Numerical simulations of the interaction of transient, dissipating gravity wave packets with the minor species involved in the OH airglow chemistry in the mesopause region reveal large wave-driven downward fluxes of the minor species. In addition to the minor species fluctuating in response to the wave, a strong secular variation of minor species densities occurs. At 90 km altitude this secular variation becomes significant ~80 min after the wave packet onset, and increases approximately linearly with increasing time for the following 2 hours. At later times the secular variation diminishes. Heating rates due to exothermic chemical reactions consequently exhibit a fluctuating component as well as a secular variation. When averaged over time, the net effect of each of the two waves considered is to cause large (~22% and 37%) increases in average heating rates. This secular variation in heating rates could be more significant than the present results suggest because larger amplitude gravity waves can exist in the mesopause region.