Final answer:
The volume limit for OTC products containing opium to a purchaser who is 18 or older depends on the specific product and the laws regulating opium. Opium is a controlled substance regulated by the DEA in the United States. OTC products containing opium are only available through a healthcare professional with a valid prescription.
Step-by-step explanation:
The volume limit for over-the-counter (OTC) products containing opium to a purchaser who is 18 or older can vary depending on the specific product. However, it is important to note that opium is a controlled substance and is regulated by law.
In the United States, the Drug Enforcement Administration (DEA) classifies opium as a Schedule II drug, which means it has a high potential for abuse and may lead to severe physical or psychological dependence.
Therefore, it is illegal to purchase or possess opium without a valid prescription from a healthcare professional. OTC products containing opium, such as cough medicines, are not available without a prescription. They are only available in prescription-strength formulations and can only be obtained through a healthcare professional.