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Horny goat weed (Epimedium / icariin)

TCM 'yin yang huo' for sexual function, icariin has PDE5-inhibitor activity in vitro; clinical RCTs are small.

Why

Horny goat weed (Epimedium spp., yin yang huo) is a TCM herb for kidney-yang deficiency, traditionally used for male sexual function and bone-strengthening. The active icariin is a phosphodiesterase-5 inhibitor in vitro, same mechanism class as sildenafil, but much weaker potency. Small modern RCTs report modest effects; large outcome trials are absent.

How it works

Icariin is a weak PDE5 inhibitor (similar mechanism class to sildenafil but much weaker affinity). Modulates osteoblast activity in vitro, basis of the traditional bone indication. Mild oestrogenic activity at higher doses.

Expected onset · Acute effects within hours (PDE5 inhibition); chronic effects assessed over weeks

How to take

Dosage

Standardised extract: 500 mg twice daily (5–20% icariin).

Timing

Divided 2 times daily

On the label

Standardised to icariin content. Quality-tested for sildenafil/tadalafil adulteration (a recurring issue in this category).

Ideal for

Adults exploring TCM-rooted options for male sexual function or postmenopausal bone density, with awareness that evidence is preliminary and that PDE5 inhibitor pharmacology may be present.

Safety

PDE5-inhibitor activity is real (if weaker than pharmaceutical sildenafil), additive effect with sildenafil, tadalafil and similar; caution with nitrates (theoretical hypotensive crisis risk). Mild antiplatelet effect. Caution with anticoagulants. Adulteration with sildenafil or tadalafil is a documented problem in budget products. Pregnancy and breastfeeding: avoid.

Evidence

At a glance

Shindel 2010 documented PDE5-inhibitor activity for icariin in vitro and animal models. Clinical RCT replication remains small. Preliminary, RCTs exist in non-tier-1 journals but are small or short-duration. No Cochrane review, EMA monograph or EFSA-authorised claim covers the indication.

Limitations

Preliminary, RCTs exist in non-tier-1 journals but are small or short-duration. No Cochrane review, EMA monograph or EFSA-authorised claim covers the indication.

Where to get it

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