Viagra - the first and most popular development against erectile dysfunction. It is intended for men suffering from the inability to maintain an erection for an adequate time or of sufficient hardness. The medication assists with getting an erection in a natural way by increasing blood flow to the penis. According to research, Viagra solves problems with potency for more than 80% of men. Sildenafil is effective for dysfunction caused by physiological reasons, but not psychological (e.g. stress and depression).
The tablet takes effect in about an hour, and last for up to 4 hours.
The medication assists with getting an erection at the time it’s needed, with sexual stimulation. It is not a hormonal agent or pathogen. There is no negative effect on reproductive functions, and can be used daily. How does Viagra work? The effect is to increase blood flow to the genitals, which causes a natural erection.
Dosage:

Usually Viagra comes in dosages of 50mg and 100mg. The optimal dose is 50 mg and may be increased due to lack of effect; 100mg is the maximum daily dose.
How is it used?
Tablets should be taken approximately one hour before sexual intercourse. The effect starts half an hour to an hour after ingestion and lasts for up to four hours. A more rapid effect can be achieved by taking the pill before meals. This medication is only useful for the purpose of sexual intercourse.
Contraindications
The medication should be used with caution by people with cardiovascular disease; it should not be used by those suffering from anatomical deformations of the penis, peptic ulcer disease of the gastrointestinal tract, disorders of the liver, or severe renal insufficiency.
Even with long-term usage, not exceeding 100 mg per day, there was no evidence of any serious consequences. The drug does not harm a healthy body, and has no effect on fertility.