Paricalcitol

(par'' i kal' si tol).

C27H44O3

416.64

19-Nor-1-

,25-dihydroxyvitamin D2.
(1

,7E,22E)-19-Nor-9,10-secoergosta-5,7,22-triene-1,3,25-triol.
(7E,22E)-19-Nor-9,10-secoergosta-5,7,22-triene-1

,25-triol

[131918-61-1].

» Paricalcitol contains not less than 97.0 percent and not more than 103.0 percent of C27H44O3, calculated on the dried basis.

[Caution—Handle Paricalcitol with exceptional care because it is very potent. Care should be taken to prevent inhaling particles of Paricalcitol and exposing the skin to it. ]

Packaging and storage— Preserve in tight, light-resistant containers, and store under argon in a freezer.

USP Reference standards

—

USP Paricalcitol RS

USP Paricalcitol Solution RS

Identification—

A: Infrared Absorption

197K

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

Loss on drying (see Thermal Analysis

891

)— Determine the percentage of volatile substances by thermogravimetric analysis on an appropriately calibrated instrument, using about 8 mg of Paricalcitol, accurately weighed. Heat at a rate of 5

per minute between ambient temperature and 150

in an atmosphere of nitrogen at a flow rate of 40 mL per minute. From the thermogram determine the accumulated loss in weight: it loses not more than 2.0% of its weight.

Chromatographic purity— [note—Use low-actinic glassware to prepare solutions of Paricalcitol. ]

Diluent— Prepare a mixture of water and dehydrated alcohol (1:1).

Butylparaben solution— Transfer about 25 mg of butylparaben to a 100-mL volumetric flask, dilute with Diluent to volume, and mix.

Solution A— Use a filtered and degassed mixture of water and acetonitrile (95:5), and add 1 drop of phosphoric acid per L of solution.

Solution B— Use filtered and degassed acetonitrile.

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography

621

Standard solution— Dilute USP Paricalcitol Solution RS in Diluent to a known concentration of about 0.1 µg of paricalcitol per mL.

Control standard solution— Transfer 3.0 mL of the Standard solution to a 10.0-mL volumetric flask, dilute with Diluent to volume, and mix.

Test stock solution— Prepare a solution of Paricalcitol in dehydrated alcohol, having a known concentration of about 200 µg per mL.

Resolution solution— Transfer 1 mL of the Butylparaben solution and 1 mL of the Test stock solution to a 100-mL volumetric flask, dilute with Diluent to volume, and mix. Transfer 1 mL of this solution to a 10-mL volumetric flask, dilute with Diluent to volume, and mix.

Test solution— Prepare a mixture of the Test stock solution and water (1:1).

Chromatographic system (see Chromatography

621

)— The liquid chromatograph is equipped with a 252-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 2 mL per minute. The chromatograph is programmed as follows.

Time (minutes)	Solution A (%)	Solution B (%)	Elution
0–10	100	0	isocratic
10–30	100®47	0®53	linear gradient
30–40	47	53	isocratic
40–45	47®0	53®100	linear gradient
45–50	0	100	isocratic
50–51	0®100	100®0	linear gradient
51–60	100	0	re-equilibration

Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between paricalcitol and butylparaben is not less than 12.0. Chromatograph the Standard solution and the Control standard solution, and record the peak responses as directed for Procedure: the area ratio for the paricalcitol peak from the Standard solution to that from the Control standard solution is between 1.8 and 4.0; and the relative standard deviation for replicate injections of the Standard solution is not more than 10.0%.

Procedure— Separately inject equal volumes (about 100 µL) of the Diluent, the Standard solution, and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses, disregarding any peaks corresponding to those obtained from the Diluent. Calculate the percentage of each impurity in the portion of Paricalcitol taken by the formula:

100(CS / CU)(ri / rS)

in which CS and CU are the concentrations, in µg per mL, of paricalcitol in the Standard solution and the Test solution, respectively; ri is the peak response for each impurity obtained from the Test solution; and rS is the paricalcitol peak response obtained from the Standard solution: not more than 0.1% of any individual impurity is found; and not more than 0.5% of total impurities is found.

Assay— [note—Use low-actinic glassware to prepare solutions of paricalcitol. ]

Mobile phase— Prepare a filtered and degassed mixture of methanol and water (4:1). Make adjustments if necessary (see System Suitability under Chromatography

621

Diluent— Prepare a mixture of methanol and water (1:1).

Standard preparation— Transfer an accurately weighed amount of USP Paricalcitol RS to a suitable volumetric flask, dissolve in a minimum amount of dehydrated alcohol, and dilute with Diluent to volume. Further dilute this solution quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 5.0 µg per mL.

Assay preparation— Transfer an accurately weighed amount of Paricalcitol to a suitable volumetric flask, dissolve in a minimum amount of dehydrated alcohol, and dilute with Diluent to volume. Further dilute this solution quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 5.0 µg per mL.

Chromatographic system (see Chromatography

621

)— The liquid chromatograph is equipped with a 252-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 100 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 percentage of C27H44O3 in the portion of Paricalcitol taken by the formula:

100(CS / CU)(rU / rS)

in which CU and CS are the concentrations, in µg per mL, of paricalcitol in the Assay preparation and the Standard preparation, respectively; and rU and rS are the paricalcitol peak responses obtained from the Assay preparation and the Standard preparation, respectively.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Elena Gonikberg, Ph.D. Principal Scientific Liaison 1-301-816-8251	(SM32010) Monographs - Small Molecules 3
Reference Standards	RS Technical Services 1-301-816-8129 rstech@usp.org

USP35–NF30 Page 4220

Pharmacopeial Forum: Volume No. 33(2) Page 252