Do you know the difference between opiates and opioids?

Opiates are drugs directly derived from the opium poppy (Papaver somniferum), such as morphine and codeine. These substances exert their effect by binding to opioid receptors in the body.

Opioids are a broader term encompassing all drugs that act on opioid receptors, regardless of whether they are natural, semi-synthetic, or fully synthetic. Examples of opioids include fentanyl, oxycodone, buprenorphine, and methadone.

There are several types of opioid receptors, the most important of which are μ- (mu), κ- (kappa), and δ- (delta)-receptors. These are found not only in the central nervous system but also in peripheral tissues such as the gut, heart, and peripheral nerves.
– μ-receptors are primarily responsible for analgesia, euphoria, respiratory depression, and addiction.
– κ-receptors contribute, among other things, to spinal analgesia and sedation.
– δ-receptors play a more modulatory role in pain perception and emotional responses.

The broad distribution of opioid receptors explains both the desired pain-relieving effect and many of the clinically relevant side effects, such as constipation, nausea, bradycardia, and altered levels of consciousness.

Opiates and opioids are primarily metabolized in the liver, often via the cytochrome P450 system or through glucuronidation. Several of these substances have active or water-soluble breakdown products that are excreted via the kidneys. This has important clinical implications:
In cases of impaired liver function, metabolism may be slower, increasing the risk of accumulation and toxicity.
In severe kidney failure, active metabolites can build up, particularly with the use of morphine, leading to prolonged effects and an increased risk of respiratory depression.

For these reasons, dose adjustment, opioid selection, and close clinical observation are crucial in patients with reduced liver or kidney function. In acute situations, pain relief must always be weighed against the patient's physiological reserve and risk of side effects.