Basics and Applications of Solid-State Kinetics: A Pharmaceutical Perspective**The authors dedicate this review to the memory of Dr. David J.W. Grant who passed away on December 9, 2005. Dr. Grant was an internationally known authority at the University of Minnesota on the solid-state properties of drugs. He will be remembered as a kind, humble, and brilliant scholar.

Most solid-state kinetic principles were derived from those for homogenous phases in the past century. Rate laws describing solid-state degradation are more complex than those in homogenous phases. Solid-state kinetic reactions can be mechanistically classified as nucleation, geometrical contraction, diffusion, and reaction order models. Experimentally, solid-state kinetics is studied either isothermally or nonisothermally. Many mathematical methods have been developed to interpret experimental data for both heating protocols. These methods generally fall into one of two categories: model-fitting and model-free. Controversies have arisen with regard to interpreting solid-state kinetic results, which include variable activation energy, calculation methods, and kinetic compensation effects. Solid-state kinetic studies have appeared in the pharmaceutical literature over many years; some of the more recent ones are discussed in this review.