Nicotine and cotinine concentrations in serum and milk of nursing smokers.

Abstract

Analysis of 44 milk samples from 23 nursing smokers revealed that there was a linear correlation between nicotine concentrations in serum and in milk (r = 0.70). The nicotine concentrations in milk were considerably higher than the corresponding serum concentrations: milk/serum concentration ratio = 2.92 +/‐ 1.09; (n = 44). There was also a linear correlation between the cotinine concentrations in serum and in milk (r = 0.89). The cotinine concentrations in milk were lower than the corresponding serum concentrations: milk/serum concentration ratio = 0.78 +/‐ 0.19; (n = 44). The direct comparison between the half‐ lives of nicotine in serum and in milk was possible in five nursing smokers. The half‐life of nicotine in milk was determined in four additional smoking mothers. The half‐life of nicotine in milk t 1/2 = 97 +/‐ 20 min slightly exceeded the half‐life of nicotine in serum t 1/2 = 81 +/‐ 9 min; the difference between these two values was not statistically significant (P greater than 0.05). Cotinine concentrations remained fairly consistent during a 4 h interval without smoking. 1984 The British Pharmacological Society