Description
Viagra increases blood flow to the penis which helps men get and sustain an erection long enough for sex. The active ingredient in Viagra is sildenafil, which is known medically as a PDE5 inhibitor. Sildenafil inhibits (blocks) an enzyme which regulates blood flow in the penis.
PDE5 inhibitors multiply the natural process of arousal and increase blood flow to the penis in situations of sexual stimulation. Sildenafil helps to achieve an erection but relies on natural arousal as a trigger. It, and other PDE5 inhibitors such as tadalafil, vardenafil, and avanafil, support sexual relations when erections are failing.
How to take
The usual first starting dose of Viagra is one 50mg tablet, for men who have not used it before, although men over the age of 65 years would normally start on the lowest dose tablet (25mg).
Viagra works in 30 to 60 minutes after it is taken and usually remains active for 4 hours.
If 50mg strength of tablet is highly effective subsequent doses may be reduced down to one 25mg tablet. If a 50mg tablet is ineffective, or the duration of activity is less than 4 hours, the dose can be increased to one 100mg tablet. Do not take Viagra more than once per day, or more than 100mg dose.
Arousal is required for the treatment to work. Viagra is most likely to be suitable if taken in situations where sexual arousal is expected within an hour or two of taking the tablet. Without sexual arousal there will be no benefit and the effect of the tablet will simply wear off after about 4 hours.
Avoid large meals, meals high in fat, excessive alcohol, and grapefruit as these can affect efficacy (effectiveness).
