Hydrochlorothiazide Capsules
DEFINITION
Hydrochlorothiazide Capsules contain NLT 90.0% and NMT 110.0% of the labeled amount of hydrochlorothiazide (C7H8ClN3O4S2).
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.
ASSAY
•  Procedure
Buffer:  13.8 g/L of monobasic sodium phosphate
Mobile phase:  Acetonitrile and Buffer (10:90). Adjust with 10% (v/v) phosphoric acid to a pH of 3.0 ± 0.1. Pass through a filter of 0.45-µm pore size.
System suitability solution:  0.15 mg/mL of each of USP Hydrochlorothiazide RS and USP Chlorothiazide RS in Mobile phase. Sonicate to completely dissolve.
Standard stock solution:  0.50 mg/mL solution prepared as follows: Dissolve a quantity of USP Hydrochlorothiazide RS in acetonitrile (10% of the volume of the flask), and dilute with Mobile phase. Sonicate to completely dissolve.
Standard solution:  50 µg/mL solution in Mobile phase from the Standard stock solution. Sonicate to completely dissolve.
Sample stock solution:  0.25 mg/mL of hydrochlorothiazide solution prepared as follows: Transfer a number of Capsules into a suitable volumetric flask. Add water, 10% of the volume of the flask, and sonicate for 10 min with vigorous shaking. Add Buffer, 20% of the volume of the flask, and again sonicate for 10 min. Add acetonitrile up to 40% of the volume of the flask, and sonicate for 30 min. Dilute with Buffer to volume, and pass through a suitable filter of 0.45-µm pore size.
Sample solution:  50 µg/mL of hydrochlorothiazide in Mobile phase from Sample stock solution
Chromatographic system 
Mode:  LC
Detector:  UV 272 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  2.0 mL/min
Injection size:  20 µL
System suitability 
Samples:  System suitability solution and Standard solution
Suitability requirements 
Resolution:  NLT 2.0 between chlorothiazide and hydrochlorothiazide, System suitability solution
Tailing factor:  NMT 2.0, Standard solution
Column efficiency:  NLT 4000 theoretical plates, Standard solution
Relative standard deviation:  NMT 2.0%, Standard solution
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of the labeled amount of hydrochlorothiazide (C7H8ClN3O4S2) in the portion of Capsules taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response of hydrochlorothiazide from the Sample solution
rS== peak response of hydrochlorothiazide from the Standard solution
CS== concentration of hydrochlorothiazide in the Standard solution (µg/mL)
CU== nominal concentration of hydrochlorothiazide in the Sample solution (µg/mL)
Acceptance criteria:  90.0%–110.0%
PERFORMANCE TESTS
•  Dissolution 711
Medium:  0.1 N hydrochloric acid; 900 mL
Apparatus 1:  100 rpm
Time:  30 min
Standard solution:  6.75-µg/mL solution prepared as follows: Dissolve a quantity of USP Hydrochlorothiazide RS in acetonitrile (10% of the volume of the flask), and dilute with Medium. Sonicate to completely dissolve.
Sample solution:  Pass a portion of the solution under test through a suitable filter of 0.45-µm pore size. Dilute with Medium to a concentration similar to the Standard solution.
Analytical wavelength:  UV 272 nm
Pathlength:  1 cm
Blank:  Medium
Calculate the percentage of the labeled amount of hydrochlorothiazide (C7H8ClN3O4S2) dissolved:
Result = (AU/AS) × (CS/L) × D × V × 100
AU == absorbance of the Sample solution
AS== absorbance of the Standard solution
CS== concentration of hydrochlorothiazide in the Standard solution (mg/mL)
L== label claim (mg/Capsule)
D== dilution for the Sample solution
V== volume of Medium, 900 mL
Tolerances:  NLT 80% (Q) of the labeled amount of hydrochlorothiazide (C7H8ClN3O4S2) is dissolved.
•  Uniformity of Dosage Units 905: Meet the requirements
IMPURITIES
Organic Impurities 
•  Procedure
Buffer, Mobile phase, System suitability solution, and Chromatographic system:  Proceed as directed in the Assay.
Standard stock solution:  0.25-mg/mL solution prepared as follows: Dissolve a quantity of USP Hydrochlorothiazide RS in acetonitrile (10% of the volume of the flask), and dilute with Mobile phase.
Standard solution:  0.25 µg/mL of USP Hydrochlorothiazide RS in Mobile phase from Standard stock solution
Sample solution:  Use the Sample stock solution as prepared in the Assay.
Suitability requirements 
Samples:  System suitability solution and Standard solution
Resolution:  NLT 2.0 between chlorothiazide and hydrochlorothiazide, System suitability solution
Tailing factor:  NMT 2.0, Standard solution
Column efficiency:  NLT 4000 theoretical plates, Standard solution
Relative standard deviation:  NMT 5.0%, Standard solution
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of each individual impurity in the portion of Capsules taken:
Result = (rU/rS) × (CS/CU) × (1/F) × 100
rU== peak response of each individual impurity from the Sample solution
rS== peak response of hydrochlorothiazide from the Standard solution
CS== concentration of hydrochlorothiazide in the Standard solution (µg/mL)
CU== nominal concentration of hydrochlorothiazide in the Sample solution (µg/mL)
F== relative response factor (see Table 1)
Acceptance criteria 
Individual impurities:  See Table 1.
Total impurities:  NMT 1.5%.
Table 1
Name Relative
Retention
Time
Relative
Response
Factor
Acceptance
Criteria,
NMT (%)
Benzothiadiazine
related compound Aa
0.65 0.61 1.0
Chlorothiazide 0.80 a
Hydrochlorothiazide 1.0 1.0
5-Chlorohydrochlorothiazide 2.88 a
Any other
individual unspecifed
degradant
1.0 0.2
Total impuritiesb   1.5
a  Process related impurity. Relative retention time is given for identification.
b  Total impurities include benzothiadiazine related compound A and all unknown degradation impurities. Disregard any peak less than 0.05%.
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in well-closed containers, and store at controlled room temperature.
•  USP Reference Standards 11
USP Hydrochlorothiazide RS Click to View Structure
USP Chlorothiazide RS Click to View Structure
2H-1,2,4-Benzothiadiazine-7-sulfonamide, 6-chloro-, 1,1-dioxide.
    C7H6ClN3O4S2        295.72
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Topic/Question Contact Expert Committee
Monograph Sujatha Ramakrishna, Ph.D.
Senior Scientific Liaison
1-301-816-8349
(SM22010) Monographs - Small Molecules 2
711 Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
1-301-816-8106
(GCDF2010) General Chapters - Dosage Forms
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USP35–NF30 Page 3422
Pharmacopeial Forum: Volume No. 36(2) Page 405