A drug commonly prescribed to ease the nausea of morning sickness may not be as effective as once believed, a new analysis suggests.
The drug is called Diclectin, a combination of vitamin B6 and a common antihistamine, and is recommended as a treatment for women suffering from nausea and vomiting during pregnancy. Canadian doctors write 300,000 prescriptions for Diclectin every year.
Yet when Toronto family doctor Nav Persaud reanalyzed the original data from a 2009 manufacturer-funded clinical trial, he could find no evidence the pill was effective. In fact, Persaud discovered the pill fell short of drug company Duchesnay’s own pre-established threshold.
“I have completely stopped prescribing this medication. I don’t think it should be prescribed. I don’t think patients should take it.” Persaud said.
His research on Diclectin started with a patient’s question: Does this pill work? With prescription pad in hand, Persaud realized he didn’t know, even though he’d been taught to give Diclectin to pregnant women if they were experiencing nausea and vomiting.
“I had been routinely prescribing the medication without thinking about it.”
When he checked the scientific literature, he couldn’t find data on Diclectin’s efficacy. So he made what he assumed would be a routine request to Health Canada for the information the agency has about the drug.
“If I’m a doctor who prescribes this medication, obviously Health Canada is just going to show me all the information about the clinical effect,” Persaud said.
He was wrong. The information was considered confidential business information and Health Canada refused to release it. That was in 2011.
7-year fight for data
For the next seven years Persaud filed access to information requests to both the U.S. Food and Drug Administration (FDA) and Health Canada with little success. But after Vanessa’s Law (Protecting Canadians from Unsafe Drugs Act) was passed in 2014, Health Canada agreed to show him the manufacturer’s 2009 trial data. But only after requiring him to sign a confidentiality agreement promising to destroy the documents.
As he sifted through the thousands of pages, he realized the company did not meet its own standard of proof. In the original study plan, it was decided the drug needed to show an improvement of three points on a symptom scale. But in the end, the difference between the drug and the placebo was less than one point — falling far short of the company’s target.
“So it’s clear the results of the study indicate the medication is not effective,” Persaud said.