I know a little about the pharmacology of the benzodiazepines (e.g., Valium), which have been around for almost 50 years and have various uses in medicine, the least of them as a soporific. I have no knowledge of the pharmacology of Sonata or Ambien, relatively new soporifics without that range of therapeutic uses, but I don't think there is any concern that they "impede breathing, circulation, increase the muscle tone" in anyone well enough to board an airplane. (If someone were in a state of already compromised consciousness, these drugs might "impede breathing," but who would give/take these meds under such circumstances?)