southern's work on the project was brief but intense; he officially worked on the script from november 16 to december 28, 1962. southern began to rely on the amphetamine-barbiturate "diet pill" dexamyl to keep him going through the frantic rewriting process; in later years, he developed a long-term amphetamine dependency. his amphetamine abuse, combined with his heavy intake of alcohol and other drugs, contributed significantly to health problems in later life.