People with diabetes often have a number of coexisting health problems. So in addition to insulin or diabetes pills, other drugs are often needed to control these problems — statins for high cholesterol, diuretics or beta-blockers for high blood pressure, antidepressants for depression or neuropathy pain, and a daily aspirin to prevent a heart attack. But some drugs are not supposed to be taken simultaneously, and doctors and pharmacists don’t always notice when a person is taking dangerous or risky drug combinations.
What can happen to you if you take several drugs that are not supposed to be taken together? This article explains why and how medicines can interact and what a drug interaction may mean for you and your health care.
The scope of the problem
Surprisingly, most drug reactions are caused by a small group of commonly prescribed drugs. The nonsteroidal anti-inflammatory drugs (such as ibuprofen), anticoagulants, diuretics, and drugs to treat diabetes are on this list. Adverse drug reactions may add as much as $130 billion a year to the cost of health care in the United States. A significant portion of adverse drug reactions are caused by interacting drugs. This is a huge problem and much research and effort is going into trying to reduce the incidence and risk of these interactions.
It is estimated that people over 65 take an average of seven drugs at any one time to treat a variety of illnesses. With this amount of medicine use, the probability that a person will take two prescribed drugs that may interact with one another is very high. In a recent study done in six European countries, investigators reviewed the medicines taken by about 1600 people and found that 46% were taking at least one pair of drugs that could interact. (Studies that include people under age 65 have shown somewhat lower percentages of people taking interacting drugs.) Although not all potential drug interactions result in a bad outcome, drug interactions contribute to an increased risk of an adverse event. In fact, up to 7% of people who are admitted to hospitals end up there because of an adverse drug reaction.
One might think the risk of drug interactions would be lower in the hospital, where patients are under close medical supervision, but the opposite is true: The problem is even greater for people admitted to a hospital. On average, a person who enters the hospital is treated with 10 drugs and has about a 20% probability of having a reaction caused by drug interactions.
With all of the drugs on the market today, how many drug interactions are possible? The answer is quite a few. Fortunately, while there are a lot of potential drug interactions, not all of them result in adverse drug reactions. Why this is so is not well understood but may include underreported or unrecognized adverse drug events by the people taking them or their physicians, people simply not taking their medicines consistently, individual differences in tolerance of drug effects, and individual variations in the blood levels of any of the potential interacting drugs.
Why and how drugs interact
When you take a drug, most of it must be absorbed into your bloodstream and go to the particular part of the body it needs to affect. After it has produced its effect, the body needs to get it out of the system. Interference with any of these steps, whether drug-induced or from physiological problems, can produce unwanted effects. The most common form of drug interaction occurs when one drug interferes with another drug’s elimination from the body.