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

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.

To assess antihypertensive effect, safety and tolerability of EA compared to hydrochlorothiazide (HCTZ).

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.

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.

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.