Top 10 medical myths, busted

Hospitalists should be a little more tentative about these tenets.


Despite the rigors of evidence-based medicine, some ill-informed medical axioms die hard.

“There aren't too many things that are pure myths in medicine, but there are definitely things that we were taught that were pure dogma,” said Douglas S. Paauw, MD, MACP, in April at Internal Medicine Meeting 2019.

Photo by Kevin Berne
Photo by Kevin Berne

Medical myths persist for many reasons, including physiologic assumptions, case reports, and tradition, he said. This last one in particular has a strong hold on practice. “Tradition is very powerful, and remember, it's only really in the last 100 years or so that we've really had a strong attempt to have strong evidence for things,” said Dr. Paauw, professor of medicine at the University of Washington School of Medicine in Seattle.

During his talk, “Busting Medical Myths: When Dogma Is for the Dogs,” he debunked many common medical misconceptions. Below are 10 of the top tenets hospitalists may want to be more tentative about.

Myth No. 1: Never give epinephrine in the fingers or toes. “What we've always been taught is, don't give epinephrine in any end-arterial field because it could cause ischemia. . . . I made the mistake of grabbing a bottle of lidocaine with epi when I was a medical student to numb somebody up with a hand [laceration], and boy did I hear it,” said Dr. Paauw. But these concerns don't bear out in the literature.

A review of 39 studies of epinephrine digital blocks in the fingers and toes found that there were no cases of digital necrosis or gangrene in any patient, according to results published in the November 2015 Journal of Emergency Medicine. Dr. Paauw added that hand surgeons and podiatrists routinely use epinephrine injections and that case reports of massive doses of epinephrine injection into the hand have shown no ischemia or major problems. “Bottom line is, this appears to be extremely safe and may be helpful,” at least in the fingers and toes (the jury is still out on other areas, such as the ears and genitalia), he said.

Myth No. 2: Docusate is the go-to treatment for constipation. “It is still one of most commonly used drugs for constipation, especially on the surgery side when people are discharged on narcotics . . . but it probably doesn't do much in the way of softening stool,” said Dr. Paauw. One systematic review, published in the February 2000 Journal of Pain and Symptom Management, concluded that the drug's use in palliative care has been based on inadequate experimental evidence.

More recently, the Canadian Agency for Drugs and Technologies in Health concluded in June 2014 that “[T]he available evidence suggests that docusate is no more effective than placebo in the prevention or management of constipation.” Dr. Paauw recommended sticking to constipation treatments that have “some real efficacy,” such as psyllium and polyethylene glycol.

Myth No. 3: Metronidazole and alcohol don't mix. For years, physicians have told patients that they might get a disulfiram-like reaction if they combine alcohol with metronidazole, Dr. Paauw noted. “On every pill bottle of metronidazole you prescribe, there's a little martini glass with a slash through it,” he said. This myth mainly comes from case reports. “A theory that this reaction occurred was in many of the pharmacology textbooks from the '50s and '60s, and so the case reports followed,” said Dr. Paauw.

One review, published in the February 2000 Annals of Pharmacotherapy, analyzed six case reports from 1969 to 1982 that allegedly showed this reaction and found that none produced any evidence that it exists. Four of eight patients in the reports had serious adverse events, including one death. However, “They didn't have evidence of increased acetaldehyde levels . . . and then the death, they didn't even have a prescription for metronidazole. They did some bloodwork and they said, ‘We found evidence of metronidazole in the bloodstream,’ but there are many drugs that cross-react with metronidazole,” he noted.

With the case reports potentially in question, Dr. Paauw looked for other data and found a study in rats that showed increased intracolonic (but not blood) acetaldehyde levels with ethanol and metronidazole. “So what do we need? A human study. Where do you get volunteers? Medical school,” he said. A double-blind trial randomized 12 healthy medical students to receive alcohol plus either placebo or metronidazole three times a day for five days. There was no difference between groups in blood acetaldehyde levels, vital signs, or symptoms, according to results published in the June 2002 Annals of Pharmacotherapy.

“For healthy adults, we have a small study that it seemed to be OK,” Dr. Paauw concluded. “But we don't know what the deal is with most of the people we take care of,” such as patients with renal disease or end-stage liver disease, who could have problems with just the alcohol alone. “Certainly [if] the issue comes up for the young healthy adult, I think the risk is very, very low,” he said.

Myth No. 4: Iron must be dosed multiple times a day to treat iron deficiency. “I was certainly taught to give iron three times a day, and that was certainly what the tagline was in the 1980s, and that continued through the '90s,” said Dr. Paauw. As an attending in 2000 with the thought that three-times-daily dosing might be overkill, he challenged his trainees to an experiment: Take iron three times a day for a week. An intern was done with it in one day, a resident lasted two days, Dr. Paauw lasted three days, and one medical student with an iron will lasted five days.

In terms of the data, he said, one of the best studies on once-daily iron was published in the October 2005 American Journal of Medicine and randomized 90 hospitalized elderly patients with iron-deficiency anemia to receive elemental iron as 15 mg or 50 mg of liquid ferrous gluconate, or 150 mg of ferrous calcium citrate. At 60 days, there was no difference between groups in the rise of hemoglobin or ferritin levels, but there was a significant difference in side effects, with fewer patients in the low-dose group reporting abdominal discomfort compared to the other groups. In addition, some newer data suggest that dosing iron every other day might lead to better absorption, Dr. Paauw noted.

Myth No. 5: Morphine, oxygen, nitroglycerine, and aspirin (MONA) should be routinely given to patients with acute coronary syndrome or suspected myocardial infarction (MI). While oxygen is widely used in these patients, a December 2016 Cochrane review found that it did not significantly reduce all-cause mortality or recurrent MI. In addition, a randomized trial published in September 2017 by the New England Journal of Medicine found that routine use of supplemental oxygen in 6,629 patients with suspected MI (but not hypoxemia) did not reduce one-year all-cause mortality.

So when it comes to putting everyone with suspected MI on oxygen, “That train has left the station,” said Dr. Paauw. “A lot of the articles I quote here are from many years ago, and . . . it always amazes me that . . . we continue to do things. But this one really has seemed to change practice quite a bit.”

The morphine component is less certain. “There are studies that show worse outcomes in patients who were given morphine and actually increased infarct size, but there are also studies that refute that,” he said. A reasonable approach is to treat patients with chest pain with aspirin and, if blood pressure allows, nitrates or beta-blockers, adding morphine if pain persists, said Dr. Paauw. “We don't need to give oxygen in patients with [saturations] over 90%.”

Myth No. 6: Medications are no good past their expiration date. The expiration date is the date when the manufacturer still guarantees 90% potency, and companies have very little motivation to extend it, Dr. Paauw explained. One group that does have a vested interest in doing so is the U.S. military. An analysis of data from the federal Shelf Life Extension Program, published in May 2006 by the Journal of Pharmaceutical Sciences, found that 88% of 122 drugs from 3,005 lots had 90% or more potency one year past the expiration date, with an average extension of more than five years.

Another study, published in November 2012 by Archives of Internal Medicine, assessed medications (mostly compound drugs) that were sealed in boxes and had expired 28 to 40 years prior. Overall, 12 of 14 compounds had retained 90% or more potency, and medications that stood the test of time included codeine, hydrocodone, and acetaminophen. “The only one that broke down was aspirin. The aspirin was only at 1% of what was supposed to be in it,” said Dr. Paauw.

One medication of extra financial and safety-related importance is epinephrine injection, which was found to be sterile and detectably pure more than 2.5 years after expiration in a study published in January 2018 by Prehospital Emergency Care. Another study of 40 EpiPens that were one to 50 months past expiration found that all had 80% or more of their labeled concentrations, according to results published in June 2017 by Annals of Internal Medicine. But because of the high morbidity of a failed injection, Dr. Paauw said this is not enough information to rely on expired pens (the pens will not cause toxicity, but they may be ineffective). Nonetheless, he recalled a patient who did not use epinephrine when needed and proceeded to get very sick. “When I asked why, they said because it had expired,” Dr. Paauw said, adding that he tells patients to keep expired pens as backup. “It's better to have something there than nothing.”

Myth No. 7: Vitamin B12 injections are necessary to treat pernicious anemia. This myth comes from studies in the '40s and '50s that gave tiny doses of oral B12 with animal intrinsic factor based on the idea that intrinsic factor was necessary for absorption, Dr. Paauw said. However, there's a second physiologic mechanism at play with bigger doses (e.g., 1,000 µg), mass action, which allows B12 to cross into the bloodstream, he explained. “That was not known with these early studies . . . so these all failed because they got antibodies and they gave tiny doses, so it was ‘proven’ that oral treatment didn't work,” Dr. Paauw said.

Now, low-quality evidence shows that oral and intramuscular B12 have similar effects in terms of normalizing serum B12 levels, but oral B12 costs less, a March 2018 Cochrane review concluded. “They graded it low-quality because of the numbers,” as the available studies on daily dosing were small, Dr. Paauw noted. “We don't have a huge study, but it works, and it's a lot easier for patients to take oral B12.”

Myth No. 8: Beta-blockers increase the risk of depression. This myth comes from a case series published in 1967 in which the major symptom reported was fatigue, Dr. Paauw said. “We do know that beta-blockers can be associated with fatigue,” he said, but everyone latched onto the idea that the association with depression was a strong one.

Several studies have failed to find a powerful association. Most recently, a propensity-matched study in the April 2016 American Heart Journal found that beta-blocker therapy was not associated with an increase in depressive symptoms up to 12 months after acute MI. “I think it's still controversial, but if an effect exists, it's small, and certainly it shouldn't stop us from using beta-blockers when the beta-blocker indication is really a strong one,” Dr. Paauw concluded.

Myth No. 9: Do not perform a lumbar puncture in a patient with suspected meningitis before clearing with imaging. “There was a huge push in the '80s and '90s for clearing everybody with a CT before we did a lumbar puncture for suspected meningitis, and that . . . became kind of the standard thing,” but there are no strong supporting data for this practice, he said.

Older studies have shown that bad outcomes are rare in patients with documented intracranial mass lesions or brain tumors who received lumbar punctures, Dr. Paauw noted. “I'm not recommending that we do lumbar punctures in these people, but this looked at what type of risk we're looking at. . . . In patients where time is of the essence, we need to be making diagnoses and getting them treated rapidly if worried about meningitis,” he said.

Myth No. 10: Avoid narcotics before surgical evaluation for acute abdominal pain. “What I was taught was the surgeons are going to kill you if you give narcotics because you're going to mess their exam up and they won't be able to do their job,” said Dr. Paauw. “Sometimes patients had to wait for a while, and they'd be in terrible pain and they'd be writhing around.” Fortunately, this myth is all but retired, he said.

One study of 100 patients randomized half to receive intramuscular narcotics and half to receive intramuscular saline, and surgeons felt equally confident in diagnostic and management decisions in both groups, according to results published in September 1992 by The BMJ. Plus, the decision to operate or observe was incorrect in two patients in the narcotic group and nine patients in the saline group. “This actually suggested maybe they did a little better when the patient was more comfortable. Maybe they could get a little bit better exam,” said Dr. Paauw.