Pethidine Tablets

General Notices

Action and use

Opioid receptor agonist; analgesic.

Definition

Pethidine Tablets contain Pethidine Hydrochloride.

The tablets comply with the requirements stated under Tablets and with the following requirements.

Content of pethidine hydrochloride, C₁₅H₂₁NO₂,HCl

92.5 to 107.5% of the stated amount.

Identification

A. Shake a quantity of the powdered tablets containing 50 mg of Pethidine Hydrochloride with 20 mL of chloroform, filter, evaporate the filtrate to dryness and dry the residue at a pressure of 2 kPa. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of pethidine hydrochloride (RS 267).

B. Shake a quantity of the powdered tablets containing 0.2 g of Pethidine Hydrochloride with 20 mL of water and filter. To 5 mL of the filtrate add 10 mL of picric acid solution R1. The melting point of the crystals so obtained, after washing with water, is about 190°, Appendix V A.

Related substances

Carry out the method for thin-layer chromatography, Appendix III A, using kieselguhr G as the coating substance but allowing the solvent front to ascend 12 cm above the line of application. Impregnate the dry plate by placing it in a closed tank containing a mixture of 10 volumes of 2-phenoxyethanol and 90 volumes of acetone so that the plate dips about 5 mm beneath the surface of the liquid, allowing the impregnation solvent to ascend at least 15 cm, removing the plate from the tank and drying in a current of air. Use immediately, with the flow of the mobile phase in the same direction as the impregnation. Use as the mobile phase the upper layer obtained by shaking together 1 volume of diethylamine, 8 volumes of 2-phenoxyethanol and 100 volumes of petroleum spirit (boiling range, 50° to 70°) and allowing it to settle.

Apply separately to the plate 5 µL of each of the following solutions. For solution (1) use the upper layer obtained by shaking a quantity of the powdered tablets containing 0.1 g of Pethidine Hydrochloride with 5 mL of water, filtering, shaking the filtrate with 0.5 mL of 5m sodium hydroxide and 2 mL of ether and allowing the layers to separate. For solution (2) dilute 0.5 mL of solution (1) to 50 mL with ether.

After removal of the plate, allow it to dry in air for 10 minutes, return the plate to the tank and repeat the development. Remove the plate, allow it to dry in air for 10 minutes and spray with a 0.2% w/v solution of 2,7-dichlorofluorescein in methanol. Allow the plate to stand for 5 minutes and spray with water until the background is white to pale yellow. Examine in daylight. The chromatograms show red or orange spots. Any secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%). Examine without delay under ultraviolet light (365 nm). The chromatograms show spots with intense yellow fluorescence. Any secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%).

Assay

Weigh and powder 20 tablets. Dissolve a quantity of the powder containing 0.5 g of Pethidine Hydrochloride in 40 mL of water, add 2 mL of 5m sodium hydroxide and extract immediately with quantities of 25, 10 and 10 mL of chloroform. Wash each extract with the same 15 mL of water and filter into a dry flask. Titrate the combined extracts, which should be clear and free from droplets of water, with 0.05m perchloric acid VS using 0.15 mL of 1-naphtholbenzein solution as indicator. Each mL of 0.05m perchloric acid VS is equivalent to 14.19 mg of C₁₅H₂₁NO₂,HCl.