Highlights
- The half-life of Viagra determines how long it works to boost your erections.
- PDE5 inhibitors like sildenafil (Viagra) are active during the first part of their half-lives.
- Cialis has a longer half-life than the other FDA-approved PDE5 inhibitors.
- Some patients may experience a longer sildenafil half-life than others.
The half-life of Viagra is approximately four hours. That’s how long it takes your body to eliminate half of its active ingredients. It means that your Viagra boosts your erections for four hours; after that, its erection-supporting effects slowly subside. [Español]
The Half-Life of Viagra and Other PDE5 Inhibitors
A drug’s half-life is the time it takes for 50 percent of the medication’s active ingredient to be eliminated from your bloodstream. It is also identical to the time during which the drug is effective.
In the case of Viagra, the half-life of sildenafil citrate, the little blue pill’s active ingredient, is roughly four hours, which means that the drug is effective for a similar period. An individual patient’s response to a drug can vary. Thus, in some cases, the medication’s half-life is most accurately expressed in a range of time rather than a specific number of hours.
In Viagra’s case, this time range is 3-5 hours. The body absorbs sildenafil citrate quickly. Within an hour of taking the blue pill, you will have achieved peak plasma concentration, or the amount of the drug that’s in your bloodstream.
If you have activities planned that require an erection on your part, take Viagra one hour before. Be aware, however, that the drug will continue boosting your erectile function for up to four hours.
Introduced in 1998, Viagra was the first of a family of drugs that came to be known as PDE5 inhibitors. They are specifically designed to treat erectile dysfunction caused by insufficient blood flow to the penis.
Other PDE5 inhibitors are Cialis, Cialis for daily use, Levitra, Staxyn, and Stendra. Here’s how the half-life of Viagra compares to that of other FDA-approved ED medications:
| Medication | Half-Life |
| Viagra (sildenafil) | 4 hours |
| Cialis (tadalafil) | 17.5 hours |
| Cialis for daily use (tadalafil) | 17.5 hours |
| Levitra (vardenafil) | 4-6 hours |
| Staxyn (vardenafil hydrochloride) | 4-6 hours |
| Stendra (avanafil) | 4-5 hours |
Levitra’s Half-Life is Slightly Longer
Levitra, the next of the PDE5 inhibitors to win approval by the Food and Drug Administration, has an average half-life of five hours, indicating that its duration of action is slightly longer than that of Viagra.
Vardenafil, the active ingredient in Levitra, is more active biochemically than sildenafil and a more selective PDE5 inhibitor. It takes less of the compound (20 milligrams) to achieve comparable effects. Vardenafil does not inhibit some of the biochemical compounds that sildenafil does, so it has fewer potential side effects. Its half-life is slightly superior to the sildenafil half-life as well.
The Half Life of Cialis is the Longest
Let’s compare that with the original formulation of Cialis, approved by the FDA in the fall of 2003, with a half-life of 17.5 hours.
The active substance in Cialis is tadalafil. Tadalafil is a more potent PDE5 inhibitor than sildenafil, so lower doses give the same effect.
Since it remains active for 17.5 hours, tadalafil is more suitable for men who are unsure when they’ll need their erections.
Cialis daily comes in lower doses than Cialis. It allows users to “load up” on tadalafil and take the drug daily to be ready for action around the clock. With Cialis daily, it takes up to five days to achieve blood concentrations comparable to a 20 milligram dose.
An added advantage is that fatty foods don’t interfere with tadalafil as they do with sildenafil.
Staxyn’s Half-life Slightly Exceeds Viagra’s
According to FDA prescribing information, Staxyn’s half-life is four to six hours, compared to Viagra’s three to five hours.
The active substance in this PDE5 inhibitor is vardenafil hydrochloride. Its effects are similar to those of Levitra, but the two drugs are not interchangeable. Staxyn provides higher systemic exposure to vardenafil than Levitra does.
Stendra Also Has a Longer Half-life than Viagra
The active substance in Stendra is avanafil. According to FDA prescribing information, the half-life of the drug is five hours.
Avanafil boosts erectile function as well as other PDE5 inhibitors. To achieve similar results, it’s taken in higher doses of 100 or 200 milligrams.
Active Half and Elimination Half
The first half of a drug’s half-life is sometimes referred to as the active half, meaning that the drug is most potent and effective during that period.
The second half of a drug’s half-life is known as the elimination half and refers to the time it takes for the body to flush out all traces of the drug’s active ingredient.
Individual Responses Vary
Individual responses to a drug’s active ingredient vary, so these figures are averages. Individuals who are highly sensitive to a drug’s effects might find that they feel the medication’s effects beyond its official half-life.
For example, many men who take the original, as-needed formulation of Cialis (tadalafil) have reported that the drug’s effects last for up to 36 hours, slightly more than twice the drug’s half-life, earning Cialis the nickname of the “weekend drug.”
Other drugs may also interfere with PDE5 inhibitors. Some can prolong their half-lives significantly.
The Practical Significance of a Drug’s Half-life
Scientifically determined half-lives of medications determine the dosage instructions, particularly for drugs needed to stabilize heart rhythms, blood pressure, and pain management. Because Viagra and the other PDE5 inhibitors lower blood pressure and can interact adversely with other hypotensive medications, you should not take one more than once in 24 hours.
Never exceed your doctor’s dose recommendation if you treat your ED with PDE5 inhibitors.
If you regularly use Viagra, its generic equivalent, sildenafil, or other PDE5 inhibitors, look into the convenience of ordering those drugs online from a trustworthy online facilitator.
eDrugstore Carries Viagra, Cialis, and their Generics
In business since the late 1990s, eDrugstore is a trusted online supplier of FDA-approved medications. Our in-house, U.S.-licensed doctors provide free medical consultations and the prescription you need for your erectile dysfunction medication.
Place your order now. We deliver quickly and discreetly, and shipping is always free.
James West is a seasoned health and wellness writer with a focus on topics related to physiology, sleep, and men’s health. He has contributed articles on a range of subjects, from erectile dysfunction treatments and sleep aids to hair loss, providing well-researched insights to help readers make informed health decisions.