When you have high blood pressure, you trust your doctor is prescribing the right medication for you. In the UK, doctors follow hypertension prescribing guidelines from the National Institute for Health and Care Excellence (NICE). However, a recent Cochrane Review of first-line drugs for hypertension found the best high blood pressure medication is, in fact, a low dose thiazide diuretic, which is more likely to reduce your risk of stroke, heart attack and overall mortality than any other class of drug. Unfortunately, thiazides are the least used first line antihypertensive.
Contents Of This Article
Blood pressure medications
Six main types of drug are used to treat high blood pressure:
- thiazide-like diuretics
- alpha blockers
- calcium-channel blockers (calcium antagonists)
- angiotensin-converting enzyme (ACE) inhibitors
- angiotensin-II receptor blockers (ARBs).
When your doctor determines that you need an antihypertensive medicine to control your blood pressure, they will select a so-called first-line drug according to the clinical guidelines that underpin best practice.
In the UK, NICE guidelines recommend that you’re offered treatment with an angiotensin-converting enzyme (ACE) inhibitor if you are under the age of 55 years. If you don’t get on well with the ACE inhibitor, which can cause an annoying cough, then you are switched to an angiotensin-II receptor blocker instead.
If you are over the age of 55, or if you are black and of African or Caribbean origin, then you are offered a calcium-channel blocker as a first-line treatment as these were shown to work better in these groups of people. If a calcium channel blocker is not suitable, or causes side effects, then the guidelines suggest offering a low-dose thiazide-like diuretic, such as chlortalidone or indapamide, instead.
So, of all the first-line drugs used as single antihypertensive medicines, the ACE inhibitors, angiotensin-II receptor blockers and the calcium channel blockers are prescribed most frequently. Low-dose thiazides are only used infrequently on their own but the new analysis from the Cochrane Collaboration, published in April 2018, suggests this may not be the right approach.
The best blood pressure medications
The Cochrane systematic review looked at all the evidence from clinical trials involving different first-line drugs for hypertension. Their aim was to see which blood pressure medicines were associated with the lowest risk of heart attack, stroke or overall mortality when used alone.
They searched for studies published between 1946 and 2017, which lasted for at least one year, and which compared either a low-dose thiazide, a high-dose thiazide, a beta-blocker, a calcium channel blocker, an ACE inhibitor, an angiotensin II receptor blocker or an alpha-blocker against controls (which were either a placebo or no treatment).
The review identified 24 trials involving 58,040 people with high blood pressure. Perhaps surprisingly, they found no randomised controlled trials for first line treatment with an angiotensin-II receptor blocker or an alpha blocker.
The results showed high-quality evidence that, compared with controls, people who received first-line treatment with low-dose thiazides were:
- 11% less likely to die from any cause during the course of the studies
- 30% less likely to develop cardiovascular disease
- 32% less likely to experience a stroke
- 28% less likely to develop coronary heart disease.
There was low to moderate quality evidence that, compared with controls, first-line high-dose thiazides reduced the risk of stroke by 53% and total cardiovascular disease by 28% but these higher doses had no significant effect on total mortality.
When it came to first-line treatment with ACE inhibitors, there was low to moderate quality evidence that they reduced mortality by 17%, stroke by 35%, coronary heart disease by 19% and total cardiovascular disease by 24% compared with controls.
And, in the case of first-line treatment with calcium channel blockers, there was only low-quality evidence to support their use, which suggested they may reduce the risk of stroke by 42%, and total cardiovascular disease by 29%, but not coronary heart disease or total mortality.
The overall conclusion was that first-line, low-dose thiazides were most protective for adults with moderate to severe primary hypertension. In fact, no class of drug class improved health outcomes better than low-dose thiazides.
Although first-line ACE inhibitors and calcium channel blockers may have similar effectiveness, the current evidence was of lower quality. Beta-blockers and high-dose thiazides were definitely inferior.
Given that low dose thiazides are not often used to treat hypertension (and are considered rather old-fashioned), this result may prompt a review and change of existing treatment guidelines – especially as thiazides are cheap as chips compared to other first line high blood pressure medicines.
Step 2 treatment for high blood pressure
Only around one in ten people with hypertension just need one drug to control their blood pressure, of course. Two out of three people with high blood pressure need two classes of drug to reach their target blood pressure, while around one in four people with high blood pressure need three or more classes of antihypertensive drug to achieve good control (assuming you remember to take them).
When you need a two classes of drugs, current guidelines suggest that your doctor prescribes a combination treatment with a calcium channel blocker plus either an ACE inhibitor or an angiotensin-II receptor blocker. If a calcium channel blocker is not suitable for any reason, then a low-dose thiazide diuretic comes into play.
Step 3 treatment for hypertension
If taking two different classes of drug don’t control your blood pressure, then you will be offered a combination of three drugs:
- an ACE inhibitor or angiotensin II receptor blocker
- a calcium-channel blocker
- plus a low-dose thiazide diuretic.
If these three blood pressure medications don’t control your blood pressure, then a fourth antihypertensive drug may be added in or your low dose thiazide may be increased to a higher dose thiazide diuretic.
If you are concerned about any aspect of your high blood pressure medicine, do talk to your doctor or pharmacist.
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