Last reviewed 2026-04-20 · How we verify

Stendra (AVANAFIL)

Stendra works by inhibiting an enzyme that breaks down a molecule called cyclic GMP, allowing blood vessels to relax and improve blood flow to the penis.

Stendra (Avanafil) is a phosphodiesterase 5 inhibitor, a small molecule developed by VIVUS and currently owned by Vivus LLC. It targets cGMP-specific 3',5'-cyclic phosphodiesterase, which is involved in the regulation of smooth muscle tone in the corpus cavernosum. Stendra is FDA-approved for the treatment of impotence and is available as a generic medication. As an off-patent medication, it is no longer protected by active patents. Key safety considerations include potential interactions with nitrates and caution in patients with cardiovascular disease.

At a glance

Mechanism of action

The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cGMP, producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Avanafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of NO by inhibiting PDE5, which is responsible for degradation of cGMP in the corpus cavernosum. Because sexual stimulation is required to initiate the local release of nitric oxide, the inhibition of PDE5 has no effect in the absence of sexual stimulation.Studies in vitro have shown that avanafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (greater than 100-fold for PDE6; greater than 1,000-fold for PDE4, PDE8 and PDE10; greater than 5,000-fold for PDE2 and PDE7; greater than 10,000-fold for PD

Approved indications

• Impotence

Common side effects

• Headache
• Flushing
• Nasopharyngitis
• Nasal congestion
• Back pain
• Upper respiratory infection
• Dizziness
• Electrocardiogram abnormal
• Nausea
• Diarrhea

Drug interactions

• Vasodilators Organic Nitrates

Key clinical trials

• Daily Avanafil for Erectile Dysfunction (PHASE4)
• Avanafil Versus Sildenafil in Spinal Cord Injury Erectile Dysfunction (PHASE4)
• This Study is to Evaluate the Safety and Efficacy of Avanafil in the Treatment of Erectile Dysfunction. (PHASE3)
• Efficacy and Tolerability Study of Avanafil in Russia (PHASE3)
• Study Evaluating the Effects of Avanafil on Semen Parameters (PHASE4)
• Efficacy and Safety of Avanafil in the Patients With Erectile Dysfunction (PHASE2)
• Safety Study Looking at the Effects of Stendra on Vision (PHASE4)
• Research Evaluating a PDE5 Inhibitor for Erectile Dysfunction (PHASE4)

Primary sources

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