Conformational study on neuromuscular blocking drugs is relatively new and developing. Traditional SAR studies do not specify environmental factors on molecules. Computer-based conformational searches assume that the molecules are in vacuo, which is not the case in vivo. Solvation models take into account the effect of a solvent on the conformation of the molecule. However, no system of solvation can mimic the effect of the complex fluid composition of the body.
The division of muscle relaxants to rigid and non-rigid is at most qualitative. The energy required for conformational changes may give a more precise and quantitative picture. Energy required for reducing onium head distance in the longer muscle relaxant chains may quantify their ability to bend and fit its receptive sites. Using computers it is possible to calculate the lowest energy state conformer and thus most populated and best representing the molecule. This state is referred to as the global minimum. The global minimum for some simple molecules can be discovered quite easily with certainty. Such as for decamethonium the straight line conformer is clearly the lowest energy state. Some molecules, on the other hand, have many rotatable bonds and their global minimum can only be approximated.