An analgesic is a medication that relieves pain. Let's analyze each option:
- Morphene (Morphine): This is a powerful opioid analgesic used to treat severe pain.
- Heroin: This is also an opioid analgesic, though it is highly addictive and illegal in most countries.
- Codeine: This is a milder opioid analgesic often used to treat moderate pain.
- Ranitidine: This is an H2-receptor antagonist, used to reduce stomach acid production. It is not an analgesic.
Therefore, Ranitidine is the only option that is not an analgesic.
The correct answer is:
Option 4: Ranitidine