The Evolution of Erectile Dysfunction Drugs since Viagra Introduction Erectile dysfunction is the repeated condition where a male is not able to develop or maintain an erection firm enough for sexual intercourse. It is caused by both psychological and physiological factors. However, this condition is always treatable with drugs. ED as is commonly known varies in severity. For some men, it is a total inability to achieve an erection. Others have inconsistent ability to achieve one while others can only sustain brief erections. These variations make defining the condition and estimating its incidence difficult. Many men find it difficult and embarrassing to discuss their condition and thus the conditioned is under-diagnosed. Erectile dysfunction can occur at any age but is common among elderly men. Causes Erectile dysfunction occurs when there is a disruption in the normal erection process.