Excretion of metabolites is via the kidneys. Phenol has systemic side effects including central nervous system stimulation, cardiovascular depression, nausea, and vomiting. Systemic doses of more than 5 grams can cause convulsive seizures and central nervous system depression. Doses less than 100 mg are less likely to cause serious side effects. It was first used as a neurolytic agent in 1936 by Putnam and Hampton.
Phenol causes nerve destruction by inducing protein precipitation.
There is loss of cellular fatty elements, separation of the myelin sheath from the axon, and axonal edema. However, phenol is not as effective as alcohol at destroying the nerve cell body and its blocking effect tends to be less profound and of shorter duration than alcohol. At a concentration of 2-3 percent in saline, phenol seems to spare motor function. The efficacy of 3 percent phenol in saline is comparable to that of 40 percent alcohol. It has an immediate local anesthetic effect due to its immediate selective effect on smaller nerve fibers.