Dear Doctor: Do you, or do you not, need to take a whole course of antibiotics even when you begin to feel better? I’ve always dutifully done so, but new reports seem to suggest otherwise.
Dear Reader: Antibiotics have undoubtedly saved countless lives. My grandfather died from pneumonia in the 1940s, before antibiotic use became common, and I often wonder about his likelihood of survival in the 1950s, when the drugs were more readily available. Today, we’ve almost come full circle. We now live in a world in which some bacteria no longer succumb to the common drugs used against them, and we fear that the overuse of antibiotics may lead to further resistance. At the same time, more powerful antibiotics are used only when an infection is resistant to all other antibiotics, and drug companies lack incentives to develop new antibiotics.
That brings us to the essential question: How best to prevent drug resistance among patients given antibiotics? In July, a group of infectious disease specialists and microbiologists in England published an editorial in the British Medical Journal arguing that lengthy courses of antibiotics could actually increase resistance. Continuing to give antibiotics after they’ve done their job doesn’t make sense, they said, and isn’t backed up by science. They have a point. Although a few studies have assessed the appropriate duration of antibiotic use for specific conditions, overall, research is slim.
The “take all your antibiotics” advice stems from a long-held worry that bacteria not killed by the antibiotic could develop resistance to that antibiotic. The problem is, bacteria are not one-size-fits-all. Some bacteria, such as those that cause tuberculosis, gonorrhea, salmonella and malaria, can quickly become resistant to antibiotics, so it is important to kill them completely. Other bacteria are slower to develop resistance, so to have some lingering bacteria is less problematic. What is more worrisome about long regimens of antibiotics is that they also affect other bacteria that reside normally in our bodies, not causing infections. Not only do the “good” bacteria suffer, some of the “bad” bacteria can become resistant to that antibiotic and later cause infections that cannot be killed by the prior drug.
As I mentioned, some studies have indeed assessed the duration of antibiotic regimens — and the results have been mixed. For kidney infections, a seven- to 10-day course of antibiotics has shown equal efficacy as a 14-day course. However, in other circumstances, such as ear infections in children, there is greater benefit in taking antibiotics for 10 days than five days. This also is the case for strep throat.
Complicating matters is the nature of various antibiotics themselves. The antibiotic azithromycin, for example, has a half-life of three days, meaning that although a typical course is only five days, the drug stays in your system for many days after you finish.