The ACMD has given the following advice:
Lisdexamfetamine
Lisdexamfetamine is itself an inactive pro-drug but it is rapidly metabolised to dexamphetamine which then has the potential to exert the physical and social harms associated with amphetamines as a class although there may be some differences attributable to its prolonged pharmacokinetic profile.
Z class drugs
Z-drugs and benzodiazepines share the same basic mechanism of pharmacological action. There are no very significant differences in therapeutic efficacy or adverse effect potential between benzodiazepines and z-drugs, or between the z-drugs themselves. The suggested differences that have been reported, include a reduced abuse potential and propensity to tolerance and withdrawal with z-drugs compared to benzodiazepines.