Selective analytical determination of cinchocaine hydrochloride in presence of its degradation products or in its binary mixture with hydrocortisone

ABSTRACT

Cinchocaine HCI was degraded by refluxing with 2N HCI for 4 hr. The degradation products were isolated and their structures were confirmed by IR and mass spectrophotometry. Cinchocaine HCI was then determined in presence of its degradation products by spectrophotometric and spectro-densitometric techniques. For the spectrophotometric methods, cinchocai ne HCI was determined by first derivative spectrophotometry [Dl] at 333.6 nm or by first derivative ratio spectrophotometry [DDI] at 301.6 or 332 nm in concentration ranges 5-80 microg/ml. For the spectro-densitometric method, silica gel plates were used together with benzene acetone methanol 25% NH3 [530.50.1, v/v] as developing solvent and the Rf values were 0.55, 0.12 and zero for cinchocaine HCI and its degradation products, respectively. Cinchocainc HCI and hydrocortisone binary mixture can be determined by the aforementioned densitometric method in concentration ranges 2-20 microg/spot and 2-16 microg/spot for cinchocaine HCI and hydrocortisone, respectively. Alternatively, cinchocaine HCI can be determined spectrophotometrically at 327.8 nm without any interference from hydrocortisone, while hydrocortisone was determined by third derivative spectrophotometry [D3] at 254 and 275.8 nm in concentration ranges 10-100 microg/ml and 5-35 microg/ml for cinchocaine HCI and hydrocortisone, respectively. The proposed methods were successfully applied for the analysis of laboratory prepared mixtures containing cinchocaine HCI and different percentages of its degradation products or cinchocaine HCI and hydrocortisone. These methods were also applied for the analysis of pharmaceutical dosage forms and the results obtained were assessed by the standard addition technique. Local anesthetics produce anesthesia by blocking sodium channels in the axonal membrane, reducing sodium conductance; this in turn reduces the rate and degree of depolarization of the nerve cell and prevents propagation of the action potential.[1] The local anesthetics should be soluble in water and should be effective when injected into tissue or when applied topically to mucous membranesi[2]. Local anesthetics are available as gel, ointments, creams and spray to provide reversible block of conduction along cutaneous nerves[3]. Cinchocaine HCI is a local anesthetic that was formerly used as nerve block and spinal anesthesia, but now, it is available only in topical form[4]. Hydrocortisone is a famous anti-inflammatory agent and it is incorporated with cinchocaine HCI in pharmaceutical preparation for treatment of haemorrhoid[3] Several methods have been described for the determination of cinchocaine HCI. These include spectrophotometric methods [5-15], fluorimetric methods [16-18] HPLC [19-22], TLC [23-27], GC [28-29] NMR [30-31] polarographic methods [32-33] and titrimetric methods [34-37] This work describes spectro-densitometric and spectrophotometric methods for the selective determination of cinchocaine HCI in presence of its two acid degradation products or in combination with hydrocortisone