Alprostadil
(al pros' ta dil).
Click to View Image
C20H34O5 354.48
Prost-13-en-1-oic acid, 11,15-dihydroxy-9-oxo-, (11,13E,15S)-.
(1R,2R,3R)-3-Hydroxy-2-[(E)-(3S)-3-hydroxy-1-octenyl]-5-oxocyclopentane heptanoic acid [745-65-3].
» Alprostadil contains not less than 95.0 percent and not more than 105.0 percent of C20H34O5, calculated on the anhydrous basis.
[Caution—Great care should be taken to prevent inhaling particles of Alprostadil and exposing the skin to it. ]
Packaging and storage— Preserve in tight containers, and store in a refrigerator.
USP Reference standards 11
USP Alprostadil RS Click to View Structure
USP Prostaglandin A1 RS Click to View Structure
USP Prostaglandin B1 RS Click to View Structure
    C20H32O4    336.47
Water, Method I 921: not more than 0.5%, using 0.5 g.
Residue on ignition 281: not more than 0.5%, using 0.3 g.
Limit of chromium—
Standard solution— Dissolve an accurately weighed quantity of chromium trichloride in 0.05 M nitric acid, and dilute, stepwise if necessary, with 0.05 M nitric acid to obtain a solution having a known concentration of about 3.04 µg per mL. Transfer 2 mL of this solution to a 100-mL volumetric flask, dilute with alcohol to volume, and mix. This solution contains 20 ng of chromium per mL.
Test solution— Transfer about 10 mg of Alprostadil, accurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with alcohol to volume, and mix.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into a suitable graphite furnace atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering 851), equipped with a chromium hollow-cathode lamp, with a drying temperature of 100, an ashing temperature of 1000, and an atomization temperature of 2700. Use alcohol as the blank. Concomitantly determine the absorbances at the chromium emission line at 357.9 nm, and calculate the percentage of chromium (Cr) in the portion of Alprostadil taken by the formula:
100(CS /CA)(AU /AS)
in which CS is the concentration, in mg per mL, of chromium in the Standard solution; CA is the concentration, in mg per mL, of Alprostadil in the Test solution; and AU and AS are the absorbances obtained from the Test solution and Standard solution, respectively: not more than 0.002% is found.
Limit of rhodium—
Standard solution— Dissolve an accurately weighed quantity of rhodium chloride hydrate in 1.2 M hydrochloric acid, and dilute, stepwise if necessary, with 1.2 M hydrochloric acid to obtain a solution having a known concentration of 100 µg of rhodium per mL. Transfer 5 mL of this solution to a 100-mL volumetric flask, dilute with alcohol to volume, and mix. Transfer 2 mL of this solution to a 200-mL volumetric flask, dilute with alcohol to volume, and mix. This solution contains 50 ng of rhodium per mL.
Test solution— Transfer about 20 mg of Alprostadil, acccurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with alcohol to volume, and mix.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into a suitable graphite furnace atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering 851), equipped with a rhodium hollow-cathode lamp, with a drying temperature of 100, an ashing temperature of 1000, and an atomization temperature of 2800. Use alcohol as the blank. Concomitantly determine the absorbances at the rhodium emission line at 343.5 nm, and calculate the percentage of rhodium (Rh) in the portion of Alprostadil taken by the formula:
100(CS /CA)(AU /AS)
in which CS is the concentration, in mg per mL, of rhodium in the Standard solution; CA is the concentration, in mg per mL, of Alprostadil in the Test solution; and AU and AS are the absorbances obtained from the Test solution and the Standard solution, respectively: not more than 0.002% is found.
Limit of foreign prostaglandins—
test 1
[note—Use freshly prepared solutions. Measure the peak responses at the following wavelengths: prostaglandin A1 at 224 nm; prostaglandin B1 at 280 nm; and all other foreign prostaglandin impurities at 200 nm. ]
Mobile phase— Proceed as directed in the Assay.
Standard solution— Dissolve accurately weighed quantities of USP Alprostadil RS, USP Prostaglandin A1 RS, and USP Prostaglandin B1 RS in a mixture of methanol and water (9:1), and dilute quantitatively, and stepwise if necessary, with a mixture of methanol and water (9:1) to obtain a solution having known concentrations of about 6 µg per mL, 15 µg per mL, and 6 µg per mL, respectively.
Test solution— Dissolve about 15 mg of Alprostadil, accurately weighed, in 5 mL of a mixture of methanol and water (9:1), and mix.
Chromatographic system— Proceed as directed in the Assay. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the resolution between prostaglandin A1 and alprostadil is not less than 7.5, and the relative standard deviation from the peaks at their respective wavelength for replicate injections is not more than 4.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses at 200 nm, 224 nm, and 280 nm. Calculate the percentage of prostaglandin A1 and prostaglandin B1 in the portion of Alprostadil taken by the formula:
500(CS / W)(rI / rS)
in which CS is the concentration, in mg per mL, of USP Prostaglandin A1 RS or USP Prostaglandin B1 RS in the Standard solution; W is the weight, in mg, of Alprostadil taken for the Test solution; ri is the peak response for prostaglandin A1 or prostaglandin B1 obtained from the Test solution; and rS is the peak response of prostaglandin A1 or prostaglandin B1 obtained from the Standard solution: not more than 1.5% of prostaglandin A1 is found; and not more than 0.1% of prostaglandin B1 is found. Calculate the percentage of each impurity occurring at 200 nm and eluting before prostaglandin A1 in the portion of Alprostadil taken by the formula:
500(CS / W)(rI / rS)
in which CS is the concentration, in mg per mL, of USP Alprostadil RS in the Standard solution; ri is the peak response for each impurity obtained from the Test solution; rS is the peak response for alprostadil obtained from the Standard solution; and the other terms are as defined herein: not more than 0.9% of any foreign prostaglandin impurity is found. Calculate the percentage of any impurity having a relative retention time of 0.6, relative to the prostaglandin A1 peak detected at 224 nm, in the portion of Alprostadil taken by the formula:
500(CS / W)(rI / rS)
in which CS is the concentration, in mg per mL, of USP Prostaglandin A1 RS in the Standard solution; rI is the peak response for any impurity having a relative retention time of 0.6, relative to the prostaglandin A1 peak, obtained from the Test solution; rS is the peak response of prostaglandin A1 obtained from the Standard solution; and the other terms are as defined herein: not more than 0.9% of any impurity having a relative retention time of 0.6, relative to the prostaglandin A1 peak, is found.
test 2—
Mobile phase— Prepare a filtered and degassed mixture of methanol, acetonitrile, and 0.02 M monobasic potassium phosphate (2:1:1), and adjust with phosphoric acid to a pH of 3. Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard solution— Dissolve an accurately weighed quantity of USP Alprostadil RS in a mixture of acetonitrile and water (1:1) to obtain a solution having a known concentration of about 10 µg per mL.
Test solution— Dissolve about 25 mg of Alprostadil, accurately weighed, in 5 mL of a mixture of acetonitrile and water (1:1), using ultrasound if necessary.
Identification solution— Use the Standard solution under Test 1.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a photodiode array detector or equivalent capable of detecting UV wavelengths between 200 nm and 300 nm and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1.2 mL per minute. Chromatograph the Identification solution as directed for Procedure: the relative retention times for prostaglandin A1 and alprostadil are about 1.2 and 1.0, respectively; the resolution between prostaglandin A1 and alprostadil is not less than 4.0. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the relative standard deviation determined from the main peak for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses at 200 nm, 224 nm, and 280 nm. Calculate the percentage of each impurity occurring at 200 nm and eluting after prostaglandin A1, excluding prostaglandin B1, in the portion of Alprostadil taken by the formula:
500(CS / W)(rI / rS)
in which CS is the concentration, in mg per mL, of USP Alprostadil RS in the Standard solution; W is the weight, in mg, of Alprostadil taken for the Test solution; rI is the peak response for each impurity obtained from the Test solution; and rS is the peak response for alprostadil obtained from the Standard solution: the sum of the peaks having relative retention times of 2.0 and 2.3 is not more than 0.6%; not more than 0.9% of any other foreign prostaglandin impurity is found; and not more than 2.0% of total impurities is found, the results for Test 1 and Test 2 being added.
Assay—
[note—Use freshly prepared solutions. ]
Mobile phase— Prepare a filtered and degassed mixture of methanol, 0.1 M monobasic potassium phosphate and acetonitrile (2:2:1), and adjust with phosphoric acid to a pH of 3.0. Make adjustments if necessary (see System Suitability under Chromatography 621).
Internal standard solution— Dissolve an accurately weighed quantity of ethylparaben in a mixture of methanol and water (9:1), and dilute quantitatively, and stepwise if necessary, with a mixture of methanol and water (9:1) to obtain a solution having a concentration of about 0.05 mg per mL.
Standard preparation— Dissolve an accurately weighed quantity of USP Alprostadil RS in a mixture of methanol and water (9:1), and dilute quantitatively, and stepwise if necessary, with a mixture of methanol and water (9:1) to obtain a solution having a known concentration of about 0.3 mg per mL. To 2.0 mL of this solution, add 1.0 mL of Internal standard solution, and mix.
System suitability solution— Dilute an accurately measured amount of USP Prostaglandin A1 RS with Standard preparation to obtain a solution having a concentration of 4.5 µg of prostaglandin A1 per mL. To 2.0 mL of this solution, add 1.0 mL of Internal standard solution, and mix.
Assay preparation— Transfer about 7.5 mg of Alprostadil, accurately weighed, to a 25-mL volumetric flask, dissolve in and dilute with a mixture of methanol and water (9:1) to volume, and mix. To 2.0 mL of this solution, add 1.0 mL of Internal standard solution, and mix.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a photodiode array detector or equivalent capable of detecting UV wavelengths between 200 nm and 300 nm and a 4.6-mm × 25-cm column that contains packing L1. The column temperature is maintained at 40. The flow rate is about 1 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between prostaglandin A1 and alprostadil is not less than 7.5, and between prostaglandin A1 and ethylparaben is not less than 2.0; and the relative standard deviation determined from the peak area ratio of alprostadil to ethylparaben 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 at 200 nm, and measure the areas for the major peaks. Calculate the quantity, in mg, of C20H34O5 in the portion of Alprostadil taken by the formula:
25C(RU /RS)
in which C is the concentration, in mg per mL, of USP Alprostadil RS in the Standard preparation; and RU and RS are the peak area ratios of alprostadil to ethylparaben obtained from the Assay preparation and the Standard preparation, respectively.
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