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Are All Antihypertensive Agents Safe and Effective? More Evidence, For and Against: First Randomized Clinical Trial Evidence for Blood Pressure Lowering Effect of Hawthorn, UK Researchers Claim

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First Randomized Clinical Trial Evidence for Blood Pressure Lowering Effect of Hawthorn, UK Researchers Claim

The first randomized controlled trial to demonstrate a hypotensive effect of hawthorn in patients with type 2 diabetes taking prescribed medication has been published in the June issue of The British Journal of General Practice.[14] Researchers from the University of Reading in the United Kingdom, led by Ann F. Walker, PhD, say that it is safe to take this natural remedy at the same time as prescribed medication. They used extract of leaves, flowers, and berries from Crataegus laevigata (also known as Crataegus monogyna or oxyacantha), which has previously been investigated as a treatment for hypertension in small-scale human studies, including by Dr. Walker's group.[15]

In the largest trial to date, 80 patients with type 2 diabetes, mean age 60 years, who had SBP levels of 145-165 mm Hg and DBP levels of 85-95 mm Hg, were recruited between 2001 and 2002 from general practices in the Reading area in the south of England. They were mostly male, nonsmokers, and overweight. Patients were randomized to receive a daily dose of either hawthorn extract or placebo for 16 weeks. The 1200-mg dose of hawthorn extract was equivalent to 6 g of dried flowering tops (Faros 600, Lichtwer Pharma, Berlin; extract 3:1, standardized to 2.2% flavonoids).

As many as 71% of the study population were using antihypertensive drugs, including ACE inhibitors, calcium channel blockers, beta-blockers, and diuretics. A number of patients were also taking hypoglycemic drugs, including low-dose insulin, metformin, and gliclazide. The mean number of hypoglycemic and/or hypotensive drugs was 4.4.

The patients taking hawthorn had a significant reduction in mean DBP over 16 weeks compared with those on placebo (-2.6 vs +0.5 mm Hg, P = .035). There was no difference between the 2 groups with regard to mean SBP reduction, although a nonsignificant (P = .096) decline of 3.6 mm Hg was seen in the hawthorn group, Dr. Walker and her colleagues reported. There was no significant outcome difference between groups in the indices of glycemic control (fasting glucose, glycated hemoglobin, and fructosamine). No herb-drug interactions were found and minor health complaints were reduced from baseline in both groups.

"The blood pressure lowering effect in this study was real, and worked in addition to the drugs being taken by patients," said Dr. Walker. "There has been a great deal of confusing publicity about herbal remedies affecting the efficacy of prescribed drugs, but we were able to confirm there were no side effects or adverse reactions," she said. "As hypertension is such a huge problem in Western societies, any safe, natural approach, which can be used with or without modern drugs, is worth exploring. It is possible to have modern and herbal medicines working in harmony."

The finding that hawthorn has a hypotensive effect in patients with type 2 diabetes taking prescribed medication should stimulate further studies, Dr. Walker believes. She suggests that future research could examine the hypotensive effects of hawthorn for other hypertensive patient groups, including nondiabetic, newly diagnosed patients.

Hawthorn has been extensively studied in Germany, where it has been approved for the treatment of heart failure by the German Commission E, the German governmental agency that evaluates the safety and effectiveness of herbal products. Other countries do not have comparable agencies.

Hawthorn extract is not usually mentioned in conventional hypertension guidelines. The UK Blood Pressure Association warns on its Web site that "there is no evidence of any benefit, in particular, no evidence that it will help to lower blood pressure. It should not be used."[16]

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