Phenobarbital use and bladder cancer risk

Two epidemiologic studies have reported an inverse association between use of phenobarbital (PB) and bladder cancer development. It was proposed that PB use protects against bladder cancer by inducing enzymes that participate in the detoxification of human bladder carcinogens, such as the aminobiphenyls and naphthylamines, which are found in cigarette smoke.

A population-based case-control study was conducted in Los Angeles, California, involving 815 incident bladder cancer cases and an equal number of controls who were matched to the index cases by neighborhood, sex, date of birth (within 5 years), and race. Detailed information on lifetime use of PB was collected through in-person interviews.

Ever use (20 or more times over lifetime) of PB was not associated with risk of bladder cancer (OR: 0.86; 95% CI: 0.54, 1.39). Regular use of PB also was not associated with risk of bladder cancer in either men or women, in either smokers or non-smokers, although the number of regular users in cases and controls were relatively small (21 cases vs. 15 controls, OR: 1.20; 95% CI: 0.59, 2.45). In fact, compared with non-users, subjects in the highest category of lifetime PB consumption were at a non-significant 2.46-fold increased risk of bladder cancer (95% CI: 0.90, 6.78).

The present study did not observe a protective role of PB use in bladder cancer development in the general population.