Blog | Friday, February 13, 2015

Does oseltamivir work and does it have side effects?

The flu season has really gotten into gear now with 46 of our 50 states reporting widespread influenza activity. Influenza is a virus that infects the respiratory tract, causing sore throat, runny nose, fever and cough. Rarely people with the flu will have nausea, vomiting and diarrhea, but this is not “stomach flu,” which is a term some of us use to describe any one of a number of viruses that give us intestinal symptoms. Influenza is the one where you hurt all over, you have a high fever and cold symptoms, then you start coughing and you can barely get out of bed for days. Sometimes it's milder than that, but it can also be more severe, affecting brain function and sometimes requiring oxygen or life support with a ventilator. It also kills people, on the order of about a half a million worldwide every year, either directly by the destructive effects of the virus or by setting the stage for a devastating bacterial pneumonia.

Flu is very contagious. A person with the flu can spread it to others for 1-2 weeks, and it frequently runs through whole schools, resulting in as many as 1 in 3 children being absent from classes. The very best way to reduce the spread of flu is to have people with the flu stay away from people without the flu. Hand washing is also good. Epidemic flu usually lasts for about 13 weeks each year, tapering off toward the end of the season, and usually it's pretty much gone by March. This year we are starting with influenza A, which is usually the most severe type, and the genetic signature is not one that is well covered by the present flu vaccine.

The Centers for Disease Control (CDC) posted an article detailing the present flu situation. They estimate that the vaccine is 23% effective, but that is based on an odds ratio calculated by comparing a group of sick people who did or did not have the flu when tested and looking at whether or not they were vaccinated. What they mean is that if you are sick enough to be tested for the flu, you are 23% less likely to actually have the influenza virus if you got the vaccination. But the vaccine is still recommended because there will be influenza B coming around later, as well as the non-seasonal flu, H1N1, which should be covered by the vaccine. There is also a chance that the influenza A you are exposed to could be one that has not genetically drifted, which might mean the vaccine would make you more immune to it.

This year's flu is a pretty nasty one, with many people getting sick enough to need hospitalization. It is not the most terrible we have seen, and is similar in how sick it makes people to the 2012-2013 season, 2 years ago. Because the vaccine is less effective this year, though, the CDC is recommending that physicians be very generous about prescribing 1 of the 2 influenza antiviral medications. These are oseltamivir (Tamiflu) and zanamivir (Relenza). Oseltamivir (which is not available as a generic) is a capsule or liquid which is dosed twice daily and costs a bit over $100 for a 5 day course. Zanamivir (also still on patent) costs a little less and is inhaled, twice daily, and is contraindicated in asthmatics since it can make them wheeze. The Cochrane Collaboration, an organization which reviews scientific data in an unbiased fashion, says that neither drug does much for healthy people infected with the influenza virus, and there is no really good data to determine if it helps people who aren't otherwise healthy or who are desperately ill with it. They both tend to make the symptoms a little less severe and shorten the duration of illness by half a day to 1 day. I have been prescribing them generously for years to my patients with the flu, since I know how nasty it is and have always figured that they could use all the help they could get.

A few days ago a friend asked me if I had heard anything about mental effects of Tamiflu. She said that an acquaintance of hers had a son who had committed suicide after being started on it. His girlfriend had just left him, but he was a very psychologically stable person, and this wasn't like him. She said that she had heard that the drug could make people mentally unstable. I thought that it sounded like hogwash, so I checked my handy dandy iPhone Epocrates app and found that behavioral effects and self-injury were quite high on the list of serious side effects. Today, I looked further into it and found that in Japan, where Tamiflu is used more commonly than in the U.S., they reported quite a few cases of psychological side effects, including delirium, primarily in children and adolescents within the first 48 hours that they took the drug, with something like 70 deaths. The Food and Drug Administration reviewed side effects, especially during the 2009 pandemic when Tamiflu was widely used, and found that there were some psychological side effects reported, but pretty rarely. There were also some severe skin reactions, even resulting in death. There were more case reports, including a girl who had manic depressive symptoms that resolved only after a few months, out of South Korea. Tamiflu also makes about 1 in 9 patients vomit.

In general oseltamivir (Tamiflu) is safe and the influenza vaccine is safe. They are also both somewhat, though not gloriously, effective. Both are lucrative for the companies that make them. The flu is a huge public health issue, causing death and disability and work and school loss, and it repeats itself yearly, with varying intensity. Because control of the flu, even shortening illness by a day or decreasing transmission just a bit, is so very important on a population level it is likely that the down side to an individual will tend to be minimized. As an individual and as a member of a human herd, I will continue to get yearly flu vaccines and nudge my dear ones to do the same. If I wake up feeling like I got hit by a truck and then nanobots have attacked my mucus membranes with sandpaper I will probably take one of the anti-flu drugs (but maybe zanamivir, since it is cheaper and probably won't make me jump off a balcony.) These are decisions, though, that individual patients should make after being fully informed of both effectiveness and potential side effects.

Janice Boughton, MD, ACP Member, practiced in the Seattle area for four years and in rural Idaho for 17 years before deciding to take a few years off to see more places, learn more about medicine and increase her knowledge base and perspective by practicing hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling. Disturbed by various aspects of the practice of medicine that make no sense and concerned about the cost of providing health care to every American, she blogs at Why is American Health Care So Expensive?, where this post originally appeared.