Which one of the following is NOT true with morphine?
**Core Concept**
Morphine is a potent opioid analgesic that primarily acts on the mu-opioid receptors in the central nervous system, leading to its analgesic, sedative, and respiratory depressant effects. The correct understanding of morphine's pharmacological properties is crucial for its safe and effective use in clinical practice.
**Why the Correct Answer is Right**
Morphine exerts its analgesic effect by activating the mu-opioid receptors in the spinal cord and brain, which leads to the inhibition of pain transmission. It also causes respiratory depression by stimulating the delta-opioid receptors in the brainstem, resulting in a decrease in the respiratory rate. Additionally, morphine can cause physical dependence and addiction due to its ability to activate the reward centers in the brain.
**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true, as morphine does indeed cause constipation by slowing down the movement of food through the intestines and increasing water absorption.
**Option B:** This statement is true, as morphine can cause histamine release, leading to vasodilation and increased vascular permeability, resulting in hypotension and potentially anaphylactoid reactions.
**Option C:** This statement is true, as morphine can cause hypogonadism in males by inhibiting the release of gonadotropin-releasing hormone (GnRH), which in turn leads to decreased testosterone production.
**Clinical Pearl / High-Yield Fact**
Morphine's analgesic effect is dose-dependent and can be enhanced by the concurrent administration of other opioids, such as naloxone, which acts as an antidote to reverse opioid-induced respiratory depression.
**Correct Answer: D.**