Which of the following is not a narcotic drug?

• A. Oxycodone
• B. Opium
• C. Codeine
• D. Diphenhydramine

Answer: (D)

The concept being tested is what counts as a narcotic in medical and pharmacology terms. Narcotics are typically opioids—drugs that act on opioid receptors to relieve pain, often with potential for sedation, euphoria, and dependence. Oxycodone, opium, and codeine are classic examples of opioids and are classified as narcotics because of their analgesic effects and capacity for misuse.

Diphenhydramine, by contrast, is an antihistamine used mainly for allergies and sometimes as a sleep aid. It does not act on opioid receptors and does not produce the same analgesic or dependence-related effects that define narcotics. It can cause drowsiness, but that sedative effect comes from blocking histamine receptors, not from opioid activity. So, the option that is not a narcotic is diphenhydramine.