Which of the following drugs does not activate opioid receptors, has been proposed as a drug in the management of opioid addiction and with just a single dose blocks the action of injected heroin for up to 48 hours ?
**Core Concept**
The question is testing the pharmacological properties of medications used in the management of opioid addiction. The desired medication should not activate opioid receptors but still effectively block the action of opioid drugs like heroin.
**Why the Correct Answer is Right**
Naltrexone is a medication that works as an opioid receptor antagonist. It does not activate opioid receptors and is used in the management of opioid addiction. Naltrexone has been shown to block the action of injected heroin for up to 48 hours after a single dose. This is because it binds to the opioid receptors in the brain, preventing heroin from exerting its effects. Naltrexone's mechanism of action involves competitive inhibition of opioid receptors, which are the same receptors targeted by heroin.
**Why Each Wrong Option is Incorrect**
* **Option A:** Methadone is an opioid receptor agonist, which means it activates opioid receptors and is used in the management of opioid addiction for this reason. It is not the correct answer because it activates opioid receptors.
* **Option B:** Buprenorphine is a partial opioid receptor agonist, which means it activates opioid receptors but to a lesser extent than full agonists like heroin. It is used in the management of opioid addiction but does not block the action of heroin like naltrexone.
* **Option D:** Naloxone is an opioid receptor antagonist, similar to naltrexone, but it has a shorter duration of action and is typically used as a rescue medication to reverse opioid overdose. It is not the correct answer because the question asks for a medication that blocks the action of heroin for up to 48 hours.
**Clinical Pearl / High-Yield Fact**
Naltrexone is an essential medication in the management of opioid addiction, and its use has been shown to reduce the risk of relapse. It is often used in conjunction with counseling and other forms of therapy.
**Correct Answer:** C. Naltrexone.