Pro-drug compounds of the formula or and compositions containing them are provided that when administered to humans or other mammals provide an increased duration of active compound in the plasma compared to compounds of corresponding structure in which labile groups are not present. The side panels are movable from a retracted position wherein the side panels are disposed in parallel planes perpendicular to the top panel to a non-retracted position wherein the side panels are disposed at an acute angle to the planes. The macro class is embedded as a keyword within the template, so that when the template reaches the keyword, the template calls the macro class to further process the text file. The first channel material is spaced from the gate by one or more insulative materials. Matching splines provided on the central bore of the inner race and the yoke couple the inner race and the yoke for rotation.