A clinical trial compairing sustained release amitriptyline (Amitriptyline, retard) and conventional amitriptyline tablets (Amitriptylin) in endogenously depressed patients with simultaneous determination of serum levels of amitriptyline and nortriptyline. - Liisberg,P.; Mose,H.; Amdisen,A.; Jorgensen,A.; Hopfner Petersen,H.E. (Acta Psychiat Scand, 1978)