Cyvita

Cyvita is a formulation of two common forms of the metabolite carnitine, Glycine propionyl-l-carnitine and Acetyl L-carnitine, that is supposed to "enhance" the performance of Viagra (Sildenafil) in male users.

The claims
Cyvita is described by its makers as containing 2,000 mg of carnitine. Its claims that the product is clinically tested actually refer to carnitine being generically tested, not their own "proprietary blend".

One study, published in the Journal of Urology, reported a statistical increase in heart function and nighttime erections for both testosterone and carnitine users, with carnitine having better results, and according to an erection quality test. The study ran six months, and did not combine these with Viagra.

A second study, by the same researcher and published in the same journal, found an increase in response, in prostate surgery patients, to Viagra when taking carnitine.