A new thermo-optic analysis has been used to detect the photochemical reactions in salbutamol, a drug used as anti asthmatic/bronchodilator. Certain derived optic parameters of pure medicine and that exposed to solar radiations have been determined as a function of temperature. Plots of these parameters versus temperature have been made. The nature of variation and the relative shift in the curves for the exposed samples compared with the unexposed ones have been used to study photochemical reactions. The results have been explained in the light of existing theories and confirmed using UV absorption spectra of the samples.