Final answer:
Codeine and morphine can be classified as Schedule III substances when mixed with other non-narcotic agents and are within the accepted limits. Heroin, however, remains a Schedule I drug due to its high abuse potential and lack of accepted medical use in the U.S.
Step-by-step explanation:
When mixed with other non-narcotic agents, codeine may be classified as a Schedule III substance, so long as it does not exceed the maximum allowable limits. Codeine, when found in combination products with a limited amount of non-narcotic medicinal ingredients, can be classified under this scheduling. Morphine, another opioid derived from the opium poppy, is used to relieve severe pain, often before and after surgical procedures and can be mixed with other agents to create Schedule III drugs as long as they adhere to established limits.
It is important to note that not all drugs derived from the opium poppy are eligible for Schedule III classification when mixed. Heroin, which is a chemically modified version of morphine and known for its strong addictive properties, remains classified as a Schedule I substance due to its high potential for abuse and no currently accepted medical use in treatment in the United States. The Drug Enforcement Administration (DEA) carefully regulates and schedules substances based on their potential for abuse and accepted medical use.