Oxybutynin Chloride Tablets
DEFINITION
Oxybutynin Chloride Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of C22H31NO3·HCl.
IDENTIFICATION
•  Thin-Layer Chromatographic Identification Test 201
Sample solution:  Add a portion of powdered Tablets, equivalent to about 50 mg of oxybutynin chloride, to 10 mL of chloroform. Mix for two minutes, and centrifuge. Use the supernatant layer.
Developing solvent system:  Methanol
Visualization:  Iodine vapor
ASSAY
•  Procedure
Solution A:  Methanol, water, and triethylamine (800:3200:0.9). Adjust with phosphoric acid to a pH of 3.5 ± 0.05.
Mobile phase:  Acetonitrile and Solution A (1:4)
Standard solution:  0.05 mg/mL of USP Oxybutynin Chloride RS in Mobile phase
Sample solution:  Transfer an amount of powdered Tablets (from NLT 20 Tablets) nominally equivalent to 50 mg of oxybutynin chloride to a 1000-mL volumetric flask. Add about 400 mL of Mobile phase, sonicate for about 10 min, shake by mechanical means for about 45 min, and dilute with Mobile phase to volume.
Chromatographic system 
Mode:  LC
Detector:  UV 203 nm
Column:  4-mm × 30-cm; packing L10
Flow rate:  2 mL/min
Injection size:  20 µL
System suitability 
Sample:  Standard solution
Suitability requirements 
Tailing factor:  NMT 2.0
Relative standard deviation:  NMT 2.0%
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of C22H31NO3·HCl in the portion of Tablets taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of USP Oxybutynin Chloride RS in the Standard solution (mg/mL)
CU== nominal concentration of the Sample solution (mg/mL)
Acceptance criteria:  90.0%–110.0%
PERFORMANCE TESTS
•  Dissolution 711
Test 1 
Medium:  Water; 900 mL
Apparatus 2:  50 rpm
Time:  30 min
Sample solution:  Pass a portion of the solution under test through a suitable 0.45-µm filter. Dilute with Medium if necessary.
Analysis:  Determine the amount of C22H31NO3·HCl dissolved using the method set forth in the Assay, making any necessary modifications to the concentration of the Standard solution to correspond to that of the solution under test and injecting 100 µL of both solutions.
Tolerances:  NLT 80% (Q) of the labeled amount of C22H31NO3·HCl is dissolved.
Test 2:  If the products complies with this test, the labeling indicates that it meets USP Dissolution Test 2.
Medium:  0.01 N hydrochloric acid; 900 mL
Apparatus 2:  50 rpm
Time:  30 min
Standard solution:  5 µg/mL of USP Oxybutynin Chloride RS in Medium. This solution is stable for 5 days at ambient conditions.
Sample solution:  Pass a portion of the solution under test through a suitable 0.45-µm filter, discarding the first few mL.
Mobile phase:  Water, acetonitrile, and phosphoric acid (760:240:1)
Chromatographic system 
Mode:  LC
Detector:  UV 203 nm
Column:  4.6-mm × 7.5-cm; 3.5-µm packing L7
Column temperature:  40
Flow rate:  1.5 mL/min
Injection size:  100 µL
System suitability 
Sample:  Standard solution
Suitability requirements 
Tailing factor:  NMT 2.0
Relative standard deviation:  NMT 3.0%
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of oxybutynin chloride dissolved:
Result = (rU/rS) x (CS/L) x V x 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of oxybutynin chloride in the Standard solution
L== Tablet label claim (mg)
V== volume of Medium (mL), 900
Tolerances:  NLT 80% (Q) of the labeled amount of oxybutynin chloride is dissolved.
•  Uniformity of Dosage Units 905: Meet the requirements
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in tight, light-resistant containers.
•  Labeling: When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used.
•  USP Reference Standards 11
USP Oxybutynin Chloride RS Click to View Structure
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
711 Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
1-301-816-8106
(GCDF2010) General Chapters - Dosage Forms
Reference Standards RS Technical Services
1-301-816-8129
rstech@usp.org
USP35–NF30 Page 4166
Pharmacopeial Forum: Volume No. 35(1) Page 93