Stinging nettle: Alternative treatment for BPH, osteoarthritis, other pro-inflammatory ailments

With a name like stinging nettle, consumers are not likely to sample this perennial plant. Urtica dioica, a herbaceous flowering plant, is considered the porcupine of the plant world. Its leaves and stems have tiny, needlelike fibers that act like hypodermic needles, injecting histamine and other chemicals into the skin. The needles pump a mixture of acetylcholine, histamine, serotonin, moroidin, leukotrienes and formic acid into the epidermis, producing a stinging or burning sensation.¹

Background

Stinging nettle spreads rapidly by means of an aggressive network of underground rhizomes.² The plant has long, serrated, soft green leaves and bears green/brown flowers.² A dense coating of hairy spines on the exterior leaves give the plant its name. The stinging nettle has a long history of medicinal uses. As early as the 10th century, the stinging nettle was used to treat arthritis and other inflammatory conditions.³

Science

One of the more studied uses of stinging nettle extract is in the treatment of benign prostatic hyperplasia (BPH). BPH affects more than 90% of men by age 70 years and treatment costs exceed $11 billion annually in the United States.⁴ Prescription medication for BPH first became available with the introduction of finasteride (Proscar) in 1992.⁵ The drug’s mechanism of action is based on its ability to inhibit 5 alpha-reductase. This enzyme reduces dihydrotestosterone concentrations, which, in turn, reduces the size of the prostate gland and improves urinary flow rates.

In a head-to-head trial, nearly 500 men with BPH were randomized to treatment with a nettle root extract or finasteride. At the end of a six-month trial, there was no statistically significant difference between the two groups, indicating that stinging nettle was at least as effective as finasteride.⁶

In a randomized, double-blind, placebo-controlled trial, 246 BPH patients were given 459 mg dry extract of stinging nettle roots or placebo. The men were followed for one year and monitored for both safety and efficacy. Efficacy was determined by patient’s self-rated scores at baseline and at the end of the trial on the International Prostate Symptom Score (IPSS) instrument. At the end of one year, IPSS scores for the stinging-nettle patients had dropped an average of six points, whereas the scores in the placebo arm dropped slightly more than four points.⁷

In another trial, researchers enrolled more than 600 men with BPH and randomized them to placebo or to nettle extract. Both groups were monitored for 18 months. At the end of six months, 81% of the nettle patients reported subjective improvement in symptoms, compared with only 16% of patients in the placebo group.⁸ In addition, at the end of the trial, post-void residuals dropped more than 50% in the treatment group, compared with no change in the placebo group.⁸

Stinging nettle also is used for the treatment of osteoarthritis. The mechanism of action for oral use is thought to involve the ability of nettle leaf extracts to reduce or block the formation of tumor necrosis factor-alpha and other inflammatory cytokines.³ When used topically as the actual plant, the needle-like structures produce a stinging sensation that is a counter-irritant and also decreases the activity of substance P, a neuropeptide that enhances the transmission of pain impulses.³

Few randomized, placebo-controlled clinical trials have been conducted using nettle extracts for osteoarthritis, but bench research has verified their chemical activity as anti-inflammatory products. Researchers in an open-label trial recruited 23 patients with radiographically diagnosed osteoarthritis and administered a topical cream of nettle extract twice daily for two weeks. Using the standardized Western Ontario and MacMaster Universities Osteoarthritis Index, participants’ scores were compared from baseline to post study. A mean reduction of 4.17 points (24%) was noted, indicating improved function and reduction of pain.⁹

Safety, interactions

Stinging nettle has the potential for significant allergic reactions when used topically or taken orally. It has few interactions when used topically, but oral use can cause gastric disturbance.³ If taken in large quantities, stinging nettle has been shown to reduce BP, lower blood glucose levels and induce urinary tract contractility.³ As such, it can potentially interact with such drugs as antihypertensive and antidiabetic agents.³

How supplied, dosage

For oral use in treatment of BPH, equivalents of 300 mg extract taken once or twice daily for up to a year have been used in studies.³ Topical use for the treatment of osteoarthritis can take the form of a crushed fresh leaf applied to the area for 30 seconds b.i.d. for one week or a compounded cream containing nettle extract, also applied b.i.d.³

Summary

Stinging nettle’s mechanism of action is similar to that of other accepted botanical preparations, such as capsaicin. Thus, stinging nettle is a viable alternative for use in mild-to-moderate BPH, osteoarthritis, and other pro-inflammatory ailments.

Sherril Sego, FNP-C, DNP, is a staff clinician at the VA Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.

From the September 01, 2012 Issue of Clinical Advisor