Does Enzyte make anything longer?

August 31, 2010, 7:06 pm


Effect of Enzyte on QT and QTc Intervals. Phillips M et al. Arch Intern Med Aug 9/23 2010;170:1402-1404


Enzyte — sold over-the-counter as an herbal supplement — is marketed as an agent for “natural male enhancement”.  Its ingredients include:

This study, from the Chicago College of Osteopathic Medicine, had 9 healthy young male subjects ingest either placebo or varying doses of Enzyte, and then measured the QTc interval (determined by Bazett’s Formula) at 1, 3, and 5 hours after ingestion.  The primary ECG end point was the maximum relative increase in the QTc between baseline and any of the three post-ingestion measurements.

The authors found modest seemingly insignificant increases in the QTc after the subjects ingested Enzyte, but these seem to me clinically insignificant.  In fact, the differences between the groups were so small, the research methods so murky (exactly how were the QTc intervals determined?), and the confidence intervals so wide (in some groups roughly 10 – 70%) that I was not able to get any useful information from the data.  None of the measured QTc intervals approached the 500 msec that is generally considered a risk factor for development of torsades de pointes. Unfortunately, the authors do not discuss how or why they became interested in the effects of Enzyte on the QTc, nor the fact that niacin has previously been associated with QTc prolongation (even though niacin is one of the ingredients in Enzyte, and 4 of their 9 subjects experienced the severe cutaneous flushing reaction that is characteristic of niacin).

Enzyte is familiar to many people from the ubiquitous “Smilin’ Bob” ads on late-night cable TV. Here’s one of SB’s greatest hits:


  1. Graham Says:

    That’s a freaking hilarious title. And thanks for the MDCalc link!

  2. Neuroskeptic Says:

    Is “Horny Goat Weed” a real folk name for Epimedium, or is it just a marketing invention by people who want to sell it as a sex pill?

    Wikipedia says that it was used in traditional Chinese medicine to treat impotence, so I guess it does have some history…

  3. Leon Says:


    Glad you enjoyed the title! And thanks for MDCalc — an amazingly useful site.


    I’m no W.C. Minor, but I’ve heard that the term “horny goat weed” goes back to the agrarian past, when a shepherd tending his flock noticed that after grazing on a particular plant, his goats became . . . frisky. Like sildenafil, epimedium seems to increase production of nitric oxide.