King Dong capsules each contain 400 mg of L-citrulline and 150 mg of trans-resveratrol, with a recommended dosage of two capsules per day (totaling 800 mg of citrulline and 300 mg of resveratrol daily).
The formulation is based on two key human studies that demonstrate the benefits of these ingredients, especially when combined with prescription ED medications.
The first study
In the 2018 trial published in Sexual Medicine Open Access, men with erectile dysfunction who were already taking phosphodiesterase-5 inhibitors but still had suboptimal results were given 800 mg of citrulline plus 300 mg of resveratrol each day for one month, compared to placebo during a separate month.
When taking the supplement, these men experienced a 32 percent improvement in their overall erectile function score (SHIM-T) versus placebo. Their erection confidence (SHIM-1) rose by 45 percent, firmness improved by 35 percent (SHIM-2), intercourse satisfaction increased by 40 percent (SHIM-5), and erection hardness (EHS) improved by 17 percent.
In practical terms, participants reported firmer and longer-lasting erections, significantly greater confidence in maintaining those erections, and a noticeably higher level of satisfaction during intercourse.
The second study
A follow-up study in the World Journal of Men’s Health in 2021 used a similar daily dose of citrulline (800 mg) and resveratrol (300 mg) as part of a multi-ingredient drink taken for two weeks, alongside continued PDE5i therapy.
Although this trial also included other ingredients, the improvements observed in erection firmness (SHIM-2) and erection hardness (EHS) mirrored the earlier findings. Participants again reported firmer, more reliable erections, and their scores for sexual desire and confidence (SHIM-1) showed a marked increase. Intercourse satisfaction (SHIM-5) improved by roughly 35–40 percent compared to placebo.
These results reinforce the conclusion that adding citrulline and resveratrol can significantly enhance the effectiveness of prescription ED medications.
Why add Piperine?
Resveratrol is known to possess antioxidant, endothelial-supporting, and vasodilatory properties but suffers from poor bioavailability when taken alone because much of it is metabolized before entering the bloodstream.
To address this, King Dong includes piperine, an extract from black pepper that has been shown to increase resveratrol absorption by more than 200 percent.
In a study by Bhaskaran and colleagues (2012), co-administration of piperine (20 mg) with resveratrol (25 mg) raised resveratrol’s total blood exposure by approximately 229 percent and peak concentration by about 154 percent, compared to resveratrol given alone.
By including piperine alongside trans-resveratrol, King Dong ensures that its 150 mg of resveratrol per capsule is absorbed efficiently, allowing more of the active compound to reach circulation and exert its effect on nitric oxide pathways within erectile tissue.
Why Citrulline and not Arginine?
Both citrulline and arginine can serve as precursors to nitric oxide (NO), which dilates blood vessels and improves blood flow. King Dong uses L-citrulline rather than arginine because citrulline bypasses first-pass metabolism in the gut and liver; it is converted into arginine in the kidneys, producing a more sustained rise in blood arginine levels.
So, rather ironically - supplementing with citrulline leads to greater arginine blood levels, than supplementing with arginine itself.
A clinical comparison by Kharitonova and colleagues (2020) found that oral citrulline produced a significantly larger and longer-lasting increase in blood arginine than the same dose of arginine itself. In practical terms, citrulline delivers a steadier and more reliable boost in nitric oxide production, which is essential for maintaining erection firmness and duration.
Choosing citrulline ensures King Dong provides consistent support for NO production and better overall erectile function.
In summary
When taken twice daily, King Dong delivers the clinically studied doses shown to enhance erection hardness and duration.
In the clinical trials, men who used these doses alongside their ED medication experienced firmer, longer-lasting erections with an approximately 35 percent increase in erection firmness and a 17 percent increase in erection hardness compared to placebo.
Participants also reported a 45 percent increase in erection confidence and a 40 percent increase in intercourse satisfaction.
By adding piperine to improve resveratrol’s bioavailability and choosing citrulline over arginine for a more sustained nitric oxide response, King Dong offers a science-backed formula that helps users achieve and maintain firmer erections more consistently.
If you are looking for a natural, clinically validated way to enhance erectile function—whether you have mild, moderate, or medication-resistant ED (or even if you don't suffer ED and just want to enhance your performance)—King Dong’s combination of 800 mg L-citrulline and 300 mg trans-resveratrol (taken as two capsules per day) provides a proven approach to improving firmness, confidence, and intimacy.
References:
Shirai T. et al. (2018). Adjunctive L-Citrulline + Trans-Resveratrol in PDE5i-Treated ED Patients. Sexual Medicine Open Access, 6(4): 291–296.
Shirai T. et al. (2021). Multi-Ingredient Supplement (L-Citrulline + Trans-Resveratrol + Others) in PDE5i Users. World Journal of Men’s Health, 39(4): 733–739.
Bhaskaran N. et al. (2012). Piperine Enhances Resveratrol Bioavailability. European Journal of Pharmaceutical Sciences, PMC3295233.
Kharitonova M. et al. (2020). Citrulline vs. Arginine Supplementation in Healthy Volunteers. PMC7274894.
Here's a video summary around the primary study: