Stability indicating spectrofluorimetric method for determination of duloxetine hydrochloride in bulk and in dosage form

Duloxetine (DLX), is a selective serotonin-norepinephrine reuptake inhibitor (SNRI) recommended for maintenance treatment of major depressive disorder, neuropathic pain especially diabetic polyneuropathy (first-line treatment), generalized anxiety disorder, stress urinary incontinence and fibromyalgia. The present investigation describes the validation of rapid, sensitive, cost effective and reproducible stability indicating spectrofluorometric methods based on the native fluorescence of duloxetine HCl in acidic medium for the estimation of duloxetine HCl in bulk and in formulations. The fluorescence intensity of duloxetine hydrochloride was measured at 336 nm after excitation at 290 nm. The methods were validated with respect to linearity, accuracy, precision and robustness. Linearity was observed in the concentration range of 0.3-30 μg/ml with an excellent correlation coefficients (r) ranging from 0.9940-0.9996. The limits of assay detection values were found to range from 0.56-0.89 μg/ml and quantitation limits ranged from 1.69-2.42 μg/ml for the proposed methods. The proposed method was applicable to the determination of the drug in capsules and the percentage recovery was found to range from 99.53 ± 99.66%. The proposed methods were developed as stability indicating procedures by carrying out the analysis for duloxetine hydrochloride on stressed samples prepared under various forced degradation conditions.