Complex sentence: Sedative hypnotics, such as benzodiazepines, barbiturates and alcohol, cause the most serious medical complications during withdrawal and have been cited to be more clinically hazardous to withdraw from than opiates.
Split into simpler sentences: Sedative hypnotics, such as benzodiazepines, barbiturates and alcohol, cause the most serious medical complications during withdrawal. They are considered more clinically hazardous to withdraw from than opiates.