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Clinical Trial Follow-up Evaluates Safety and Effectiveness of Saw Palmetto and Stinging Nettle Extracts in Men with BPH
Reviewed: Lopatkin N, Sivkov A, Schläfke S, Funk P, Medvedev A, Engelmann U. Efficacy and safety of a combination of Sabal and Urtica extract in lower urinary tract symptoms—long-term follow-up of a placebo-controlled, double-blind, multicenter trial. Int Urol Nephrol. 2007;39(4):1137-1146.

Benign prostatic hyperplasia (BPH) is a noncancerous enlargement of the prostate gland, and it is the leading cause of lower urinary tract symptoms common in older men. Lower urinary tract symptoms include obstructive symptoms (decreased urine flow, interrupted flow, feelings of incomplete emptying, and hesitancy) and irritating symptoms (urge to urinate, frequent urination, and nighttime urination). Although there are medications available to reduce BPH symptoms, many men find the adverse effects unacceptable. There is great interest in herbal remedies that are well-tolerated and effective for continuous, long-term use. Extracts from saw palmetto (Serenoa repens, Arecaceae) and stinging nettle (Urtica dioica, Urticaceae) are the most widely used herbal remedies for BPH. This article presents the results of a long-term follow-up of a clinical trial evaluating the safety and effectiveness of a combination of saw palmetto and stinging nettle in men with BPH.

The study was conducted at 3 outpatient urology clinics in Moscow, Russia. The subjects were men over the age of 50 with a diagnosis of BPH. The herbal product studied was PRO 160/120, which provided 160 mg ethanolic extract of saw palmetto fruit (WS® 1473) and 120 mg ethanolic extract of stinging nettle root (WS® 1031) per capsule (Dr. Willmar Schwabe GmbH & Co., Karlsruhe, Germany; marketed as Prostagutt forte(r)). In the double-blind portion of the trial, 257 men were randomly assigned to receive 2 capsules per day of PRO 160/120 or placebo for 24 weeks. In the open-label control portion of the study, 250 subjects took 2 capsules per day of PRO 160/120 for 24 weeks. After the open-label portion of the study, 219 subjects were offered an additional 48 weeks of open-label follow-up in which they continued to take 2 capsules per day of PRO 160/120. The subjects returned for study visits every 12 weeks. The investigators used ultrasound and electronic urinary flow meters to evaluate maximum urinary flow rate, duration, output, residual urine volume, and prostate size. The subjects rated their symptoms using the International Prostate Symptom Score (I-PSS) questionnaire.

In the 24-week double-blind portion of the study, subjects taking PRO 160/120 reported significant improvements in I-PSS scores compared to subjects taking the placebo (P < 0.02). Tolerability of PRO 160/120 was comparable to that of placebo. During the 24-week, open-label control period, subjects who switched from placebo to PRO 160/120 (the Ex-Placebo Group) had substantial improvements in their I-PSS scores and subjects continuing on with PRO 160/120 had additional mild improvements (P values not reported). By week 48, subjects in both groups reported a median improvement of 7 points in I-PSS scores.

A total of 219 subjects continued in the follow-up study. From week 49 to week 96, I-PSS scores improved by a median of 1 point. Subjects reported 61 adverse events during the follow-up study; only one adverse event was assessed as being possibly related to PRO 160/120 treatment.

I-PSS scores improved significantly by 9 points from baseline to week 96, which corresponds to a 53% reduction from the baseline median of 17 points (P < 0.001). Similar improvements were reported for both the obstructive and irritating symptoms, and the improvement in each of the 7 individual symptom scores was statistically significant (19%) (P < 0.01). Maximum urinary flow and average urinary flow values increased significantly (P < 0.01), residual urine volume decreased significantly (44%) (P < 0.03), and prostate volume decreased significantly (P = 0.001) from baseline to week 96.

The authors conclude that PRO 160/120 slows the progression of BPH and provides a clinically relevant benefit over a period of 96 weeks. Long-term administration of this combination of saw palmetto and stinging nettle extracts showed very good tolerability and high acceptance by study participants. Although this study could be criticized for not continuing the randomized control group after the initial 24-week period, the independent ethics committee that approved the study determined that it would be unethical for subjects to go without treatment for longer than 24 weeks. Placebo effects are common in studies investigating medical treatment of lower urinary tract symptoms, but the magnitude of the placebo effect typically decreases over time. The continuous, long-term improvements observed in this study do not appear to be explained by a placebo effect alone.

—Heather S. Oliff, PhD