It attenuates "second pain" with primary effects on slow-conducting, unmyelintated C-fibers and is less effective on neuropathic pain and "first pain" signals through small, myelinated A-fibers.Fentanyl can produce the following clinical effects strongly, through μ-receptor agonism. Supraspinal analgesia (μ1)
Respiratory depression (μ2)
Physical dependence
Muscle rigidityIt produces sedation and spinal analgesia through Κ-receptor agonism. Therapeutic effects
Pain relief: Primarily, fentanyl provides the relief of pain by acting on the brain and spinal μ-receptors. Sedation: Fentanyl produces sleep and drowsiness, as the dosage is increased, and can produce the δ-waves often seen in natural sleep on electroencephalogram. Suppression of the cough reflex: Fentanyl can decrease the struggle against an endotracheal tube and excessive coughing by decreasing the cough reflex, becoming useful when intubating people who are awake and have compromised airways. After receiving a bolus dose of fentanyl, people can also experience paradoxical coughing, which is a phenomenon that is not well understood. Detection in biological fluids
Fentanyl may be measured in blood or urine to monitor for abuse, confirm a diagnosis of poisoning, or assist in a medicolegal death investigation. Commercially available immunoassays are often used as initial screening tests, but chromatographic techniques are generally used for confirmation and quantitation. The Marquis Color test may also be used to detect the presence of fentanyl. Using formaldehyde and sulfuric acid, the solution will turn purple when introduced to opium drugs.
Dyschromatosis universalis hereditaria is a rare genodermatosis characterized by reticulate hyper- and hypo- pigmentated macules in a generalized distribution. : 856 Both autosomal dominant and recessive inheritance have been reported with the disorder.It has been associated with mutations in genes SASH1 and ABCB6. References
External links

Dyschromatosis universalis hereditaria: Two cases, Dermatology Online Journal.