Serum and urine levels of phenol following phenol blocks

In 20 patients with chronic peripheral vascular disease measurement was made of serum and urine phenol concentrations after lumbar or thoracic sympathetic block with 4-10 ml of seven per cent aqueous phenol. Peak concentration times (tmax), peak concentrations (Cmax), lag times (Tlag), apparent elimination half-lives (t1/2el), and areas under the serum concentration curves (AUC) were determined. The values of tmax, Cmax, Tlag, t1/2el, and AUC were 18.8 +/- 2.5 min, 3.01 +/- 0.28 microgram X ml-1, 5.3 +/- 1.6 min, 30.3 +/- 2.8 min, and 365 +/- 41 micrograms X ml-1 X min-1, respectively, for unconjugated phenol. Values for conjugated phenol were 54.9 +/- 4.5 min, 4.15 +/- 0.25 microgram X ml-1, 9.9 +/- 5.9 min, 64.0 +/- 7.3 min, and 838 +/- 95 micrograms X ml-1 X min-1, respectively. The cumulative urinary excretion in the conjugated form within 8 h ranged from 31 to 63 per cent of the dose administered. The results indicate that phenol has a very short half-life and is excreted quickly into the urine, conjugated with sulfate.