The rate of procaine hydrolysis in serum of normal subjects and diseased patients

The drug metabolism pathway of ester hydrolysis was studied by measuring the rate of procaine disappearance from unmodified serum samples incubated at 37° C. Serum pseudocholinesterase appears to be the enzyme catalyzing this hydrolysis. Healthy adults had a mean serum procaine half‐life of 0.66 ± 0.14 minutes. Sera from newborn infants (cord blood), adults with liver disease, and adults with impaired renal function hydrolyzed procaine more slowly than did sera from healthy adults. Mean half‐lifes for these groups were: 1.40 ± 0.5 minutes, 2.3 ± 0.9 minutes, and 1.40 ± 0.83 minutes, respectively. The degree of slowing of procaine hydrolysis in sera from patients with impaired renal function was proportional to the patients' blood urea nitrogen values. The mechanism for this slowed hydrolysis in sera from uremic patients is decreased levels of enzyme activity and not competitive enzyme inhibition by some substance in the serum.