Pimecrolimus

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₄₃H₆₈ClNO₁₁           810.46

15,19-Epoxy-3H-pyrido[2,1-c][1,4]oxaazacyclotricosine-1,7,20,21(4H,23H)-tetrone, 3-[(1E)-2-[(1R,3R,4S)-4-chloro-3-methoxycyclohexyl]-1- methylethenyl]-8-ethyl-5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-dihydroxy-14,16-dimethoxy-4,10,12,18-tetramethyl-, (3S,4R,5S,8R,9E,12S,14S,15R,16S,18R,19R,26aS)-;

(3S,4R,5S,8R,9E,12S,14S,15R,16S,18R,19R,26aS)-3-[(E)-2-[(1R,3R,4S)-4-Chloro-3-methoxycyclohexyl]-1-methylvinyl]-8-ethyl 5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-epoxy-3H-pyrido[2,1-c][1,4]oxaazacyclotricosine-1,7,20,21(4H,23H)- tetrone CAS RN®: 137071-32-0; UNII: 7KYV510875.

1 DEFINITION

Pimecrolimus contains NLT 98.0% and NMT 102.0% of pimecrolimus (C₄₃H₆₈ClNO₁₁), calculated on the anhydrous and solvent-free basis.

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A or 197K

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

Procedure

[Note—Protect solutions containing pimecrolimus from light and store at 5°. Dissolve quickly with minimum sonication.] Solution A: 0.1% of phosphoric acid in water

Solution B: 0.1% of phosphoric acid in methanol

Mobile phase: Solution A and Solution B (29:71)

Diluent: 0.1% of formic acid in acetonitrile

Standard solution: 0.5 mg/mL of USP Pimecrolimus RS in Diluent

Sample solution: 0.5 mg/mL of Pimecrolimus in Diluent

3.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm × 15-cm; 2.7-µm packing L1

Temperatures

Autosampler: 5°

Column: 60°

Flow rate: 1 mL/min

Injection volume: 10 µL

Run time: NLT 1.8 times the retention time of pimecrolimus

System suitability

Sample: Standard solution

[Note—The relative retention times for pimecrolimus tautomer I and pimecrolimus tautomer II are 0.89 and 0.55, respectively.] Suitability requirements

Tailing factor: 0.8–1.5 for pimecrolimus

Relative standard deviation: NMT 0.73% for pimecrolimus

3.2 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of pimecrolimus (C₄₃H₆₈ClNO₁₁) in the portion of Pimecrolimus taken:

Result = (r_U /r_S) × (C /C_U ) × 100

r_U = sum of the peak response of pimecrolimus, pimecrolimus tautomer I (if present), and pimecrolimus tautomer II (if present) from the Sample solution

r_S = sum of the peak response of pimecrolimus, pimecrolimus tautomer I (if present), and pimecrolimus tautomer II (if present) from the Standard solution

C_S = concentration of USP Pimecrolimus RS in the Standard solution (mg/mL) 

C_U = concentration of Pimecrolimus in the Sample solution (mg/mL) 

Acceptance criteria: 98.0%–102.0% on the anhydrous and solvent-free basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Organic Impurities

[Note—Protect solutions containing pimecrolimus from light and store between 2° and 8°. Avoid sonication while preparing.] Solution A, Solution B, and Diluent: Prepare as directed in the Assay.

Mobile phase: See Table 1.

Table 1

System suitability solution: 6 mg/mL of USP Pimecrolimus System Suitability Mixture RS in Diluent

Standard solution: 0.006 mg/mL of USP Pimecrolimus RS in Diluent

Sample solution: 6 mg/mL of Pimecrolimus in Diluent

4.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm × 15-cm; 2.7-µm packing L1

Temperatures

Autosampler: 5°

Column: 60°

Flow rate: 1 mL/min

Injection volume: 10 µL

4.2 System suitability

Samples: System suitability solution and Standard solution

[Note—The relative retention times in Table 2 are provided as information that could aid in peak assignment.]

Table 2

^a (3S,4R,5S,8R,9E,12S,14S,15R,16S,18R,19R,26aS)-8-Ethyl-5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-dihydroxy-3- [(1E)-2-[(1R,3R,4R)-4-hydroxy-3-methoxycyclohexyl]-1-methylethenyl]-14,16-dimethoxy-4,10,12,18-tetramethyl-15,19-epoxy-3H-pyrido[2,1- c][1,4]oxaazacyclotricosine-1,7,20,21(4H,23H)-tetrone.

^b (3S,4R,5S,8R,12S,14S,15R,16S,18R,19S,26aS,E)-3-{(E)-1-[(1R,3R,4S)-4-Chloro-3-methoxycyclohexyl]prop-1-en-2-yl}-8-ethyl-5,19-dihydroxy 14,16-dimethoxy-4,10,12,18-tetramethyl-5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-3H-15,19-epoxypyrido[2,1-c] [1]oxa[4]azacyclotricosine-1,7,20,21(4H,23H)-tetraone.

^c (3S,4R,5S,8R,9E,12S,14S,15R,16S,18R,19R,26aS)- 3-[(1E)-2-[(1R,3R,4S)-4-chloro-3-methoxycyclohexyl]-1-methylethenyl]-5,6,8,11,12,13,14, 15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-dihydroxy-14,16-dimethoxy-4,8,10,12,18-pentamethyl-15,19-epoxy-3H-pyrido[2,1-c] [1,4]oxaazacyclotricosine-1,7,20,21(4H,23H)-tetrone.

^d (3S,4R,5S,8R,12S,14S,15R,16S,18R,26aS,E)-3-{(E)-1-[(1R,3R,4S)-4-chloro-3-methoxycyclohexyl]prop-1-en-2-yl}-8-ethyl-5,15,20,20- tetrahydroxy-14,16-dimethoxy-4,10,12,18-tetramethyl-3,4,5,6,11,12,13,14,15,16,17,18,24,25,26,26a-hexadecahydro-7H-pyrido[2,1-c] [1]oxa[4]azacyclotricosine-1,7,19,21(8H,20H,23H)-tetraone.

Suitability requirements

Resolution: NLT 2.5 between pimecrolimus and pimecrolimus triene analog, System suitability solution

Relative standard deviation: NMT 5.0% for pimecrolimus, Standard solution

5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of any impurity in the portion of Pimecrolimus taken:

Result = (r_U /r_S) × (C_S /C_U ) × 100

r_U = peak response of any impurity from the Sample solution

r_S = sum of the peak response of pimecrolimus, pimecrolimus tautomer I (if present), and pimecrolimus tautomer II (if present) from the Standard solution

C_S = concentration of USP Pimecrolimus RS in the Standard solution (mg/mL)

C_U = concentration of Pimecrolimus in the Sample solution (mg/mL)

Acceptance criteria: See Table 3.

Table 3

a Excludes pimecrolimus tautomer I and pimecrolimus tautomer II.

6 SPECIFIC TESTS

Water Determination 〈921〉, Method I, Method Ia: NMT 0.5%

Optical Rotation 〈781S〉, Procedures, Specific Rotation

Sample solution: 5 mg/mL of Pimecrolimus in chloroform

Acceptance criteria: −45° to −55° at 20°, calculated on the anhydrous and solvent-free basis

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers. Store between 2° and 8°.

USP Reference Standards 〈11〉

USP Pimecrolimus RS

USP Pimecrolimus System Suitability Mixture RS

Contains a mixture of the following 2 compounds.

Pimecrolimus.

Pimecrolimus triene analog: [3S-[3R[E(1S,5S)],4S,5R,8S,9E,12R,14R,15S,16R,18S,19S,26aR]]-8-Ethyl

5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-dihydroxy-14,16-dimethoxy-3-[2-(5-methoxy-3-cyclohexen-1-yl)-1- methylethenyl]-4,10,12,18-tetramethyl-15,19-Epoxy-3H-pyrido[2,1-c][1,4]oxaazacyclotricosine-1,7,20,21(4H,23H)-tetrone.

C₄₃H₆₇NO₁₁          774.01

Other known impurities may also be present, such as

Desmethylpimecrolimus: (3S,4R,5S,8R,9E,12S,14S,15R,16S,18R,19R,26aS)-3-[(1E)-2-[(1R,3R,4S)-4-Chloro-3-methoxycyclohexyl]-1-methylethenyl]- 5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro-5,19-dihydroxy-14,16-dimethoxy-4,8,10,12,18-pentamethyl-15,19-epoxy-3H pyrido[2,1-c][1,4]oxaazacyclotricosine-1,7,20,21(4H,23H)-tetrone.

C₄₂H₆₆ClNO₁₁      796.44 (USP 1-Aug-2024)