Parametrization of theoretical rate coefficients for chemically-activated reactions involving isomerization of activated complexes was examined. The theoretical rate coefficients were computed for chosen test reaction systems by using the Rice-Ramsperger-Kassel-Marcus theory. The low- and high-pressure-limit rate coefficients were found to be proportional to [M](i), where [M] is the bath gas density and i identifies a specific reaction channel. Several parametrization approaches to the pressure dependence of the rate coefficients were tested. The formulas based on a falloff broadening factor and the generalized interpolation between the pressure Limits produced generally large errors. Modifications were introduced that improve the accuracy of these previously suggested formulas. The most promising parametrization formula discovered in the present study contains only three temperature-dependent adjustable parameters and demonstrates a high level of accuracy, with maximum errors below 1% for most cases tested, including bath chemically-activated and unimolecular reactions.