Patients often do not take the medicines their doctors prescribe, and a new review of existing research suggests that there is no proven way to get them to follow directions for long periods.
"Simple things don't work and nothing works very well," said review lead author Dr. R. Brian Haynes of the McMaster University Faculty of Health Sciences in Hamilton, Ontario.
Still, doctors can achieve limited success by trying a number of approaches such as sending reminders to patients and following up with phone calls.
Medicine, of course, does not work if patients do not take it and studies have shown that "patient adherence" ó taking drugs as prescribed ó is far from guaranteed, even in those with life-threatening conditions.
One 1979 study estimated that patients only take half of the doses of the prescription medications they administer themselves. Few people take all of their medications and many do not bother to take any, Haynes said.
Not surprisingly, a failure to take prescribed medications is associated with higher death rates. "With growing numbers of treatments that work when taken, the gap between the potential benefits of current treatments and the actual benefits continues to grow," Haynes said.
There are many potential reasons why patients might not bother to take their medications; they can include mental illnesses, such as depression, or the complexity of drug regimens for conditions like diabetes, Haynes said.
The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
For the review, which updates a 2005 review, Haynes and colleagues included studies that were randomized, controlled trials, meaning that researchers randomly assigned patients to different groups then compared the results.
The studies had to look at both adherence and outcome ó what happened to the patients medically.
While hundreds of studies have looked at patient adherence, the review authors only found 78 that met their criteria. They included patients with a variety of diseases, such as high-blood pressure, heart failure and HIV.
Some studies looked at short-term adherence to drug regimens ó between one and three weeks.
In nine of these studies, four of 10 strategies seemed to improve proper drug taking and improve patients' health in at least one way. (For example, one strategy helped the patients take their drugs properly, but did not make them get better.)
These findings suggest that simple approaches can be effective, Haynes said. Among others, approaches that are more successful include counseling and providing written instructions and pill packaging that helps patients take their drugs properly ó like the day-by-day dose packaging for birth-control pills.
Getting patients to take their drugs over long periods is much more challenging. Just 25 of 81 strategies ó reported in a total of 69 studies ó actually helped patients get better. Thirty-six strategies led to improved adherence.
The review authors found that almost all of the more successful long-term strategies were complex "combinations of more convenient care, information, reminders, self-monitoring, reinforcement, counseling, family therapy, psychological therapy, crisis intervention, manual telephone follow-up and supportive care."
Even the most effective strategies did not lead to major improvements in adherence or the health of patients.
Debra Roter, a professor at Johns Hopkins Bloomberg School of Public Health, said the review has limitations. The studies examined are indeed rigorous, she said, but "in real life, you don't have such rigorously controlled circumstances."
According to Roter, a commitment to the most rigorous research methods often produces strategies that are simplistic and inflexible. "You need community-based observational studies that have all the messiness of what patients do in everyday life."
What to do? Study lead author Haynes says doctors need to emphasize the importance of taking drugs properly and try to spend more time with patients who fail to do so.
"Teamwork can help: nurses, pharmacists, sometimes a family member or friend," he said.
As for patients, they need to be honest with their doctors about whether they skip doses of medicine, Haynes said. "Your doctor can't tell if you are not taking your meds and may over-prescribe if she thinks it isn't working when, in fact, you aren't taking it."