All of the following are true about opioids except?
**Core Concept**
Opioids are a class of medications used to treat moderate to severe pain by interacting with opioid receptors in the central nervous system. They work by activating these receptors, leading to a decrease in pain perception and a feeling of euphoria.
**Why the Correct Answer is Right**
Opioids bind to mu (μ), kappa (κ), and delta (δ) opioid receptors in the brain and spinal cord. Mu receptors are primarily responsible for the analgesic and euphoric effects of opioids. Activation of mu receptors inhibits the release of pain neurotransmitters, such as substance P and glutamate, and increases the release of enkephalins and endorphins, which are natural pain-relievers.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because opioid-induced respiratory depression is a well-known side effect of opioids, particularly when used in high doses or in combination with other central nervous system depressants.
**Option B:** This option is incorrect because tolerance to opioids can develop over time, requiring an increase in dosage to achieve the same level of pain relief. However, this does not necessarily mean that opioids are ineffective.
**Option C:** This option is incorrect because withdrawal symptoms from opioids can occur when the medication is abruptly discontinued or reduced in dosage.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that opioids should be used with caution in patients with a history of substance abuse or those taking other central nervous system depressants, as this can increase the risk of respiratory depression and overdose.
**Correct Answer: A. Opioid-induced respiratory depression is a well-known side effect of opioids.**