Chantix, Heparin Top List of Adverse Events

Oct 29, 2008
By Pharmaceutical Executive Editors

Pfizer’s smoking-cessation drug, Chantix, received more reports of adverse reactions in the first quarter of 2008 than any other branded drug, according to a new report by The Institute for Safe Medication Practices (ISMP).

The non-profit group analyzed and compiled every report submitted to FDA during the first three months of the year. The research found 20,745 reports of serious injury from prescription drugs in the United States, a 34 percent spike compared with last year’s quarterly average. Even more curious, instances of death increased from 1,868 to 4,824 over the previous quarter.

But according to Thomas Moore, senior scientist at ISMP, the more we know, the more we know we don’t know. “We don’t know whether we are gaining or losing ground in drug safety,” he told Pharm Exec. “[Until now] we didn’t know which drugs were responsible for serious adverse events, and without some basic data, it was difficult to develop rational strategies to manage those risks better.”

ISMP combed through FDA’s adverse report updates and selected only those that have primary health significance for the U.S. population, weeding out foreign reports, non-serious events, events that appeared in studies, and reports submitted by lawyers.

Topping the list of offenders was Chantix (varenicline), with 1,001 reports of serious injury reported to the federal agency—more than the total number reported for all other branded drugs combined. 

The top five drugs associated with serious injury reports:

  1. varenicline (1,001)
  2. heparin (779)
  3. fentanyl (631)
  4. interferon beta (582)

“The increase was the largest we’ve seen in looking at various quarters,” Moore said. “The two leading drugs—Chantix and heparin—were not unexpected as both have been heavily publicly reported [in the news].”

Blood thinner heparin had a tough year. Sophisticated contamination with a copycat ingredient upstream of the Chinese manufacturer led to a global recall of many versions of the generic. The medication received adverse reports from batches made by different manufacturers. “Baxter Healthcare had the largest recall of the drug and accounts for the largest share of adverse event reports we see,” Moore said. “The effect was striking: There was normally 40 reports per quarter [for heparin], and that number went up to more than 100.”

Fentanyl is a Schedule II opioid painkiller many times more powerful than morphine and widely sold on the black market. Interferon beta is a multiple sclerosis drug marketed under three different brand names; its potent anti-inflammatory effects cause a high rate of side effects, most commonly a chronic flu-like syndrome.

Both Chantix and heparin have been high-profile, not to say sensational, stories in the media since last year. Pfizer’s carefully planned rollout of the breakthrough nicotine-receptor partial antagonist was partially derailed by growing reports of suicidality, bizarre dreams, aggressive and other impulsive behavior, and other side effects. The drug giant was at pains to defend its blockbuster-to-be, arguing that the adverse events may have been symptoms of nicotine withdrawal. But a backlash against the drug has resulted in flagging sales.

It’s hard to overlook the fact that the two drugs that triggered the most reports from consumers are also the ones that got the most bad press. While the numbers reported in the study are factual, it’s next to impossible to prove that Chantix and heparin actually caused the most side effects. FDA also can’t guarantee that reports are truthful when listing whether the drug was taken with anything else.

“We state in the report that publicity was probably an element in the volume of Chantix reports, and there is no question that that contributed to it,” Moore said. “With extremely rare exceptions, it just means that a larger fraction of the events are being reported.”

Pfizer could not be reached for comment by deadline, but a spokesperson got back to us on October 30 with these comments- now posted on the Pharm Exec blog.

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