13.2 : 鎮痛と疼痛管理

Pain, a complex neurochemical response to harmful stimuli, is central to numerous clinical pathologies and can present in acute or chronic forms.

Analgesia, the alleviation of pain, is accomplished through analgesics. Nonopioid analgesics effectively address mild to moderate nociceptive pain, while opioids manage severe or chronic pain conditions.

Opioids encompass opium-derived opiates, endogenous opioids, and their synthetic analogs.

These drugs operate on G protein-coupled opioid receptors, predominantly μ-receptors, which are associated with polymodal nociceptors. These receptors modulate ion channels, neurotransmission, and protein phosphorylation.

Opioids induce analgesia by directly blocking pain transmission terminals, stimulating descending inhibitory pathway neurons, and modulating pain signals.

However, prolonged opioid receptor activation can lead to desensitization, tolerance, dependence, and addiction.

Even therapeutic doses of opioids can cause tolerance and dependence via persistent μ receptor activation.

As a result, opioid use is now closely regulated due to misuse and addiction risks.