If Viagra Doesn’t Work, One Can Try Adding Metformin

An Argentinean study reported at the recent Endocrine Society meeting may give new hope to men with erectile dysfunction (ED) when Viagra® has failed to help. Seventeen men with Viagra-resistant ED were instructed to take metformin 1,700 mg daily, and Viagra (sildenafil) ‘on demand’. Thirteen men with the same problem were given a placebo daily, and took Viagra on demand.

Evaluations made at baseline and after 2 and 4 months included weight, waistline, basal metabolic index (BMI), blood glucose and insulin, and a recognized ED questionnaire score.

At baseline, the average ED scores were 14.3 in the metformin group and 15.2 with the placebo. After 2 months, they were 17 with metformin and 14.8 with placebo. And after 4 months, they were 19.8 with metformin and 15.8 with placebo. In addition, there was significant improvement in insulin resistance with metformin, compared with placebo. BMI and waist circumference declined significantly with metformin.

How does metformin help in this situation? Erectile function depends on the release of nitric oxide in the small blood vessels of the penis; Viagra works by blocking the breakdown of nitric oxide. Insulin resistance (a condition encountered in type 2 diabetes and pre-diabetes) can interfere with Viagra’s ability to block nitric oxide breakdown. And metformin, a useful anti-diabetic medication, in addition to other effects, increases insulin sensitivity.

The results of this study show that metformin has a role to play in helping Viagra, and other PDE5 inhibitors like Cialis® and Levitra®, to improve ED in selected men. A trial of metformin may be a useful approach in such cases, and can also lead the way to an early jump in the prevention of diabetes in a susceptible person.