Ritonavir Tablets

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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1 DEFINITION 

Ritonavir Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of ritonavir (C₃₇H₄₈N₆O₅S₂). 

2 IDENTIFICATION 

A. 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 

Buffer: 4.1 g/L of monobasic potassium phosphate 

Solution A: Acetonitrile and Buffer (50:50) 

Solution B: Acetonitrile, butyl alcohol, water, and Buffer (65:15:10:10) 

Mobile phase: Acetonitrile, methanol, tetrahydrofuran (stabilizer-free), and Buffer (17.5:10:10:62.5). Filter the required solutions individually before use. 

Standard solution: 0.1 mg/mL of USP Ritonavir RS in Solution A 

Sample stock solution: Nominally 1 mg/mL of ritonavir prepared as follows. Transfer Tablets (NLT 5) equivalent to 500 mg of ritonavir into a 500-mL volumetric flask. Fill the flask half full with Solution B, and mechanically shake for at least 60 min or until the Tablets have visually disintegrated. Dilute with Solution B to volume, and stir for 30 min. Transfer a sufficient quantity of this solution to a centrifuge tube, and centrifuge for about 15 min. Use the supernatant to prepare the Sample solution. 

Sample solution: Nominally 0.1 mg/mL of ritonavir in Solution A from the supernatant of Sample stock solution 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 215 nm 

Column: 4.6-mm × 15-cm; 5-µm packing L7 

Column temperature: 40° 

Flow rate: 1.5 mL/min 

Injection volume: 50 µL 

System suitability 

Sample: Standard solution 

Suitability requirements 

Capacity factor: 15–24 

Tailing factor: 0.8–1.2 

Relative standard deviation: NMT 2.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of ritonavir (C₃₇H₄₈N₆O₅S₂) in the portion of Tablets taken: 

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = peak response from the Sample solution 

r_S = peak response from the Standard solution 

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

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

Acceptance criteria: 90.0%–110.0% 

4 PERFORMANCE TESTS 

Dissolution 〈711〉 

Medium: 0.06 M polyoxyethylene 10 lauryl ether; 900 mL 

Apparatus 2: 75 rpm 

Time: 120 min 

Buffer: 4.1 g/L of monobasic potassium phosphate 

Mobile phase: Acetonitrile and Buffer (55:45). Adjust with phosphoric acid to a pH of 4.0 ± 0.1. Standard stock solution: 1.11 mg/mL of USP Ritonavir RS in methanol 

Standard working solution: 111 µg/mL of USP Ritonavir RS in Medium from Standard stock solution Sample solution: Pass a portion of the solution under test through a suitable filter. Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 215 nm 

Column: 4.6-mm × 15-cm; 5-µm packing L1 

Flow rate: 1.5 mL/min 

Injection volume: 25 µL 

System suitability 

Sample: Standard solution 

Suitability requirements Tailing factor: 0.9–1.5 

Capacity factor: Greater than 3.5 

Relative standard deviation: NMT 2.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of ritonavir (C₃₇H₄₈N₆O₅S₂) dissolved: 

Result = (r_U/r_S) × (C_S/L) × V × 100 

r_U = peak response from the Sample solution 

r_S = peak response from the Standard solution 

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

L = label claim for ritonavir (mg/Tablet) 

V = volume of Medium, 900 mL 

Tolerances: NLT 75% (Q) of the labeled amount of ritonavir (C₃₇H₄₈N₆O₅S₂) is dissolved. 

Uniformity of Dosage Units 〈905〉: Meet the requirements 

5 IMPURITIES 

Organic Impurities 

Ritonavir is alkali sensitive. All glassware should be pre-rinsed with distilled water before use to remove residual detergent contamination. Buffer A: 4.1 g/L of monobasic potassium phosphate 

Buffer B: 3.8 g/L of monobasic potassium phosphate and 0.25 g/L of dibasic potassium phosphate 

Solution A: Acetonitrile and Buffer A (50:50) 

Solution B: Acetonitrile, butyl alcohol, water, and Buffer A (65:15:10:10) 

Solution C: Acetonitrile, butyl alcohol, and Buffer A (15:5:80) 

Mobile phase: Acetonitrile, butyl alcohol, tetrahydrofuran (stabilizer-free), and Buffer B (18:5:8:69) adjusted with 1 M phosphoric acid or 1 M potassium hydroxide, if necessary, to an apparent pH of 6.3 ± 0.1 

Cleaning solution: Acetonitrile, butyl alcohol, tetrahydrofuran (stabilizer-free), and Buffer A (30:8:13:49) 

Standard stock solution: 0.05 mg/mL of USP Ritonavir RS in Solution A 

Standard solution: 2.5 µg/mL of USP Ritonavir RS in Solution C from Standard stock solution 

System suitability stock solution: 1 mg/mL of USP Ritonavir Related Compounds Mixture RS in Solution B

System suitability solution: 0.5 mg/mL of USP Ritonavir Related Compounds Mixture RS in Solution C from System suitability stock solution Sample stock solution: Nominally 1 mg/mL prepared as follows. Transfer Tablets (NLT 5) equivalent to 500 mg of ritonavir into a 500-mL volumetric flask. Fill the flask half full with Solution B, and mechanically shake for at least 60 min or until the Tablets have visually disintegrated. Dilute with Solution B to volume, and stir for 30 min. Transfer a sufficient quantity of this solution to a centrifuge tube, and centrifuge for 15 min. Use the supernatant to prepare the Sample solution. 

Sample solution: Nominally 0.5 mg/mL of ritonavir in Solution C from the supernatant of Sample stock solution 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 240 nm 

Column: 4.6-mm × 15-cm; 3-µm packing L26. Wash the column after each injection of the Sample solution with Cleaning solution for about 26 min, and equilibrate with Mobile phase for about 30 min. Store in Cleaning solution after the analysis is completed. Column temperature: 60° 

Flow rate: 1 mL/min 

Injection volume: 50 µL 

Run time: 2.4 times the retention time of ritonavir 

System suitability 

Samples: Standard solution and System suitability solution 

See Table 1 for relative retention values. Disregard all peaks occurring before the N-deacylvaline ritonavir peak. 

Suitability requirements 

Resolution: Greater than 0.7 between the hydroxyritonavir and hydantoin aminoalcohol peaks, System suitability solution Capacity factor: Greater than 10.8, Standard solution 

Tailing factor: 0.8–1.2, Standard solution 

Relative standard deviation: NMT 5.0%, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of each impurity in the portion of Tablets taken: 

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × 100 

r_U = peak response of each impurity from the Sample solution 

r_S = peak response of ritonavir from the Standard solution 

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

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

F = relative response factor (See Table 1) 

Acceptance criteria: See Table 1. Disregard peaks less than 0.05%. 

Table 1 

aThiazol-5-ylmethyl (2S,3S,5S)-5-[(S)-2-amino-3-methylbutanamido]-3-hydroxy-1,6-diphenylhexan-2-ylcarbamate.

b Degradation product. 

c Thiazol-5-ylmethyl (2S,3S,5S)-5-acetamido-3-hydroxy-1,6-diphenylhexan-2-ylcarbamate. 

d Process impurity included in this table for peak identication only. This impurity is controlled in the drug substance. It is not to be reported for the drug product nor included in the total impurities. 

e Bis(thiazol-5-ylmethyl) (2S,3S,5S)-3-hydroxy-1,6-diphenylhexane-2,5-diyldicarbamate. (Two peaks may be detected with a relative retention value of 0.24. The rst peak is considered as an unknown impurity and the second as 2,5-thiazolylmethyldicarbamate.) f Thiazol-5-ylmethyl (2S,3S,5S)-3-hydroxy-5-[(S)-2-(3-{[2-(2-hydroxypropan-2-yl)thiazol-4-yl]methyl}-3-methylureido)-3- methylbutanamido]-1,6-diphenylhexan-2-ylcarbamate. 

g Thiazol-5-ylmethyl (2S,3S,5S)-3-hydroxy-5-[(S)-4-isopropyl-2,5-dioxoimidazolidin-1-yl]-1,6-diphenylhexan-2-ylcarbamate. 

h Thiazol-5-ylmethyl (2S,3S,5S)-5-[(S)-2-(3-{[2-(2-hydroperoxypropan-2-yl)thiazol-4-yl]methyl}-3-methylureido)-3-methylbutanamido]-3- hydroxy-1,6-diphenylhexan-2-ylcarbamate. 

i (4S,5S)-Thiazol-5-ylmethyl 4-benzyl-5-{(S)-2-[(S)-4-isopropyl-2,5-dioxoimidazolidin-1-yl]-3-phenylpropyl}-2-oxooxazolidine-3-carboxylate. j Thiazol-5-ylmethyl (2S,3S,5S)-5-[(S)-2-{3-[(2-ethylthiazol-4-yl)methyl]-3-methylureido}-3-methylbutanamido]-3-hydroxy-1,6-diphenylhexan-2- ylcarbamate. 

k(S)-{(2S,3S,5S)-5-Amino-1,6-diphenyl-2-[(thiazol-5-ylmethoxy)carbonylamino]hexan-3-yl} 2-{3-[(2-isopropylthiazol-4-yl)methyl]-3- methylureido}-3-methylbutanoate. 

l Thiazol-5-ylmethyl (2S,3S,5S)-(5-t-butoxycarbonylamino)-3-hydroxy-1,6-diphenylhexan-2-ylcarbamate (may co-elute with isobutoxycarbonyl aminoalcohol). 

m Thiazol-5-ylmethyl (2S,3S,5S)-(5-isobutoxycarbonylamino)-3-hydroxy-1,6-diphenylhexan-2-ylcarbamate (may co-elute with BOC aminoalcohol). 

n(S)-N-[(S)-1-[(4S,5S)-4-Benzyl-2-oxooxazolidin-5-yl]-3-phenylpropan-2-yl]-2-{3-[(2-isopropylthiazol-4-yl)methyl]-3-methylureido}-3- methylbutanamide. 

o(S)-Isobutyl 2-{3-[(2-isopropylthiazol-4-yl)methyl]-3-methylureido}-3-methylbutanoate. 

p Thiazol-5-ylmethyl (2S,4S,5S)-4-hydroxy-5-[(S)-2-{3-[(2-isopropylthiazol-4-yl)methyl]-3-methylureido}-3-methylbutanamido]-1,6- diphenylhexan-2-ylcarbamate. 

q Thiazol-5-ylmethyl (2S,3R,5S)-3-hydroxy-5-[(S)-2-{3-[(2-isopropylthiazol-4-yl)methyl]-3-methylureido}-3-methylbutanamido]-1,6- diphenylhexan-2-ylcarbamate. 

r Bis(thiazol-5-ylmethyl) (2S,2'S,3S,3'S,5S,5'S)-5,5'-carbonylbis(azanediyl)bis(3-hydroxy-1,6-diphenylhexane-5,2-diyl)dicarbamate.

s Thiazol-5-ylmethyl (2S,3R,5R)-3-hydroxy-5-[(S)-2-{3-[(2-isopropylthiazol-4-yl)methyl]-3-methylureido}-3-methylbutanamido]-1,6- diphenylhexan-2-ylcarbamate. 

t Thiazol-5-ylmethyl (2S,3S,5R)-3-hydroxy-5-[(S)-2-{3-[(2-isopropylthiazol-4-yl)methyl]-3-methylureido}-3-methylbutanamido]-1,6- diphenylhexan-2-ylcarbamate. 

u (3S,4S,6S,10S,13S,15S,16S)-Bis(thiazol-5-ylmethyl)-4,15-dihydroxy-10-isopropyl-8,11-dioxo-3,6,13,16-tetrabenzyl-2,7,9,12,17- pentaazaoctadecanedioate. 

6 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight containers. Store at or below 30°. 

USP Reference Standards 〈11〉 

USP Ritonavir RS 

USP Ritonavir Related Compounds Mixture RS