Methods and systems for analyzing oscillatory fluorescence representing an oscillatory ion flux associated with one or more biological cells. An illustrative method of analysis may comprise detecting fluorescence from one or more biological cells to produce a series of data points describing an oscillation pattern. A series of slopes may be calculated for the oscillation pattern. For example, a sliding window may be used to define subsets of the series of data points from which the series of slopes are calculated. Peaks of the oscillation pattern may be identified using the series of slopes. Primary peaks and secondary peaks, if any, in the oscillation pattern may be identified and characterized by multiple measurements. An aspect of the secondary peaks may be determined. Appearance of secondary peaks may indicate a potential risk of cardiotoxicity or neurotoxicity.