In this study, fluorescence quenching of acridine orange was observed when effective energy transfer occurred between alizarin red and acridine orange under aqueous conditions at a pH of 6.8. However, the quenched fluorescence in this aqueous solution could be partially recovered with the addition of an appropriate amount of venlafaxine hydrochloride. The recovery of fluorescence intensity had a good linear relationship with the amount of added venlafaxine hydrochloride. Based on this, a novel fluorescence recovery method for the determination of venlafaxine hydrochloride was established. The experimental results showed that under the optimal conditions, the linear range of this method was 3.49–31.4 mg L−1, the detection limit was 1.65 mg L−1, and the precision was 1.16%. The method was used for the determination of venlafaxine hydrochloride in sustained-release tablets and capsules with satisfactory results, and the recoveries were in the range of 95.5–105%.
