Pharmacology Update
Avanafil Tablets (Stendra)
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD. Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; and Assistant Professor of Medicine, University of California, San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Drs. Elliott and Chan report no financial relationships relevant to this field of study.
A new selective phosphodiesterase type 5 (PDE5) inhibitor has been approved for treating erectile dysfunction (ED). Avanafil was developed by Mitsubishi Tanabe Pharma Corporation in Japan and is manufactured in Japan and marketed by Vivus, Inc., as Stendra.
Indication
Avanafil is indicated for the treatment of ED.1
Dosage
The recommended dose is 100 mg taken without regard to a meal about 30 minutes before sexual activity.1 The dose may be increased to 200 mg or reduced to 50 mg based on effectiveness or adverse events. When taken with a moderate CYP3A4 inhibitor, the dose should not exceed 50 mg. Avanafil should not be taken more than once in 24 hours.
Avanafil is available as 50 mg, 100 mg, and 200 mg tablets.
Potential Advantages
Avanafil is highly selective for PDE5, compared to sildenafil, and has a rapid onset of action.
Potential Disadvantages
The most frequently reported adverse events were headache, flushing, nasal congestion, nasopharyngitis, and back pain.1 Frequencies range from 1% to 10%. Avanafil is contraindicated in patients taking strong CYP 3A4 inhibitors or CYP inducers. Avanafil carries the same class contraindications and precautions as other PDE5 inhibitors, including the risk of sudden vision change or loss and sudden hearing loss.
Comments
Avanafil has a rapid onset of action with mean time to peak concentration of approximately 0.6 hours. This compares to approximately 1 hour for sildenafil 100 mg, 2 hours for tadalafil 20 mg, and is similar to 0.66 hours for vardenafil 20 mg.2 Its elimination half is approximately 1 hour the shortest of these agents. This compares to 4 hours for sildenafil and more than 17 hours for tadalafil. It also has high selectivity for PDE5 compared to PDE6 compared to sildenafil and vardenafil.2 Inhibition of PDE6 has been implicated in visual symptoms.3 The efficacy and safety of avanafil was evaluated in two Phase 3, placebo-controlled, 12-week clinical trials.1 Study 1 (TA-301) randomized subjects (n = 646) with ED to placebo, avanafil 50 mg, 100 mg, or 200 mg. The primary endpoints were improvement in the International Index of Erectile Function (IIEF) and Sexual Encounter Profile questionnaires (SEP2 and SEP3). SEP2 assesses successful vaginal penetration and SEP3 assesses the ability to successfully complete intercourse. Statistically significant IIEF improvements were seen with all three doses of avanafil compared to placebo. From a baseline of 12.4 to 12.7, avanafil increased the IIEF score by 5.4, 8.3, and 9.5 points for the three doses compared to 2.9 for placebo. From a baseline of 45% to 48%, avanafil showed an absolute mean increase in SEP2 by 18%, 27%, and 30%, respectively, compared to 7% for placebo. SEP3 (baseline 12-14%) improved by 28%, 43%, and 44% compared to 14%, respectively. Two-thirds to almost three-fourths of the men who attempted sexual intercourse within 15 minutes were successful.2 In study 2 (TA-302), diabetics with erectile dysfunction (n = 302) were randomized to placebo or avanafil 100 mg or 200 mg. The results were similar although there was a lower magnitude of improvement in IIEF and SEP3.1 Avanafil is being evaluated in patients with post-radical prostatectomy.
Clinical Implications
Avanafil is the newest PDE5 inhibitor approved for the treatment of ED. It is characterized by rapid onset and short duration of action, but no clear clinical advantages in terms of effectiveness or safety have been demonstrated.
References
1. Stendra Prescribing Information. Mountain View, CA: Vivus, Inc; April 2012.
2. Limin M, et al. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction. Expert Opin Investig Drugs 2010;19:1427-1437.
3. Laties A, Sharlip I. Ocular safety in patients using sildenafil citrate therapy for erectile dysfunction. J Sex Med 2006;3:12-27.
A new selective phosphodiesterase type 5 (PDE5) inhibitor has been approved for treating erectile dysfunction (ED). Avanafil was developed by Mitsubishi Tanabe Pharma Corporation in Japan and is manufactured in Japan and marketed by Vivus, Inc., as Stendra.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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