Barbiturates and lung cancer in humans.

In a hypothesis-generating study looking for possible carcinogenic effects of drugs in humans, each of three barbiturates (pentobarbital sodium, phenobarbital, and secobarbital sodium) showed a statistically significant association with the subsequent development of lung cancer, with relative risks ranging from 1.5 to 2.8. Further analysis showed that the association was not explained by the increased prescription of barbiturate drugs shortly before the diagnosis of lung cancer or by an association of barbiturate use with cigarette smoking. Much of the data did not support a causal relationship. Neither a relation of lung cancer to duration or intensity of use not one between barbiturate use and a specific histologic type could be demonstrated.