Phentolamine

Also known as: phentolamine, phentolamine mesylate, Vasomax (branded, oral), Regitine (branded)

Sexual Well-Being

In plain English

Phentolamine relaxes blood vessels and is used to help erections, either as part of an injectable 'Tri-Mix' or in oral combinations. It works by blocking a signal that keeps blood vessels constricted. An oral version was studied for erectile dysfunction but is not FDA-approved for that use in the U.S. Injectable phentolamine is a component of penile-injection therapy.

The science

Phentolamine is a competitive, non-selective alpha-1/alpha-2 adrenergic antagonist that reduces sympathetic vasoconstrictive tone in penile smooth muscle, facilitating cavernosal blood inflow. As a component of intracavernosal Tri-Mix (with papaverine and alprostadil) it contributes to reliable erections, including in men who fail oral therapy. Orally, phentolamine mesylate (Vasomax) improved erectile-function scores versus placebo in phase 3 trials but was less effective than sildenafil in comparative studies and is not FDA-approved for erectile dysfunction in the U.S. Adverse effects include nasal congestion, dizziness, reflex tachycardia, and hypotension; with intracavernosal use, priapism and (over time) fibrosis are risks shared with combination injection therapy. Compounded oral, injectable, and topical phentolamine products for sexual use are off-label/not FDA-approved formulations.

References

• Goldstein, Int J Impot Res 2000 (oral phentolamine pharmacology and phase 3 results)
• Seyam et al., Int J Impot Res 2005 (Tri-Mix dose-optimization vs PGE1)