Naloxone increases blood flow in the human hand

Area of Science:

• Pharmacology
• Physiology
• Vascular Biology

Background:

• Endogenous opioids play a role in regulating physiological processes.
• The control mechanisms for skin blood flow, particularly in the extremities, are not fully understood.
• Opioid antagonists like naloxone can block the effects of endogenous opioids.

Purpose of the Study:

• To investigate the effect of naloxone on peripheral skin blood flow and temperature.
• To explore the potential role of endogenous opioids in regulating hand blood flow.
• To assess the therapeutic potential of opioid antagonists for circulatory disorders.

Main Methods:

• Intravenous administration of naloxone (2 mg and 0.4 mg) to healthy volunteers.
• Measurement of finger and hand blood flow and skin temperature.
• Intradermal injections of naloxone and morphine to assess local skin reactions and histamine release.

Main Results:

• Intravenous naloxone caused a marked increase in hand blood flow and skin temperature in 70% of subjects.
• The response to naloxone was dose-dependent, with a lower dose producing a smaller and briefer effect.
• No local skin reactions were observed with naloxone alone, ruling out histamine release as the cause of increased blood flow.

Conclusions:

• Hand skin blood flow appears to be under endogenous opioid control in a subset of individuals.
• Opioid antagonists may represent a novel therapeutic strategy for conditions characterized by impaired skin blood flow, such as Raynaud's disease.