Doxycycline Capsules

General Notices

Action and use

Tetracycline antibacterial.

Definition

Doxycycline Capsules contain Doxycycline Hyclate.

The capsules comply with the requirements stated under Capsules and with the following requirements.

Content of anhydrous doxycycline, C22H24N2O8

95.0 to 105.0% of the stated amount.

Identification

A. Carry out the method for thin-layer chromatography, Appendix III A, using silica gel H as the coating substance and a mixture of 6 volumes of water, 35 volumes of methanol and 59 volumes of dichloromethane as the mobile phase. Spray the plate evenly with a 10% w/v solution of disodium edetate the pH of which has been adjusted to 9.0 with 10m sodium hydroxide (about 10 mL for a 100 mm × 200 mm plate). Allow the plate to dry in a horizontal position for at least 1 hour. Immediately before use dry it at 110° for 1 hour. Apply separately to the plate 1 µL of each of the following solutions. For solution (1) shake a quantity of the contents of the capsules containing the equivalent of 50 mg of anhydrous doxycycline with 100 mL of methanol for 1 to 2 minutes, centrifuge and use the supernatant liquid. Solution (2) contains 0.05% w/v of doxycycline hyclate BPCRS in methanol. Solution (3) contains 0.05% w/v each of doxycycline hyclate BPCRS and tetracycline hydrochloride BPCRS in methanol. After removal of the plate, dry it in a current of air and examine under ultraviolet light (365 nm). The principal spot in the chromatogram obtained with solution (1) is similar in position, colour and size to that in the chromatogram obtained with solution (2). The test is not valid unless the chromatogram obtained with solution (3) shows two clearly separated spots.
B. To 0.5 mg of the contents of the capsules add 2 mL of sulfuric acid. A yellow colour is produced.
C. The contents of the capsules yield the reactions characteristic of chlorides, Appendix VI.

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.