Timolol Maleate

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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C₁₃H₂₄N₄O₃S · C₄H₄O₄        432.49

2-Propanol, 1-[(1,1-dimethylethyl)amino]-3-[[4-(4-morpholinyl)-1,2,5-thiadiazol-3-yl)oxy]-, (S)-, (Z)-2-butenedioate (1:1) (salt);

(-)-1-(tert-Butylamino)-3-[(4-morpholino-1,2,5-thiadiazol-3-yl)oxy]-2-propanol maleate (1:1) (salt) CAS RN^®: 26921-17-5; UNII: P8Y54F701R.

1 DEFINITION

Timolol Maleate contains NLT 98.0% and NMT 102.0% of timolol maleate (CHNOS CHO), calculated on the dried basis.

2 IDENTIFICATION

Change to read:

A. ^▲SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197M or 197A _{▲(CN 1-May-2020)}

B. The retention time of the timolol peak of the Sample solution corresponds to that of the System suitability solution, as obtained in the Enantiomeric Purity test.

3 ASSAY

PROCEDURE

Solution A: Dilute 0.5 mL of trifluoroacetic acid with water to 1 L.

Solution B: Dilute 0.5 mL of trifluoroacetic acid with acetonitrile to 1 L.

Mobile phase: See Table 1.

Table 1

Diluent: Methanol and water (60:40)

System suitability solution: 100 µg/mL of USP Timolol Maleate RS and 10 µg/mL of USP Timolol Related Compound D RS in Diluent

Standard solution: 100 µg/mL of USP Timolol Maleate RS in Diluent

Sample solution: 100 µg/mL of Timolol Maleate in Diluent

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 295 nm

Column: 2.1-mm x 10-cm; 2.6-µm packing L1

Autosampler temperature: 4°

Flow rate: 0.4 mL/min

Injection volume: 2.5 µL

System suitability

Samples: System suitability solution and Standard solution

Suitability requirements

Resolution: NLT 2 between timolol and timolol related compound D, System suitability solution

Tailing factor: NMT 2.0, Standard solution

Relative standard deviation: NMT 0.73%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of timolol maleate (C₁₃H₂₄N₄O₃S · C₄H₄O₄) in the portion of Timolol Maleate taken:

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

r_U = peak response of timolol from the Sample solution

r_S = peak response of timolol from the Standard solution

C_S = concentration of USP Timolol Maleate RS in the Standard solution (µg/mL)

C_U = concentration of Timolol Maleate in the Sample solution (ug/mL)

Acceptance criteria: 98.0%-102.0% on the dried basis

4 IMPURITIES

4.1 RESIDUE ON IGNITION (281)

NMT 0.1%

Change to read:

4.2 ORGANIC IMPURITIES

Solution A, Solution B, Mobile phase, Diluent, and Chromatographic system: Proceed as directed in the Assay.

^▲Sensitivity solution: 0.5 µg/mL of USP Timolol Maleate RS in Diluent _{▲(USP 1-Dec-2019)}

System suitability solution: 100 µg/mL each of USP Timolol Maleate RS. USP Timolol Related Compound B RS, USP Timolol Related Compound C RS, USP Timolol Related Compound D RS, USP Timolol Related Compound E RS, and USP Timolol Related Compound F. RS in Diluent. [NOTE-Prepare fresh and analyze immediately as USP Timolol Related Compound E RS degrades rapidly.]

Standard solution: 1 µg/mL of USP Timolol Maleate RS and 4 µg/mL each of USP Timolol Related Compound B RS, USP Timolol Related Compound C RS, USP Timolol Related Compound D RS, USP Timolol Related Compound E RS, and USP Timolol Related Compound F. RS in Diluent. Sonicate if needed for 0.5 min.

Sample solution: 1 mg/mL of Timolol Maleate in Diluent

System suitability

Samples: ^▲Sensitivity solution _{▲(USP 1-Dec-2019)} System suitability solution, and Standard solution

Suitability requirements

Resolution: NLT 2.0 between timolol and timolol related compound D, System suitability solution

Relative standard deviation: NMT 4.0% for timolol, Standard solution

^▲Signal-to-noise ratio: NLT 10 for timolol, Sensitivity solution _{▲(USP 1-Dec-2019)}

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of timolol maleate ester (free base of timolol related compound E) in the portion of Timolol Maleate taken:

                          Result = (r_U/r_S) × (C_S/C_U) x (M_r1/M_r2) ×100

r_U = peak response of timolol maleate ester from the Sample solution 

r_S = peak response of timolol maleate ester from the Standard solution

C_S = concentration of USP Timolol Related Compound E RS in the Standard solution (µg/mL)

C_U = concentration of Timolol Maleate in the Sample solution (µg/mL)

M_r1 = molecular weight of timolol maleate ester, 414.48

M_r2 = molecular weight of timolol related compound E, 530.55

Calculate the percentage of timolol bisthiadiazol analog (free base of timolol related compound C) in the portion of Timolol Maleate taken:

                          Result = (r_U/r_S) × (C_S/C_U) x (M_r1/M_r2) ×100

r_U = peak response of timolol bisthiadiazol from the Sample solution

r_S = peak response of timolol bisthiadiazol from the Standard solution

C_S = concentration of USP Timolol Related Compound C RS in the Standard solution (µg/mL)

C_U = concentration of Timolol Maleate in the Sample solution (µg/mL)

M_r1 = molecular weight of timolol bisthiadiazol, 485.62

M_r2 = molecular weight of timolol related compound C, 601.69 _{▲(USP 1-Dec-2019)}

Calculate the percentage of ^▲timolol related compound B, D, or F _{▲(USP 1-Dec-2019)} in the portion of Timolol Maleate taken:

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

r_U = peak response of ^▲timolol related compound B, D, or F _{▲(USP 1-Dec-2019)} from the Sample solution

r_S = peak response of ^▲timolol related compound B, D, or F _{▲(USP 1-Dec-2019)} from the Standard solution

C_S = concentration of ^▲USP Timolol Related Compound B RS, USP Timolol Related Compound D RS, or USP Timolol Related Compound F RS _{▲(USP 1-Dec-2019)} in the Standard solution (µg/mL)

C_U = concentration of Timolol Maleate in the Sample solution (µg/mL)

Calculate the percentage of any individual unspecified impurity in the portion of Timolol Maleate taken:

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

r_U = peak response of any individual unspecified impurity from the Sample solution 

r_S = peak response of timolol from the Standard solution

C_S = concentration of USP Timolol Maleate RS in the Standard solution (µg/mL)

C_U = concentration of Timolol Maleate in the Sample solution (µg/mL)

Acceptance criteria: See Table 2. ^▲The reporting threshold is 0.05% _{▲(USP 1-Dec-2019)}

Table 2

^▲a (S)-3-(tert-Butylamino)-1-(4-morpholino-1,2,5-thiadiazol-3-yloxy)propan-2-yl hydrogen maleate.

^b N-(tert-Butyl)-2,3-bis(4-morpholino-1,2,5-thiadiazol-3-yloxy)propan-1-amine. _{▲(USP 1-Dec-2019)}

Change to read:

4.3 ENANTIOMERIC PURITY

Prepare all solutions in low-actinic glassware protected from light.

Mobile phase: Diethylamine, 2-propanol, and hexane (2:40:960)

Diluent: Methylene chloride and 2-propanol (25:75)

System suitability solution: 0.03 mg/mL each of USP Timolol Maleate RS and USP Timolol Related Compound A RS in Diluent

Standard solution: 0.03 mg/mL of USP USP Timolol Related Compound A RS in Diluent

Sample solution: 3 mg/mL of Timolol Maleate in Diluent

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 297 nm

Column: 4.6-mm x 25-cm; 5-µm packing L40

Flow rate: 1 mL/min

Injection volume: 5 µL

System suitability

Samples: System suitability solution ^▲and Standard solution _{▲(USP 1-Dec-2019)}

Suitability requirements

Resolution: NLT 4.0 between the timolol related compound A and timolol peaks, System suitability solution

Relative standard deviation: NMT 1.5% for ^▲the timolol related compound A peak, Standard solution _{▲(USP 1-Dec-2019)}

Signal-to-noise ratio: NLT 10 for the timolol related compound A peak, ^▲Standard solution _{▲(USP 1-Dec-2019)}

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of timolol related compound A in the portion of Timolol Maleate taken:

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

r_U = peak response of timolol related compound A from the Sample solution

r_S = peak response of timolol related compound A from the Standard solution

C_S = concentration of USP Timolol Related Compound A RS in the Standard solution (mg/mL)

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

Acceptance criteria: NMT 1.0%

5 SPECIFIC TESTS

5.1 pH (791).

Sample solution: 20 mg/mL of Timolol Maleate in water

Acceptance criteria: 3.8-4.3

5.2 LOSS ON DRYING (731)

Analysis: Dry under vacuum at 100 to constant weight.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Change to read:

PACKAGING AND STORAGE: Preserve in well-closed containers, ^▲protected from light _{▲(USP 1-Dec-2019)}

USP REFERENCE STANDARDS (11)

USP Timolol Maleate RS

USP Timolol Related Compound A RS

(R)-1-(tert-Butylamino)-3-(4-morpholino-1,2,5-thiadiazol-3-yloxy)propan-2-ol maleate.

C₁₃H₂₄N₄O₃S · C₄H₄O₄       432.49

USP Timolol Related Compound B RS

3-(tert-Butylamino)-2-(4-morpholino-1,2,5-thiadiazol-3-yloxy)propan-1-ol.

C₁₃H₂₄N₄O₃S              316.42

USP Timolol Related Compound C RS

N-(tert-Butyl)-2,3-bis(4-morpholino-1,2,5-thiadiazol-3-yloxy)propan-1-amine maleate.

C₁₉H₃₁N₇O₄S₂ · C₄H₄O₄            601.69

USP Timolol Related Compound D. RS

4-Morpholino-1,2,5-thiadiazol-3-ol.

C₆H₉N₃O₂S                187.22

USP Timolol Related Compound ERS

( S, Z)-4-((1-(tert-Butylamino)-3-[(4-morpholino-1,2,5-thiadiazol-3-yl)oxy]propan-2-yl)oxy)-4-oxobut-2-enoic acid maleate salt (1:1).

C₁₇H₂₆N₄O₆S · C₄H₄O₄            530.55

USP Timolol Related Compound FRS

3-Chloro-4-morpholino-1,2,5-thiadiazol.

C₆H₈CIN₃OS              205.67