrochloric acid, add
40 mg of acetylcysteine BPCRS and immediately dilute to 100 mL with the mobile phase. Dilute 1 volume of the resulting
solution to 20 volumes with the mobile phase.
(3) 0.2% w/v solution of acetylcysteine BPCRS in the mobile phase and store at room temperature for at least 2 hours
before use (generation of N,N′-diacetylcystine).
(4) Dilute 1 volume of solution (2) to 10 volumes with mobile phase.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 5 mm) packed with octadecylsilyl silica gel for chromatography (5 µm)
(LiChrosorb RP18 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 1 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 205 nm.
(f) Inject 20 µL of each solution.
(g) Allow the chromatography to proceed for three times the retention time of acetylcysteine.
MOBILE PHASE
10 volumes of methanol and 90 volumes of a 0.5% w/v solution of ammonium sulfate containing 0.02M sodium
pentanesulfonate. Adjust the pH of the mixture, if necessary, to pH 2.0 using 2M hydrochloric acid.
When the chromatograms are recorded under the prescribed conditions, the relative retentions with reference to
acetylcysteine (retention time about 6 minutes) are: cystine, about 0.6; cysteine, about 0.7; N,N′-diacetylcystine, about 2.2.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (2), the peak-to-valley ratio is at least 2.5, where
Hp is the height above the baseline of the peak due to cysteine and Hv is the height above the baseline of the lowest point
of the curve separating this peak from the peak due to cystine.
LIMITS
In the chromatogram obtained with solution (1):
the area of any peak corresponding to N,N′-diacetylL-cystine (impurity C) is not greater than the area of the peak due to
acetylcysteine in the chromatogram obtained with solution (2) (1%);
the area of any peak corresponding to L-cysteine (impurity B) is not greater than twice the area of the corresponding peak
in the chromatogram obtained with solution (2) (1%);
the area of any peak corresponding to L-cystine (impurity A) is not greater than the area of the corresponding peak in the
chromatogram obtained with solution (2) (0.5%);
the sum of the areas of any other secondary peaks is not greater than the area of the peak due to acetylcysteine in the
chromatogram obtained with solution (2) (1%).
Disregard any peak with an area less than the area of the peak due to acetylcysteine in the chromatogram obtained with
solution (4) (0.1%).
Hydrogen sulfide
Place a quantity of the injection containing the equivalent of 0.4 g of Acetylcysteine in a round-bottomed, three-necked
flask containing 40 mL of water. The flask is fitted with a gas inlet tube which reaches nearly to the bottom of the flask, a
dropping funnel containing hydrochloric acid and an outlet tube leading to a 100 mL graduated flask containing a mixture
of 1 mL of 5M sodium hydroxide and 50 mL of water. Pass through the flask a steady current of nitrogen and add 10 mL of
hydrochloric acid from the dropping funnel. Maintain the current of nitrogen for 30 minutes and then disconnect the
absorption flask. Add to the flask 10 mL of a solution prepared by dissolving 0.1 g of N,N-dimethyl-p-phenylenediamine
dihydrochloride in a mixture of 45 mL of hydrochloric acid and 55 mL of water decolourised with activated charcoal before
use, if necessary, and 5 mL of a 5% w/v solution of iron(III) chloride hexahydrate in 1M hydrochloric acid and allow to stand
for 20 minutes protected from light. Add sufficient water to produce 100 mL and measure the absorbance of the solution,
Appendix II B, at 665 nm using a 4 cm pathlength and using in the reference cell a solution prepared in the same manner
but without the injection being examined.
Prepare a 0.4% w/v solution of sodium sulfide. Standardise this solution in the following manner. To 25 mL of 0.05M iodine
VS add 8 mL of hydrochloric acid and 25 mL of the sodium sulfide solution. Titrate with 0.1M sodium thiosulfate solution VS
using starch solution, added towards the end point, as indicator. Repeat the operation without the sodium sulfide solution.
The concentration of the sodium sulfide solution expressed in parts per million of hydrogen sulfide is the difference
between the titrations multiplied by 68.16. Prepare a solution containing the equivalent of 20 ppm of hydrogen sulfide by
appropriate dilution of the sodium sulfide solution with water.
Repeat the procedure carried out on the injection using 2 mL of the 20 ppm hydrogen sulfide solution in place of the
injection being examined. The absorbance of the solution obtained from the injection is not greater than the absorbance of
the solution obtained from the standard (100 ppm with reference to the content of acetylcysteine).
Bacterial endotoxins
Carry out the test for bacterial endotoxins, Appendix XIV C. If necessary, dilute the injection with water BET to give a
solution containing 10 mg per mL (solution A). The endotoxin limit concentration of solution A is not more than 0.3 IU
per mL.
ASSAY
Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
(1) Dilute the injection with the mobile phase to produce a solution containing the equivalent of 0.2% w/v of
Acetylcysteine.
(2) 0.2% w/v solution of acetylcysteine BPCRS in the mobile phase.
(3) Dissolve 20 mg of L-cystine (impurity A) and 20 mg of L-cysteine (impurity B) in 10 mL of 1M hydrochloric acid and
dilute to 100 mL with the mobile phase. Dilute 1 volume of the resulting solution to 20 volumes with the mobile phase.
CHROMATOGRAPHIC CONDITIONS
The chromatographic conditions described under Related substances may be used.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (3), the peak-to-valley ratio is at least 2.5, where
Hp is the height above the baseline of the peak due to cysteine and Hv is the height above the baseline of the lowest point
of the curve separating this peak from the peak due to cystine.
DETERMINATION OF CONTENT
Calculate the content of C5H9NO3S in the injection using the declared content of C5H9NO3S in acetylcysteine BPCRS.
STORAGE
Acetylcysteine Injection should be protected from light.
LABELLING
The strength is stated in terms of the equivalent amount of acetylcysteine in a suitable dose-volume.
IMPURITIES
The impurities limited by the requirements of this monograph include impurities A, B and C listed under Acetylcysteine.
