May cause anhidrosis and hyperthermia, which may be severe (risk increased in hot environments, particularly in the elderly, alcoholics, patients with CNS disease, and those with prolonged outdoor exposure). May be associated with confusion or hallucinations (generally at higher dosages). Intensification of symptoms or toxic psychosis may occur in mental disorders. May cause CNS depression. When given in large doses or to susceptible patients, may cause weakness and inability to move particular muscle groups. Use with caution in tachycardia, cardiac arrhythmias, hypertension, or hypotension. Use with caution in genitourinary obstruction, in hepatic or renal impairment, and in prostatic hyperplasia and/or urinary stricture or retention. The elderly frequently develop increased sensitivity (side-effects may be more severe in elderly patients with atherosclerotic changes).