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Doctors Often Ignore Deadly Drug Interaction Warnings

Millions of Americans swallow five or more pills daily. Doing so dramatically increases the risk of a deadly drug interaction that prescribers may miss.

The news this week about aggressive control of hypertension (see this news article) will doubtless lead to many more prescriptions for blood pressure medicine. As it is, Americans are taking more medicine than ever (JAMA, Nov. 3, 2015). The number of people taking five or more drugs simultaneously has nearly doubled from 8% to 15% in a decade. Many older people are taking far more than that.

When people take that many medicines together, the risk for a dangerous, or even a deadly drug interaction, goes up dramatically. One study revealed that prescribers performed terribly on a test of drug incompatibility (Drug Safety, 2008). The health care professionals classified less than half of the fourteen drug pairs they were tested on correctly. This was a take home test, so they could have looked up the right answers had they been so motivated.

The authors concluded: “This study suggests that prescribers’ knowledge of potential clinically significant DDIs [drug-drug interactions] is generally poor.”

Overriding Deadly Drug Interaction Warnings:

Computerized systems are supposed to alert doctors when a dangerous or a deadly combination has been prescribed to a patient. But another study found that doctors frequently override and ignore the drug interaction alert they may get on their smart phone or computer. The research was carried out at six Veterans Affairs (VA) medical centers (American Journal of Managed Care, Oct., 2007). Over a one-year period there were 291,880 drug-drug interaction alert overrides. Nearly three fourths of the overrides were considered “critical drug-drug interactions.”

We received this message from Nanci in Illinois:

Q. I see a cardiologist, a rheumatologist, have a primary doctor, and none of them ever gives me drug interaction information!! I asked one cardiologist about the side effects and interactions of a new beta blocker he was prescribing. His answer: “I don’t know.”

I changed doctors, but still have to ask. My current heart doc looks up interactions in his desk reference. If I don’t ask, he just writes the script with no instructions. The pharmacist is better and always asks me if I have any questions.

It would be nice if doctors were more knowledgeable about the side effects of the meds they pass out like candy.

I have a friend who is 85 years old and who takes a beta blocker, an ACE inhibitor, a calcium channel blocker (CCB) plus a diuretic at fairly high doses. His blood pressure is quite low. He said he passed out briefly in his garage at one time, but never questions his meds.

Doctors are overworked but they should do a better job of informing their patients of potential drug interactions and side-effects.

A. We agree with you Nanci. In fact it is critical that patients be warned by both physicians and pharmacists about both side effects and drug incompatibilities. Sadly, this does not happen nearly enough. Both pharmacists and physicians override interaction alerts with great regularity.

Is a Deadly Drug Interaction Warning Really Deadly?

Many doctors may override or ignore computer-generated drug interaction warnings because they don’t really think they are all that worrisome. That is a little like playing Russian Roulette with a patient’s life.

A study of 24,849 alerts at primary care practices affiliated with two Harvard teaching hospitals produced shocking results (PLoS One, Dec. 26, 2013):

“We found that, despite extensively modifying our CDS [clinical decision support] system to improve user acceptance and show only the most important alerts, providers continued to override these alerts that are likely to cause serious patient injuries. More needs to be done to effectively [provide] feedback to providers with high inappropriate override rates and improve prescribing safety in the primary care setting.”

The People’s Pharmacy translation of that stuffy medical language is: “we tried to make the deadly drug interaction alerts better and easier to use but doctors kept ignoring them anyway.”

What Are the Consequences of Ignoring a Deadly Drug Interaction Warning?

Canadian researchers have been concerned about a deadly drug interaction linked to a class of blood pressure medicines called RAS (Renin-Angiotensin System) inhibitors. These include the ACE inhibitors Nanci mentioned in her question as well as ARBs (angiotensin receptor blockers). Popular drugs in the RASi class include lisinopril (Prinivil, Zestril) and ramipril (Altace) as well as losartan (Cozaar) and valsartan (Diovan). You can find a more complete list of RAS inhibitors at this link.

When the Canadians combed through their patient database over a 17-year time period they discovered that people who had received either an ACE inhibitor or an ARB blood pressure drug together with co-trimoxazole were more likely to have died within two weeks of receiving the combination compared to people who had received a different kind of antibiotic (penicillin type). Described in BMJ (Oct. 30, 2014).

The investigators concluded that the combination of the co-trimoxazole antibiotic and the blood pressure medicine “increased risk of sudden death in older patients.” They also noted that such deaths were likely to be blamed on underlying heart disease rather than a drug interaction. To read more about this landmark research go to this link.

The Canadian researchers have also demonstrated that a popular diuretic (spironolactone) can also trigger life-threatening complications when it is combined with the same antibiotic (CMAJ, Mar. 3, 2015). Their interpretation:

“The antibiotic trimethoprim-sulfamethoxazole was associated with an increased risk of sudden death among older patients taking spironolactone.”

How Can Patients Protect Themselves from a Deadly Drug Interaction?

In our book, Top Screwups Doctors Make and How to Avoid them, you will find a whole chapter on this crucial subject. You will also discover our list of Top 11 Tips for Preventing Dangerous Drug Interactions. If you know someone who is taking a handful of pills every day, you may want to give him or her a copy of this book. The examples we have provided barely scratch the surface of the deadly drug interaction disaster that is played out every day in this country and around the world. Here is a link to Top Screwups.

Please share your own experience with drug interactions below in the comment section and vote on this article at the top of the page.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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