(Ph. Eur. monograph 1462)
C19H27NO 285.4 359-83-1
Action and use
Opioid receptor agonist; analgesic.
Preparation
Pentazocine Injection
DEFINITION
Pentazocine contains not less than 99.0 per cent and not more than the equivalent of 101.0 per cent of (2RS,6RS,11RS)-6,11-dimethyl-3-(3-methylbut-2-enyl)-1,2,3,4,5,6-hexahydro-2,6-methano-3-benzazocin-8-ol, calculated with reference to the dried substance.
CHARACTERS
A white or almost white powder, practically insoluble in water, freely soluble in methylene chloride and soluble in ethanol (96 per cent).
It shows polymorphism (5.9).
IDENTIFICATION
Examine by infrared absorption spectrophotometry (2.2.24), comparing with the Ph. Eur. reference spectrum for pentazocine (form A).
TESTS
Absorbance (2.2.25)
Dissolve 0.100 g in a mixture of 20 mL of water R and 1 mL of 1 M hydrochloric acid, and dilute to 100.0 mL with water R.
To 10.0 mL add 1 mL of 1 M hydrochloric acid and dilute to 100.0 mL with water R. The absorbance at the absorption maximum at 278 nm is 0.67 to 0.71, calculated with reference to the dried substance.
Related substances
Examine by thin-layer chromatography (2.2.27), using a TLC silica gel F254 plate R.
Test solution: Dissolve 0.20 g of the substance to be examined in methylene chloride R and dilute to 10 mL with the same solvent.
Reference solution (a): Dilute 1 mL of the test solution to 100 mL with methylene chloride R.
Reference solution (b): Dilute 5 mL of reference solution (a) to 10 mL with methylene chloride R.
Reference solution (c): Dilute 5 mL of reference solution (a) to 20 mL with methylene chloride R.
Apply to the plate 10 μL of each solution. Develop over a path corresponding to two thirds of the plate height using a mixture of 3 volumes of isopropylamine R, 3 volumes of methanol R and 94 volumes of methylene chloride R. Allow the plate to dry in air and examine in ultraviolet light at 254 nm. Heat the plate at 100-105 °C for 15 min, allow to cool, expose to iodine vapour and re-examine under ultraviolet light at 254 nm. By each method of visualisation: any spot in the chromatogram obtained with the test solution, apart from the principal spot, is not more intense than the spot obtained with reference solution (a) (1 per cent); not more than one such spot is more intense than the spot in the chromatogram obtained with reference solution (b) (0.5 per cent) and not more than 4 such spots are more intense than the spot in the chromatogram obtained with reference solution (c) (0.25 per cent).
Loss on drying (2.2.32)
Not more than 0.5 per cent, determined on 1.000 g by drying at 60 °C at a pressure not exceeding 0.7 kPa for 4 h.
Sulfated ash (2.4.14)
Not more than 0.1 per cent, determined on 1.0 g.
ASSAY
Dissolve 0.200 g in 50 mL of anhydrous acetic acid R. Titrate with 0.1 M perchloric acid, determining the end-point potentiometrically (2.2.20).
1 mL of 0.1 M perchloric acid is equivalent to 28.54 mg of C19H27NO.
STORAGE
Store protected from light.
