Action and use
Immunostimulant; antihelminthic.
DEFINITION
Levamisole Oral Solution is an aqueous solution of Levamisole Hydrochloride.
The oral solution complies with the requirements stated under Oral Liquids and with the following requirements.
Content of levamisole hydrochloride, C11H12N2S,HCl
92.5 to 107.5% of the stated amount.
IDENTIFICATION
A. Carry out the method for thin-layer chromatography, Appendix III A, using silica gel G as the coating substance and a mixture of 1 volume of 13.5M ammonia, 10 volumes of methanol and 100 volumes of ethyl acetate as the mobile phase. Apply separately to the plate 1 μL of each of the following solutions. For solution (1) dilute a volume of the oral solution with methanol to produce a solution containing 1% w/v of Levamisole Hydrochloride. Solution (2) contains 1% w/v of levamisole hydrochloride BPCRS in methanol. After removal of the plate, allow it to dry in air and spray with potassium iodoplatinate solution. The principal spot in the chromatogram obtained with solution (1) corresponds to that in the chromatogram obtained with solution (2).
B. To a quantity of the oral solution containing 0.3 g of Levamisole Hydrochloride add 10 mL of water and 6 mL of 1M sodium hydroxide. Extract with 20 mL of dichloromethane, discard the aqueous layer and wash the dichloromethane layer with 10 mL of water. Shake with anhydrous sodium sulfate, filter and evaporate the dichloromethane at room temperature. The melting point of the residue, after drying over phosphorus pentoxide at a pressure of 1.5 to 2.5 kPa at a temperature not exceeding 40°, is about 59°, Appendix V A.
C. The oral solution is laevorotatory.
2,3-Dihydro-6-phenylimidazo[2,1-b]thiazole hydrochloride
Carry out the method for thin-layer chromatography, Appendix III A, using silica gel G as the coating substance and a mixture of 8 volumes of glacial acetic acid, 16 volumes of methanol and 90 volumes of toluene as the mobile phase. Apply separately to the plate 50 μL of solution (1) and 10 μL of solution (2). For solution (1) dilute a volume of the oral solution to produce a solution containing 1.0% w/v of Levamisole Hydrochloride. Solution (2) contains 0.021% w/v of 2,3-dihydro-6-
phenylimidazo[2,1-b]thiazole BPCRS in methanol. After removal of the plate, allow it to dry in air and spray with potassium iodoplatinate solution. Any spot in the chromatogram obtained with solution (1) corresponding to 2,3-dihydro-6-phenylimidazo[2,1-b]thiazole is not more intense than the spot in the chromatogram obtained with solution (2) (0.5%).
ASSAY
To a volume of the oral solution containing 0.75 g of Levamisole Hydrochloride add 15 mL of 2M sodium hydroxide, extract with three quantities, of 25 mL, 20 mL and 15 mL, of chloroform, wash the combined extracts with two 10 mL quantities of
Levamisole Oral Solution water and discard the washings. To the clear chloroform solution, after drying with anhydrous sodium sulfate if necessary, add 50 mL of anhydrous acetic acid. Carry out Method I for non-aqueous titration, Appendix VIII A, using 1-naphtholbenzein solution as indicator. Each mL of 0.1M perchloric acid VS is equivalent to 24.08 mg of C11H12N2S,HCl.
