Introduction

The question asks for an analgesic that does not cause addiction and mood modification. An analgesic is a medication that relieves pain, and addiction refers to the dependence or craving for a substance, while mood modification refers to altering one's emotional state. Out of the given options, N-Acetyl-para-aminophenol (commonly known as acetaminophen) is the only one that satisfies these criteria.

Explanation

Acetaminophen, commonly known by its brand name Tylenol, is a widely used analgesic and antipyretic (fever reducer). It is known to relieve pain without causing addiction or mood modification. Here's why:

1. Mechanism of Action
- Acetaminophen works by inhibiting the production of prostaglandins, which are substances in the body that cause pain and inflammation.
- Unlike opioids such as morphine, which bind to opioid receptors in the brain to relieve pain, acetaminophen does not directly interact with the opioid system. This lack of interaction with opioid receptors is believed to contribute to its lower addiction potential.

2. Addiction Potential
- Acetaminophen is not considered addictive because it does not activate the reward pathway in the brain, which is associated with addiction.
- It does not produce the euphoric effects or the intense pleasure associated with drugs like diazepam (a benzodiazepine) or tetrahydrocannabinol (THC), the psychoactive component of marijuana.
- Additionally, acetaminophen does not cause physical dependence or withdrawal symptoms when discontinued.

3. Mood Modification
- Acetaminophen primarily acts on the peripheral nervous system (outside the brain and spinal cord) to reduce pain and fever.
- It does not cross the blood-brain barrier easily, which means it has limited effects on the central nervous system.
- As a result, acetaminophen does not significantly alter mood or cause noticeable changes in emotional state.

Conclusion

In conclusion, acetaminophen (N-Acetyl-para-aminophenol) can be used as an analgesic without causing addiction or mood modification. Its mechanism of action, lack of interaction with the opioid system, and limited effects on the central nervous system contribute to its safety profile. It is important to note that while acetaminophen has a lower addiction potential compared to opioids, it should still be used responsibly and according to the recommended dosage to avoid potential liver toxicity.