Antihypertensive effect of Equisetum arvense L.: a double-blind, randomized efficacy and safety clinical trial.

BACKGROUND: Equisetum arvense L. (EA) is a traditional phytomedicine used as a diuretic agent worldwide and regulated strictly by European Medicine Agency (EMA) and Brazilian National Health Surveillance Agency (ANVISA). However, few studies evaluating its efficacy and safety have been published and no clinical trial assessing its antihypertensive effect has been reported to date. PURPOSE: To assess antihypertensive effect, safety and tolerability of EA compared to hydrochlorothiazide (HCTZ). METHODS: This is a double-blind randomized clinical trial, allocating 58 systemic arterial hypertension (SAH) stage I patients (both sexes, 25-65 years old) into two groups (EA and HCTZ). All patients underwent biochemical and cardiologic checkup prior to and during interventions. The EA standardized dry extract (900 mg/day) or HCTZ (25 mg/day) were administered for 3 months and follow-up visits were conducted every 30 days. Efficacy established goals were systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) decreases ≥ 10.0 mmHg and/or casual blood pressure (CBP) < 140/90 mmHg. RESULTS: EA treatment demonstrated a significant antihypertensive effect, promoting a mean decrease of SBP and DBP by 12.6 and 8.1 mmHg, respectively, and resulting a CBP mean of 134.0/84.5 mmHg at the end of intervention on the SAH stage I patients (CBP mean of 148.5/95.7 mmHg). There were no significant statistical differences between EA and HCTZ interventions on blood pressure decrease, and before-after treatments regarding to biochemical tests and signs of acute toxicity, renal, hepatic and hematologic alterations. A slight trend but no significant difference were observed between adverse events from EA (3.58%) and HCTZ (4.68%) groups. CONCLUSION: EA standardized dry extract was successfully applied to the SAH stage I patient treatment, decreasing effectively SBP ad DBP values to the reference normal ranges, and demonstrating a well-tolerability profile similar to HCTZ intervention.

Randomized, Double-Blind Clinical Trial to Assess the Acute Diuretic Effect of Equisetum arvense (Field Horsetail) in Healthy Volunteers.

In this double-blind, randomized clinical trial, 36 healthy male volunteers were randomly distributed into three groups (n = 12) that underwent a three-step treatment. For four consecutive days, we alternately administered a standardized dried extract of Equisetum arvense (EADE, 900 mg/day), placebo (corn starch, 900 mg/day), or hydrochlorothiazide (25 mg/day), separated by a 10-day washout period. Each volunteer served as his own control, and the groups' results were compared. We repeated the same evaluation after each stage of treatment to evaluate the safety of the drug. The diuretic effect of EADE was assessed by monitoring the volunteers' water balance over a 24 h period. The E. arvense extract produced a diuretic effect that was stronger than that of the negative control and was equivalent to that of hydrochlorothiazide without causing significant changes in the elimination of electrolytes. There was no significant increase in the urinary elimination of catabolites. Rare minor adverse events were reported. The clinical examinations and laboratory tests showed no changes before or after the experiment, suggesting that the drug is safe for acute use. Further research is needed to better clarify the mechanism of diuretic action and the other possible pharmacological actions of this phytomedicine.