Drug companies are misleading doctors by withholding important information about the effectiveness of their products, says epidemiologist Dr. Ben Goldacre.

In his new book, Bad Pharma, Goldacre points out flaws reported in medical literature in the way drugs are tested and approved for use and illustrates some of the deadly consequences.

The biggest problem, he says, is that only half of all clinical trials are published, and often the trials that are not published are the ones showing the drug is ineffective.

"If you withhold half of the results of all the clinical trials that are conducted, then you … pollute the well of evidence that all of us use to make decisions,” he told CBC's The Current.

"And that means that nobody can know which treatment is best."

Goldacre outlined a couple of examples, including one case in which 100,000 people may have died prematurely because the results of an early trial were never shared in the academic literature.

Testing against a placebo

Another way in which drug approvals are flawed, Goldacre said, is that they allow drug companies to test against a placebo instead of the best possible existing treatment.

"If you don't get the best treatment, then as far as you're concerned as a patient, then I think you’ve been failed."

Goldacre also discussed problems with the way clinical trials are designed and run.

Many of the problems with drug testing and approvals have long been known and discussed in the academic literature, Goldacre said. But he thinks the discussion should also be shared with the public.

"Some of these problems have been documented for three decades," he added, "and we've failed as a profession to fix them."