Effect of pH and urine flow on urinary nicotine excretion after smoking cigarettes.

Effects of pH and urine flow on urinary excretion of nicotine were examined in 11 smokers after they had smoked 3 cigarettes during water diuresis. Plasma nicotine showed a slight but nonsignificant rise after smoking. Urinary excretion of nicotine increased significantly from the pre-smoking levels of 258 +/- 76 and 252 +/- 147 (mean +/- SEM) ng/15 min to the peaks of 2,587 +/- 1,224 and 2.561 +/- 584 ng/15 min 30 and 45 min after the start of smoking. Thereafter, urinary nicotine tended to decrease and rise with changes in urinary flow. There was a correlation between urinary nicotine and urinary flow after smoking (r = 0.26, p less than 0.05). Eleven subjects were grouped based on the mean urinary pH throughout the experiment. No significant amount of nicotine was excreted in the group with pH above 7.5 while groups with pH below 7.4 excreted substantial nicotine after smoking. There was a negative correlation between urinary pH and nicotine excretion (r = -0.58, p less than 0.001). Urinary excretion of nicotine cannot be used as an index of smoking unless pH and urine flow are controlled.