Which of the following medications is not controlled?

Zetia, the medication identified as the correct answer, is not classified as a controlled substance. Controlled substances are drugs that have the potential for abuse and dependence, and thus are regulated more stringent. Zetia, which contains the active ingredient ezetimibe, is primarily used to lower cholesterol levels by reducing the amount of cholesterol absorbed by the intestines. It functions through a mechanism that does not involve any of the potential for abuse associated with controlled substances.

In contrast, Duragesic, which contains fentanyl, is a powerful opioid pain medication that is classified as a Schedule II controlled substance due to its high potential for abuse and risk of addiction. Inderal, containing propranolol, is a non-selective beta-blocker used to manage high blood pressure and anxiety, and while it is a prescription medication, it does not fall under the controlled substance category. Sinemet is a combination medication used to treat Parkinson’s disease, containing levodopa and carbidopa, and is also considered a controlled substance due to its potential effects related to movement and the brain's dopamine system. Therefore, Zetia stands out as the only option in the list that is not classified as controlled.