July 17, 2014
News Review From Harvard Medical School -- Potassium May Cut Death Rates with Diuretics
Giving extra potassium to everyone taking "water pills" might help people with heart failure live longer, a study suggests. Loop diuretics are often given for heart failure, which can cause people to retain fluid. Loop diuretics remove fluid through urine. But this also removes the important mineral potassium. The new study looked at Medicaid and death records for people in 5 states. Researchers focused on 360,000 Medicaid patients who began taking loop diuretics (often called "water pills") in a 6-year period. About half of them were prescribed potassium pills at the same time they got their first diuretic prescription. They were compared with similar patients who did not get potassium pills. About 9% of those in the study died each year. But death rates were lower for those who received a prescription for potassium at the same time as the loop diuretic. For those who took at least 40 milligrams a day of the diuretic, death rates were 16% lower if they also took the potassium supplement. Death rates were 7% lower with potassium for those who took a smaller diuretic dose. The journal PLoS One published the study online. HealthDay News wrote about it July 16.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Doctors most often prescribe a type of water pill called a loop diuretic for people who retain a lot of water. Usually the reason is heart failure. Examples of loop diuretics are furosemide (Lasix) and torsemide (Demadex).
Loop diuretics cause the kidneys to make more urine. But they also cause the kidneys to lose potassium along with the extra urine. Some people lose (excrete) very little potassium in response to loop diuretics. Other people lose a lot of potassium.
This study suggests that for both groups it may be a good idea to take a little extra potassium with a new loop diuretic, starting on day one.
Today, when doctors first start a loop diuretic, they usually have the person get a blood check for potassium a few days later. If the potassium is low, the doctor will prescribe a potassium supplement.
Fewer doctors routinely prescribe potassium pills when they start patients on loop diuretics.
Both strategies are accepted as good practice. However, this new study suggests that starting potassium at the same time as the loop diuretic is linked with longer life than waiting until the potassium is low.
This type of research is called an observational study. It only shows that people who started potassium at the same time as a loop diuretic tended to live longer than those who started the diuretic alone. It does not prove that starting potassium right away actually saved lives.
What Changes Can I Make Now?
Most Americans don't get nearly enough potassium in their diets. We average 2,500 milligrams a day. That's only about half of the 4,700 milligram minimum recommended for adults.
So it makes sense that if you take a loop diuretic you would likely need more potassium. What's surprising is the small amount of extra potassium per day that made a difference in this study. It was 400 milligrams of potassium or less. People prescribed a greater amount of potassium did not have a survival benefit.
If you are starting or already taking a loop diuretic, don't just start taking extra potassium. Get advice from your doctor about taking potassium pills or eating more potassium-rich foods.
There are reasons to be cautious about taking extra potassium. It can be dangerous if your kidneys don't function normally or if you take certain medicines. The drugs often used to treat heart failure cause the body to retain potassium. They include:
- The potassium-sparing diuretics spironolactone (Aldactone) and eplerenone (Inspra)
- Angiotensin-converting enzyme (ACE) inhibitors, such as lisinopril and many others
- Angiotensin receptor blockers, such as losartan, valsartan and many others
What Can I Expect Looking to the Future?
The results of this study won't change current practice right away for most doctors. But more studies will be done to confirm the findings. It would be terrific if taking a small amount of extra potassium when starting a loop diuretic does indeed improve outcomes.