Doxycycline Capsules
Action and use
Tetracycline antibacterial.
Definition
Doxycycline Capsules contain Doxycycline Hyclate.
Content of anhydrous doxycycline, C22H24N2O8
95.0 to 105.0% of the stated amount.
Identification
Tests
Light-absorbing impurities
Dissolve the contents of five capsules as completely as possible in sufficient of a mixture of 1 volume of 1m hydrochloric acid and 99 volumes of methanol to produce a solution containing the equivalent of 1.0% w/v of anhydrous doxycycline and filter. The absorbance of the filtrate at 490 nm is not more than 0.20, calculated with reference to the dried capsule contents, Appendix II B.
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions prepared immediately before use. For solution (1) dissolve a quantity of the contents of the capsules containing the equivalent of 7.0 mg of anhydrous doxycycline in 10 mL of 0.01m hydrochloric acid, filter and use the filtrate. Solutions (2) to (5) are solutions in 0.01m hydrochloric acid containing (2) 0.080% w/v of doxycycline hyclate BPCRS, (3) 0.080% w/v of 6-epidoxycycline hydrochloride BPCRS, (4) 0.080% w/v of metacycline hydrochloride BPCRS and (5) 0.0016% w/v each of 6-epidoxycycline hydrochloride BPCRS and metacycline hydrochloride BPCRS. For solution (6) dilute a mixture of 4 volumes of solution (2), 1.5 volumes of solution (3) and 1 volume of solution (4) to 25 volumes with 0.01m hydrochloric acid.
The chromatographic procedure may be carried out using (a) a column (25 cm × 4.6 mm) packed with styrene-divinylbenzene co-polymer (8 µm) with a pore size of 10 nm (PLRP-S from Polymer Laboratories is suitable) and maintained at 60°, (b) as the mobile phase with a flow rate of 1 mL per minute a solution prepared as described below and (c) a detection wavelength of 254 nm. For the mobile phase add 60 g of 2-methylpropan-2-ol to a graduated flask with the aid of 200 mL of water, add 400 mL of phosphate buffer pH 8.0, 50 mL of a 1% w/v solution of tetrabutylammonium hydrogen sulfate previously adjusted to pH 8.0 with 2m sodium hydroxide and 10 mL of a 4% w/v solution of disodium edetate previously adjusted to pH 8.0 with 2m sodium hydroxide and dilute to 1000 mL with water. Inject 20 µL of each solution.
The test is not valid unless, in the chromatogram obtained with solution (6), the resolution factor between the first peak (metacycline) and the second peak (6-epidoxycycline) is at least 1.25 and the resolution factor between the second peak and the third peak (doxycycline) is at least 2.0. If necessary, adjust the content of 2-methylpropan-2-ol in the mobile phase.
In the chromatogram obtained with solution (1) the area of any peak corresponding to metacycline or 6-epidoxycycline is not greater than the area of the corresponding peak in the chromatogram obtained with solution (5) (2%, with reference to doxycycline hyclate) and the area of any other secondary peak is not greater than 0.25 times the area of the peak corresponding to 6-epidoxycycline in the chromatogram obtained with solution (5) (0.5%, with reference to doxycycline hyclate).
Loss on drying
When dried at 105° for 2 hours, the contents of the capsules lose not more than 8.5% of their weight. Use 1 g.
Assay
Carry out the method for liquid chromatography, Appendix III D, using the following solutions. For solution (1) dissolve the mixed contents of 20 capsules containing the equivalent of 17.5 mg of anhydrous doxycycline in sufficient 0.01m hydrochloric acid to produce 25 mL and dilute 4 mL of the solution to 25 mL with the same solvent. Solution (2) contains 0.0128% w/v of doxycycline hyclate BPCRS in 0.01m hydrochloric acid.
The chromatographic conditions described under Related substances may be used.
Calculate the content of C22H24N2O8 using the declared content of C22H24N2O8 in doxycycline hyclate BPCRS.
Labelling
The quantity of active ingredient is stated in terms of the equivalent amount of anhydrous doxycycline.