Dextropropoxyphene Capsules

General Notices

Action and use

Opioid receptor agonist; analgesic.

Definition

Dextropropoxyphene Capsules contain Dextropropoxyphene Napsilate.

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

Content of dextropropoxyphene, C22H29NO2

92.5 to 107.5% of the stated amount.

Identification

Shake a quantity of the contents of the capsules containing the equivalent of 0.15 g of dextropropoxyphene with 5 mL of chloroform and filter. The filtrate complies with the following tests.

A. Evaporate 3 mL to dryness and dry the residue at 105° for 1 hour. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of dextropropoxyphene napsilate (RS 092).
B. Evaporate 0.05 mL in a porcelain dish and streak the spot with sulfuric acid containing 0.05 mL of formaldehyde solution per mL. A purple colour is produced.
C. Evaporate 0.4 mL on a piece of filter paper and burn the residue by the method for oxygen-flask combustion, Appendix VIII C, using 5 mL of 1.25m sodium hydroxide as the absorbing liquid. When the process is complete, dilute the liquid to 25 mL with water. To 5 mL of the solution so obtained add 1 mL of hydrogen peroxide solution (100 vol) and 1 mL of 1m hydrochloric acid, mix and add 0.05 mL of barium chloride solution. The solution becomes turbid.

Assay

Stir a quantity of the mixed contents of 20 capsules containing the equivalent of 0.5 g of dextropropoxyphene with 25 mL of chloroform and filter through absorbent cotton, washing the flask and filter with small quantities of chloroform. Add to the combined filtrates a mixture of 50 mL of water and 5 mL of 5m sodium hydroxide, shake, allow the layers to separate and wash the chloroform extract with 25 mL of water. Extract the aqueous layer with five 25 mL quantities of chloroform, washing each extract with the 25 mL of water and adding it to the original extract. Dry the combined extracts with anhydrous sodium sulfate, evaporate to about 3 mL on a water bath in a current of air, remove from the water bath and allow to evaporate to dryness at room temperature. Carry out Method I for non-aqueous titration, Appendix VIII A, on the residue using crystal violet solution as indicator. Each mL of 0.1m perchloric acid VS is equivalent to 33.95 mg of C22H29NO2.

Labelling

The quantity of active ingredient is stated in terms of the equivalent amount of dextropropoxyphene.