Complex sentence: They are also effective as anxiolytics, hypnotics, and anticonvulsalgesic effects; however, these effects are somewhat weak, preventing barbiturates from being used in surgery in the absence of other analgesics.
Split into simpler sentences: They are also effective as anxiolytics, hypnotics, and anticonvulsants. Barbiturates also have analgesic effects; however, these effects are somewhat weak, preventing barbiturates from being used in surgery in the absence of other analgesics.