Decreased theophylline half-life in cigarette smokers.

In a group of 19 hospitalized patients, most of whom smoked, the half-life of theophylline following an I.V. aminophylline bolus was 3.6 ± 1.5 hours. When the young male control group was broken down by smoking history, 10 smokers had a theophylline half-life of 4.1 ± 1.2 hours, and 14 non-smokers a theophylline half-life of 7.2 ± 1.8 hours. The prolongation of half-life in the non-smokers was very significant (p<0.0001). These findings are consistent with observations that polycyclic hydrocarbons are strong inducers of microsomal enzymes involved in drug metabolism, and may help explain the individual variations of theophylline half-life.