A man’s erection is caused when nitric oxide is released from local nerve endings, which initiates a chemical reaction that allows blood vessels to dilate, or expand. A protein called cyclic guanosine monophosphate (cGMP) and an enzyme called PDE 5 play important roles in helping create an erection. cGMP signals the muscles in the blood vessel walls to relax and fill with blood. The amount of blood flowing into these blood vessels must be strictly controlled, filling them to capacity but not to bursting. PDE 5 breaks down cGMP to prevent overstimulation of the blood vessels and to prevent excessive relaxation as well.
Problems start to occur when there is not enough cGMP present or if cGMP is broken down too quickly by PDE 5. In either case, the blood vessels don’t remain relaxed long enough to fill with a sufficient amount of blood to allow the penis to become erect, thus giving rise erectile dysfunction. Current erectile dysfunction drugs, such as Viagra, Cialis, Levitra, and Stendra, work by inhibiting or blocking the effect of PDE 5 and thus allowing cGMP to remain active longer which in turn makes it easier to both achieve and maintain an erection. For erectile dysfunction drugs to work, a man must be sexually aroused as this allows the body to release cGMP which allows the blood vessels to fill with blood.
Cialis is slightly different in chemical makeup than Viagra and Levitra, which are both essentially the same in chemical makeup. Foods, especially fatty foods, affect how Viagra, Levitra, and Stendra are absorbed by the body. When taken with food, these two erectile dysfunction medications are not absorbed into the body as quickly and maximum efficacy is thus reduced. Food does not affect the absorption or efficacy of Cialis. Alcohol has not been shown to have any effect on PDE 5 inhibitors, although alcohol use has been linked to erectile dysfunction. Men who experience erectile dysfunction may wish to refrain from alcohol use for this reason. The makers of Stendra recommend men not consume more than three alcoholic beverages when taking the drug.
Viagra, Levitra, Cialis, and Stendra do not act immediately. Most studies have shown that the medications have an onset of action between 30 and 60 minutes, but that rate varies between individuals. Prescribing information for Viagra suggests taking it 60 minutes prior to sexual activity, while information for Levitra recommends taking it 25 to 60 minutes prior to sexual activity. Prescribing information for Stendra recommends taking it 30 minutes prior to sexual activity. The prescribing information for Cialis recommends that men should wait 30 minutes prior to engaging in sexual activity. These published times were all arrived at using drug studies with different measuring metrics. There have been no studies to date that directly compare onset times of all four drugs in one clinical study.
Duration of effect varies among PDE 5 inhibitors. According to prescribing information, Viagra and Levitra have a duration effect of 4 to 5 hours, Stendra has a duration effect of up to 6 hours, and Cialis can last up to 36 hours. This broad window of duration time allows men with erectile dysfunction more freedom to choose when to participate in sexual intercourse. All three medications have been shown in clinical trials to be effective in the general population of men with erectile dysfunction, which means men of all ages experienced improvement in erectile dysfunction.
The use of PDE 5 inhibitors is not recommended by men who have had a stroke or myocardial infarction (heart attack) within the last 6 to 8 weeks or who have significantly low blood pressure, uncontrolled high blood pressure, unstable angina (chest pain), severe cardiac failure, severe liver impairment, or end-stage kidney disease requiring dialysis. Men taking PDE 5 inhibitors should not take nitrates with these medications as death can occur due to a sudden drop in blood pressure.
PDE 5 inhibitors are effective for men who experience erectile dysfunction due to physical causes. Men who experience erectile dysfunction due to psychological causes should seek the help of a licensed sex therapist or counselor because erectile dysfunction drugs will not always help these men. To help ease anxiety about erectile dysfunction, men experiencing this issue should have an open conversation with their sexual partners to help build trust and intimacy in their sexual relationships. A partner in the know may have ideas on ways to shift the focus from getting and maintaining erections to other pleasing sexual interactions.