Novel pamoate salts of certain 3-phenyl-3-dimethylaminoalkyl-4,4dimethylpiperidin-2,6-diones (1) and pharmacologically acceptable solvates thereof are devoid of the weight loss and hepatocyte changes in the rat which limited to marginally effective levels the permitted clinical doses of the corresponding hydrochlorides in the treatment or prophylaxis of stress-related affective disorders such as anxiety, depression, migraine and sleep apnoea. The preferred pamoate salts are 3(3,5dimethoxyphenyl)-3-(3-dimethylaminopropyl)-4,4-dimethylpiperidine-2,6-dione pamoate and, especially, 3(3-methoxyphenyl)-3-(3-dimethylaminopropyl)-4,4-dimethylpiperidine2,6-dione pamoate.