HMI World | Around Harvard

MARCH / APRIL 2007

This article originally appeared in the February 2007 Harvard Health Letter and is provided courtesy of Harvard Health Publications.

Blood pressure drugs can boost blood sugar
Depending on the drug, though, it may not matter.

People with high blood pressure can turn to several types of medication when diet and exercise aren’t enough to rein in their hypertension (see “So many choices”). Each of them does the job. Yet each has its own quirks and costs.

Common side effects range from frequent urination with diuretics to fatigue with beta blockers or a chronic dry cough with ACE inhibitors. While most of the side effects are aggravating or irritating, one that could pose long-term health problems is an increase in blood sugar.

So many choices
Dozens of drugs are available for lowering blood pressure. They work in different ways. Here are the main classes of antihypertension medications and some of their commonly prescribed brands.

Diuretics lower blood pressure by causing the body to rid itself of excess fluids and sodium through urination.

chlorothiazide (Diuril)
chlorthalidone (Hygroton)
furosemide (Lasix)
hydrochlorothiazide (Esidrix, HydroDIURIL)
spironolactone (Aldactone)

Beta blockers decrease the heart rate and output of blood from the heart.

atenolol (Tenormin)
bisoprolol (Zebeta)
metoprolol (Lopressor, Toprol XL)
nadolol (Corgard)
propranolol (Inderal)

ACE inhibitors expand blood vessels and decrease resistance to blood flow.

captopril (Capoten)
enalapril (Vasotec)
lisinopril (Prinivil, Zestril)
ramipril (Altace)
trandolapril (Mavik)

Calcium-channel blockers interrupt the movement of calcium into the cells of the heart and blood vessels.

amlodipine (Norvasc, Lotrel)
diltiazem (Cardizem, Tiazac)
nifedipine (Adalat, Procardia)
nisoldipine (Sular)
verapamil (Calan, Isoptin, Verelan)

Angiotensin receptor blockers do what ACE inhibitors do, but via a different mechanism.

candesartan (Atacand)
eprosartan (Teveten)
irbesartan (Avapro)
losartan (Cozaar)

The sugar connection
Back in 2002, a blockbuster clinical trial known as ALLHAT showed that an old, inexpensive diuretic (chlorthalidone) was at least as good at lowering blood pressure and reducing the risk for heart attack and heart-related death as two newer, more expensive drugs — a calcium-channel blocker (amlodipine) and an ACE inhibitor (lisinopril). The diuretic was better at preventing heart failure. The ALLHAT results led to recommendations that a thiazide diuretic be the first drug a person tries for controlling blood pressure, or at least be part of any combination therapy.

A new look at the ALLHAT data shows that blood sugar levels rose over the course of the trial in people taking any of the three drugs. After six years, the increase was largest among those taking the diuretic (almost 13 milligrams of blood sugar per liter of blood or mg/L) and lowest among those taking the ACE inhibitor (9.3 mg/L). Diabetes developed in 14% of people taking the diuretic, 11% of those taking the calcium-channel blocker, and 9.5% of those taking the ACE inhibitor.

Diabetes is a powerful promoter of heart disease. High levels of blood sugar and insulin, the two hallmarks of diabetes, cause damaging changes throughout the circulatory system that can lead to high blood pressure, heart attack, stroke, heart failure, and other cardiovascular conditions. Yet over the course of the ALLHAT study, people taking the diuretic chlorthalidone who developed diabetes weren’t any more likely to have had one or more of these cardiovascular problems than people who didn’t develop diabetes. In contrast, those taking the ACE inhibitor or calcium-channel blocker who developed diabetes were at increased risk of having a heart attack or dying from a heart-related cause.

Are diuretics special?
The ALLHAT results aren’t the first to signal that diuretic-induced diabetes may be less harmful than regular diabetes, or may even be harmless. A 14-year follow-up of the volunteers in a clinical trial comparing chlorthalidone against a placebo in older individuals showed no increase in heart disease, stroke, or premature death in chlorthalidone-taking volunteers who developed diabetes compared to those who didn’t develop diabetes.

These two studies, of course, don’t settle the issue about blood pressure drugs and diabetes. They do make the case for having your blood sugar tested every year or so if you are taking any medication to lower your blood pressure. If you see your blood sugar level creeping upward, the type and intensity of treatment you and your doctor choose could be determined by the blood pressure medication you are taking.

This work also strengthens the case for taking a diuretic. Although this type of drug is not appropriate for everyone, it is a good first option for many people. And if you need two or three medications to lower your blood pressure, a diuretic should probably be one of them.

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