[Influence of tobacco on the serum levels and pharmacokinetics of phenylbutazone and oxyphenbutazone].

The serum levels of a number of drugs are reduced by smoking. The authors wanted to see whether this phenomenon occurred with phenylbutazone. With this objective, they compared the changes in serum levels of phenylbutazone and oxyphenbutazone, the hydroxylated metabolite of phenylbutazone, during ten days of administration, in 9 smokers and in 6 non-smokers. Blood samples were taken every day at 8:00 a.m. and the PB and OPB were assayed by high performance liquid chromatography. The comparison of the mean serum levels of PB in smokers and non-smokers revealed a statistically significant reduction (p less than or equal to 0.05) of this level in the smoker, between D5 and D10. Comparison of the mean serum levels of OPB in smokers and non-smokers revealed a statistically significant reduction of this level in the smoker, but only on days 9 and 10. When we compare these results with those reported in the literature for other drugs, it would appear that tobacco smoke accelerates the metabolism of phenylbutazone and oxyphenbutazone by a mechanism of enzyme induction. It is proposed that the therapeutic activity of phenylbutazone is reduced in the smoker, but this has not been confirmed by a reliable clinical evaluation in this initial study.