Oxybutynin Tablets
Oxybutynin Hydrochloride Tablets; Oxybutynin Chloride Tablets
Oxybutynin Tablets contain not less than 95.0 per cent and not more than 105.0 per cent of the stated amount of oxybutynin hydrochloride, C22H31NO3,HCl.
Usual strengths. 2.5 mg; 5.0 mg.
Identification
To a quantity of the powdered tablets containing 25 mg of Oxybutynin Hydrochloride, add sufficient 2M sodium hydroxide adjust to pH 12.0 and extract with four 20-ml quantities of hexane. Filter the collected hexane layers through anhydrous sodium sulphate and evaporate to dryness. On the residue, determine by infrared absorptionspectrophotometry (2.4.6). Compare the spectrum obtained with oxybutynin Hydrochloride RS treated in the same manner or with the reference spectrum of oxybutynin.
Tests
Dissolution (2.5.2).
Apparatus No. 1,
Medium. 900 ml of water,
Speed and time. 50 rpm and 45 minutes.
Withdraw a suitable volume of the medium and filter.
Determine by liquid chromatography (2.4.14).
Test solution. Use the filtrate, diluted if necessary, with the dissolution medium, discard the first few ml of filtrate.
Reference solution. A 0.0005 per cent w/v solution of oxybutynin hydrochloride RS in the dissolution medium, diluted further if necessary.
Use the chromatographic system as described under Assay.
Calculate the content of C22H31NO3,HCl.
- Not less than 75 per cent of the stated amount of C22H31NO3, HCl.
Related substances. Determine by liquid chromatography (2.4.14).
Test solution. Dissolve a quantity of the powdered tablets containing about 50 mg of Oxybutynin Hydrochloride in 40 ml of 0.01 M hydrochloric acid with the aid of ultrasound for 15 minutes and dilute to 50.0 ml with same solvent and filter.
Reference solution (a). A 0.0015 per cent w/v solution of oxybutynin impurity A RS [4-(diethylamino)but-2-ynyl (RS)-2-(cyclohex-3-enyl)-2-cyclohexyl-2-hydroxyacetate] in 0.01 M hydrochloric acid.
Reference solution (b). A 0.001 per cent w/v solution of phenylcyclohexylglycolic acid RS [(RS)-2-cyclohexyl-2-hydroxy-2-phenylacetic acid (phenylcyclohexylglycolic acid)] in 0.01 M hydrochloric acid.
Reference solution (c). Dilute 1.0 ml of test solution to 200.0 ml with 0.01 M hydrochloric acid.
Reference solution (d). A 0.001 per cent w/v solution of oxybutynin impurity A RS in reference solution (c).
Chromatographic system
– a stainless steel column 15 cm x 4.6 mm, packed with octadecylsilane bonded to porous silica (5 µm)
– mobile phase: A. a mixture of 0.34 per cent w/v solution of potassium dihydrogen orthophosphate and 0.436 per cent w/v solution of dipotassium hydrogen orthophosphate,
- acetonitrile,
– a gradient programme using the conditions given below,
– flow rate: 1 ml per minute,
– spectrophotometer set at 210 nm,
– injection volume: 50 µl.
Time Mobile phase A Mobile phase B
(in min) (per cent v/v) (per cent v/v)
0 70 30
5 70 30
6 45 55
50 45 55
51 70 30
60 70 30
The retention time are about 31 minutes for the peaks due to oxybutynin hydrochloride and about 47 minutes for oxybutynin impurity A.
Inject reference solution (d). The test is not valid unless the resolution between the peaks due to oxybutynin hydrochloride and oxybutynin impurity A is not less than 10.0
Inject reference solution (a), (b), (c) and the test solution. In the chromatogram obtained with the test solution, the area of the peak corresponding to oxybutynin impurity A is not more than the area of the principal peak in the chromatogram obtained with reference solution (a) (1.5 per cent) and the area of the peak corresponding to phenylcyclohexylglycolic acid is not more than half the area of the principal peak in the chromatogram obtained with reference solution (b) (0.5 per cent). The area of the any other secondary peak is not more than 0.4 times the area of the principal peak in the chromatogram obtained with reference solution (c) (0.2 per cent) and the sum of areas of all the secondary peaks is not more than the area of the peak in the chromatogram obtained with reference solution (c) (0.5 per cent). Ignore any peak with an area less than 0.1 times the area of the principal peak in the chromatogram obtained with reference solution (c) (0.05 per cent).
Uniformity of content. Complies with the test stated under Tablets.
Determine by liquid chromatography (2.4.14), as described under Assay, using the following solutions.
Test solution. Disperse one tablet in 0.01 M hydrochloric acid, sonicate and dilute if necessary to obtain a solution containing 0.005 per cent w/v of oxybutynin hydrochloride in 0.01 M hydrochloric acid.
Other tests. Comply with the tests stated under Tablets.
Assay. Determine by liquid chromatography (2.4.14).
Test solution. Weigh and powder 20 tablets. Disperse a quantity of powder containing 25 mg of Oxybutynin Hydrochloride with 400 ml of 0.01M hydrochloric acid, with the aid of ultrasound for 20 minutes and dilute to 500.0 ml with 0.01 M hydrochloric acid mix and filter.
Reference solution. A 0.005 per cent w/v solution of oxybutynin hydrochloride RS in 0.01 M hydrochloric acid.
Charomatographic system
– a stainless steel column 15 cm x 4.6 mm, packed with nitrile groups chemically bonded to porous silica
(5 µm),
– column temperature: 40º,
– mobile phase: a mixture of 300 volumes of acetonitrile and 700 volumes of 0.48 per cent w/v solution of anhydrous potassium dihydrogen orthophosphate previously adjusted to pH 3.0 to 3.5 with orthophosphoric acid.
– flow rate: 2.0 ml per minute,
– spectrophotometer set at 200 nm,
– injection volume: 20 µl.
Inject the reference solution and the test solution.
Calculate the content of C22H31NO3, HCl in the tablets.
Storage: Store protected from moisture, at a temperature not exceeding 30˚.