Background: Cytochrome p450 (CYP) 1A2 gene polymorphisms are thought to be involved in theophylline metabolism.
Objective: We analyzed the effect of genetic polymorphisms in the 5'-flanking region to the first intron of the CYP1A2 gene on theophylline metabolism in 75 Japanese patients with asthma and 159 healthy Japanese volunteers.
Methods: Genetic polymorphisms were detected at 4 sites of the CYP1A2 gene, -2964(G/A) and -1569(T/del) in the 5'-flanking region and 155(T/G) and 731(A/C) in the first intron.
Results: There were no significant differences in the distribution of gene polymorphisms between the asthmatic and control groups. Among asthmatic patients, theophylline clearance was significantly lower in patients with the polymorphism at site -2964(G/A) whose genotype was G/A (0.029 +/- 0.001 L x h(-1) x kg(-1)) or A/A (0.029 +/- 0.002 L x h(-1) x kg(-1)) than in those whose genotype was G/G (0.034 +/- 0.001 L x h(-1) x kg(-1)) (P <.01 and P <.05, respectively). High theophylline clearance levels significantly correlated with age in the G/G subgroup of site -2964(G/A) (P <.05, r = -0.35) but not in the G/A or A/A subgroup.
Conclusion: Given its potential side effects, theophylline may need to be used with care in patients with the A allele at site -2964(G/A) in the CYP1A2 gene, because theophylline metabolism levels are lower in such patients, particularly in young asthmatic individuals.