GPs braced for BP challenge
NICE leaves GPs with dilemmas over ß-blocker switch and first-line drug choice, Daniel Cressey reports
NICE brought an end to two years of intrigue and controversy last week when it finally came to an agreement with the British Hypertension Society on new joint guidelines for treating high blood pressure.
The guidance pulls back from sidelining diuretics, but is still the first in the world to recommend calcium channel blockers first-line and a radical departure from current practice.
For white patients over 55 and black patients of any age, the guidance recommends calcium channel blockers or diuretics first-line, while younger patients should be treated with ACE inhibitors.
In May, 3.4 million hypertensives were on diuretics and 2.4 million were on calcium channel blockers, figures from private analysts CompuFile reveal. But 2.3 million were on ß-blockers and NICE experts believe 80 per cent of these will eventually move to diuretics or calcium channel blockers.
So how should GPs handle a mass switch of patients, and which drugs should they use?
At the media briefing to launch the guidelines, experts were keen to stress that no one needed to see their GP urgently and ß-blockers were totally safe.
But Professor Bryan Williams, a member of the guideline development group and professor of medicine at the University of Leicester, admitted: 'It's inevitable when people are aware of the evidence they will want to change.'
Predictably enough, newspapers proclaimed 'Two million warned on blood pressure tablets' and surgeries were soon inundated by worried patients.
Dr Ahmet Fuat, a GP in Darlington and CHD lead for Darlington PCT, says: 'I feel angry at the media. I agree ß-blockers shouldn't be first-line but we have patients who stopped their ß-blockers suddenly.'
Dr Rubin Minhas, a GP in Gillingham and CHD lead for Medway PCT, says: 'It's very important ß-blockers are not stopped suddenly – they should be withdrawn slowly over a
period of weeks.'
The NICE guidance makes clear patients with conditions such as heart failure or angina should remain on ß-blockers and the drugs can still be considered for younger patients.
Professor Williams advises: 'Normally we would halve the dose over a week and then halve it again. There's no hard and fast rule in this.'
The costs of switching patients from ß-blockers to calcium channel blockers or diuretics will be substantial. NICE insists the switch to more effective diuretics and calcium channel blockers will save £221 million. But its cost analysis admits £58 million will first have to be spent to realise those gains.
There are significant differences in the costs of drugs – between classes and within the same class. Amlodipine, the most popular calcium channel blocker, costs more than seven times bendroflumethiazide, the most popular diuretic.
Dr Anthony Brzezicki, prescribing lead for Central Croydon PCT, believes trusts will be keen to ensure GPs use cheaper drugs. 'I'm sure PCTs may have a view on what they would recommend, bearing in mind NICE has skirted the cost completely. There is still a considerable cost implication,' he says.
The guidance warns the costliest calcium channel blockers are not likely to be cost-effective for the NHS, but there are particular circumstances when the drugs will be preferred.
Dr Mark Davis, another member of the guideline development group and board member of the Primary Care Cardiovascular Society, says: 'If people are centrally obese or with impaired fasting glucose I would use a calcium channel blocker.'
But GPs will have to balance a reduced rate of diabetes with calcium channel blockers – which make them preferable for south Asians and the obese – with evidence they are less effective at preventing heart failure.
A meta-analysis considered by NICE found that while calcium channel blockers and diuretics had effects on incidence of MI, stroke and death, heart failures were 'significantly higher' with calcium channel blockers.
NICE may have sat on the fence in the choice between drug classes, but GPs are relieved it has ended its long-
running feud with the BHS.
Dr Mike Mead, a GP in Leicester and chair of the Blood Pressure Association's advisory group, says: 'At last we've got concordance between the different bodies.'
Managing ß-blockers switch
•Around 20 per cent of patients with heart failure, angina or previous myocardial infarction can stay on ß-blockers
•The drugs can still be considered for younger patients, particularly women of child-bearing age
•No hurry to switch – but could be done at a patient's next routine appointment
•Patients should be titrated down gradually
Diuretic or channel blocker?
•ALLHAT found that a thiazide-type diuretic was better than a calcium channel blocker or an ACE inhibitor for preventing major forms of cardiovascular disease
•A recent sub-study of ALLHAT also found treatment with a diuretic was the most effective option for preventing heart failure
•ASCOT found a calcium channel blocker and an ACE inhibitor prevented more cardiovascular events and induced less diabetes than a diuretic and ß-blocker
The Lancet 2005;366:895-906
•The INSIGHT study found a calcium channel blocker and a diuretic were equally effective for preventing cardiovascular complications
The Lancet 2000;356:366-72
•Final results of the MIDAS study found a higher incidence of major vascular events with a calcium channel blocker than a diuretic