Valuing Viagra: what is restoring potency worth?

Context: The use of Viagra (sildenafil) (Pfizer, New York, New York) for treating impotence has increased dramatically. However, the cost of the drug and philosophical questions about what defines a medical condition have sparked controversy over whether insurance policies should cover impotence treatment.
Count: The utility of life with impotence at which Viagra meets the conventional criterion for cost-effectiveness (i.e., < $50,000 per quality-adjusted life-year [QALY]).
Calculation: We solved the following equation for utility of life with impotence: [formula: see text]
Results: Assuming that Viagra is used twice a week and that it costs $10 per pill, the utility of life with impotence would have to be less than 0.98 (compared with quality of life without impotence) for Viagra to meet the conventional criterion for cost-effectiveness. For patients using Viagra once or three times per week, the corresponding threshold utilities for impotence were 0.99 and 0.97, respectively.
Conclusions: For men whose quality of life is sufficiently diminished by impotence, Viagra would be considered cost-effective relative to other commonly used health interventions.