Oxymorphone HCl (Opana) for the Relief: PATHOPHYSIOLOGY OF PAIN

Posted by James

The most common type of pain is nociceptive. Clinically, pain can be classified as “nociceptive” if it can be determined that the pain is related to the degree of receptor stimulation by processes that cause tissue injury. Potential causes of the tissue injury include a cut, bruise, bone fracture, crush injury, a burn, or cancer.

Nociceptive pain involves the activation of peripheral pain receptors (nociceptors) by active tissue damage or noxious stimuli and includes somatic and visceral pain. Somatic pain originates from damage to the skin, muscle, or bone; it presents as an aching, throbbing, stabbing pain, with or without a pressure sensa-tion. Visceral pain results from damage to internal organs; it is characterized by a gnawing, cramping, aching, sharp pain, with or without a stabbing sensation.
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Normal somatosensory processing of pain involves the interaction between afferent systems activated by the tissue injury and the accompanying inflammation. The primary afferent system includes nociceptors (sensory neurons), signal processing in the dorsal horn of the spinal cord, ascending neural pathways, and thalamic and other specialized brain structures.⁵ Peripheral nociceptors are located in the skin, muscle, joints, and some visceral tissues.

In the pathophysiology of nociceptive pain, nociception consists of four steps:

1.  The process begins with trans-duction (depolarization), which is the response of peripheral nociceptors to noxious stimuli.

2.  Transmission is the process by which the stimuli proceed along the primary afferent nociceptive axons to the spinal cord and then on to the brain.

3.  After the impulses reach the brain, they are intellectually recognized by the patient as pain in the process known as perception.

4.  The final process is modulation, in which nociceptive impulses are inhibited. Pain modulation is determined by activity in the endorphinergic system and other pain-modulating systems.

In the endorphinergic system, pain relief is mediated by the binding of endogenous opioid compounds to the subset of mu, delta, and kappa recep-tors. Endorphins are widely distributed in the body and are closely related to systems that regulate homeostasis, response to stress, and pain.