Would using l-arginine capsules (to provide nitric oxide) in combination with sildenafil and grapefruit juice allow patients with erectile dysfunction to reduce the dose of sildenafil?
—Alberto Saenz, MD, Columbia, S.C.

A double-blind, placebo-controlled study of high-dose l-arginine (5 g/day) done in 50 patients, aged 50-75, over six weeks showed no difference on the Brief Male Sexual Function Inventory—a standard questionnaire for evaluating subjective responses to treatment for sexual dysfunction. Nor was there any change in hemodynamic parameters. However, about one third of participants demonstrated improvement on their sexual diary scores. This subset of patients was found to have lower baseline urinary nitrate levels, indicating that L-arginine may be of some value in those with low levels of nitric oxide (Campbell’s Urology. 8th ed. Walsh PC, Retik AB, eds. Philadelphia, Pa.: WB Saunders; 2002:1655). Grapefruit juice has been reported to both increase and also delay the absorption of sildenafil, making the effectiveness of this combination somewhat unpredictable. Therefore, taking sildenafil with grapefruit juice is generally not recommended. I’m not sure I understand the benefit of “reducing” the sildenafil dosage.
—David T. Noyes, MD (102-6)

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