One study examined the effect of administering testosterone undecanoate versus propionyl-L-carnitine plus acetyl-L-carnitine and placebo in the treatment of male ageing symptoms for a period of 6 months . The researchers enrolled 120 patients (mean age 66 years) and randomized them into three groups. Group 1 received testosterone undecanoate 160mg/d, group 2 received propionyl-L-carnitine 2 g/d plus acetyl-L-carnitine 2 g/d, and the third group were given a placebo (starch).
The testosterone and carnitine groups (1 and 2) showed significantly improved peak systolic velocity, end-diastolic velocity, resistive index, nocturnal penile tumescence and International Index of Erectile Function (IIEF) score. This effect was noted for as long as the drugs were administered, with a suspension resulting in a reversal to baseline parameters. Placebo was ineffective in improving any of the above parameters. The researchers concluded that testosterone and, especially, car-nitines proved to be active drugs for the therapy of symptoms associated with male ageing .
Another double-blind, fixed-dose study examined the efficacy and tolerability of oral propionyl-L-carnitine (PLC) plus sildenafil in men with ED and diabetes unresponsive to sildenafil monotherapy .
Patients with documented ED of organic or mixed aetiology and diabetes unresponsive to at least eight doses of Viagra alone were randomized to receive oral PLC (2 g/d) plus sildenafil (50 mg twice weekly) (20 patients, group 1) or sildenafil alone (20 patients, group 2).
After 24 weeks, group 1 (PLC and Viagra) showed a significantly greater percentage of improved erections (68% vs. 23%) and successful intercourse attempts (76% vs. 34%) compared to Viagra alone . No patient discontinued treatment, suggesting that PLC is well tolerated.
Cavallini and colleagues investigated the use of two forms of carnitine - PLC and acetyl-L-carnitine (ALC) - in 96 patients who had undergone bilateral nervesparing radical retropubic prostatectomy . One group were given a placebo (33 men), another group were given PLC 2 g/d plus ALC 2 g/d plus 100 mg of sildenafil when needed (32 patients), and the third group received sildenafil alone (35 men).
Placebo was found to be ineffective. The IIEF score of patients receiving PLC plus ALC and sildenafil were significantly greater than that of patients receiving sildenafil alone. The authors concluded that PLC and ALC were safe and reliable in improving the efficacy of sildenafil after surgery without increasing the side effect profile .
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