Opioids Agonists and Antagonists in Medicine

Morphine is the primary alkaloid found in crude opium.

Opioid refers to any substance, whether from within the body (endogenous) or from outside (exogenous), that has effects similar to morphine.

Methadone is categorized as a strong opioid agonist, meaning it binds strongly to opioid receptors to produce a significant effect.

Opioids interact with mu (μ), kappa (κ), and delta (δ) receptor subtypes, each with varying degrees of potency. These interactions mediate different effects such as analgesia, sedation, and respiratory depression.

Partial agonists are drugs that produce a less than maximal response, even when all receptors are occupied, indicating low intrinsic activity.

The neuroendocrine system, particularly the hypothalamus, is often regulated by certain opioids, influencing hormonal balance.

Higher doses of opioids are a key predictor of opioid-related adverse events, increasing the risk of side effects.

Morphine is associated with decreased renal blood flow (RBF) and enhanced renal tubular sodium (Na+) absorption.

Strong opioid agonists can commonly cause urinary retention and should be used with caution in patients with renal calculi colic.

Sleep apnea is an opioid-related factor that is relevant in the context of chronic obstructive pulmonary disease (COPD).

Naltrexone has a reversal effect that lasts for 48 hours and is used in the treatment of heroin addiction to block the effects of opioids.

The P450 system pathway in opioid metabolism can lead to the formation of potent metabolites for certain drugs, affecting their overall activity and duration.