One Diuretic Remains Supreme

Henry R. Black, MD


May 13, 2013

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Introduction to the Ontario Study on Hypertension in the Elderly

Hi. I'm Dr. Henry Black, Clinical Professor of Internal Medicine at the Langone New York University (NYU) Medical Center, a member of the Center for the Prevention of Cardiovascular Disease at that institution, and former President of the American Society of Hypertension. Today I want to talk about an issue that I didn't think was controversial: whether chlorthalidone and hydrochlorothiazide are equal.

The SHEP study,[1] ALLHAT,[2] and recent guidelines from the NICE group in England[3] have really made the point that chlorthalidone is a superior thiazide-type diuretic to hydrochlorothiazide. I think that's been a universal agreement among hypertension specialists. However, there was a recent paper published in the Annals of Internal Medicine[4] that tends to challenge this. And I want to challenge that paper.

This came from data from Ontario from databases with over a million individuals, all over 65 and all of whom had been hospitalized. This is an important difference because most patients with hypertension aren't hospitalized. So, I don't know how generalizable this is. They looked at different doses -- 12.5 mg of hydrochlorothiazide and chlorthalidone 25 and 50 mg -- and concluded that the starting dose of chlorthalidone was about 40 mg per day, whereas the starting dose of hydrochlorothiazide was 18.7 mg per day.

That isn't how we would use those agents. We would begin with chlorthalidone at 12.5 mg, titrate up to 25, and then not go beyond. And similarly with hydrochlorothiazide, if you're going to use 12.5 mg as a starting dose, 25 is the top dose. That is how we practice in 2013. But it's not necessarily how they practiced with the group that they analyzed. Also, many of the people who got the higher doses of chlorthalidone, sometimes as high as 50 mg, did so for 2 reasons: (1) It was what the Canadian formulary had available at the time, and (2) many of the people who got chlorthalidone usually did so as part of a fixed-dose combination, atenolol 50 mg/chlorthalidone 25 mg. And they may even have gotten 2 tablets. That's very different from how we practice in 2013.


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