Most erectile dysfunction drugs go into effect within 15 to 60 minutes and remain effective for four to six hours. An exception is Cialis, which takes a little longer to become effective but remains so for up to 36 hours.

Introduction

Men who take an erectile dysfunction Drug to facilitate erection often select their preferred medication on the basis of its duration of action, or how long it remains effective.

The key to understanding a specific medication’s duration of action in the body is that drug’s half-life, or the length of time it takes for the body’s metabolic processes to reduce the body’s blood level of the drug to half its original strength.

For example, the blood level of a drug with a half-life of two hours falls to 50 percent at the two-hour mark, 25 percent at the four-hour mark, 12.5 percent at the six-hour mark, and just over 6 percent at the eight-hour mark.

During that initial two-hour period, the concentration of the drug’s active ingredient in the blood ranges from near 100 percent down to 50 percent. However, that’s a sufficient level of active ingredient to produce the desired results. Beyond that, the drug’s continued effectiveness depends on the patient’s sensitivity to the medication, as well as the magnitude of the health problem for which the drug is being taken.

Here’s a Look at Each ED Drug

Of the oral erectile dysfunction drugs now available in the United States, five brand-name medications are designed for use on demand. That is to say that these drugs are taken a short time before the anticipated start of sexual activity. They temporarily improve blood flow so that men whose vascular function is impaired can more readily get and keep an erection during the period the drug is effective.

High-strength Cialis is the slowest-acting of these on-demand ED drugs. Tadalafil, its active ingredient, reaches its maximal concentration in the bloodstream roughly 120 minutes after it’s taken. By contrast, sildenafil citrate and vardenafil hydrochloride, the active ingredients in Viagra and Levitra and Staxyn, respectively, Reach Maximal Concentration at about 60 minutes. The fastest acting of the on-demand ED drugs is avanafil, the active ingredient in Stendra, which reaches maximal concentration in 30 to 45 minutes.

The accompanying table shows the time its takes for each ED drug to reach maximal concentration in the bloodstream and the approximate level of the drug left in the blood at various intervals after it’s been taken.

As you can see from the table, there is little variation between Viagra, Levitra, Staxyn, and Stendra in terms of duration of action. However, Stendra does reach maximal concentration slightly faster than the other three.

The clear standout in terms of duration of action is Cialis on demand, which hasn’t quite reached its half-life at the 16-hour mark. In fact, its half-life is 17.5 to 18 hours, and its effectiveness is said to last for up to 36 hours, which has earned it the nickname “the weekend drug.”

Sildenafil Citrate (Viagra)

Introduced in 1998, Viagra was the first of the so-called PDE5 inhibitors to hit the market. Originally researched by Pfizer as a possible treatment for angina pectoris and hard-to-treat hypertension, sildenafil citrate failed to impress. However, it did produce a curious side effect in male participants in early clinical testing. Men taking the drug were able to get an erection with ease. Even those who’d been diagnosed as impotent suddenly found themselves able to get an erection once again. Pfizer abruptly took its sildenafil research in a new direction, and Viagra was its end result.

Viagra and its generic equivalent, sildenafil citrate, are both available in tablets of 25, 50, and 100 milligrams. The Recommended Starting Dose is 50 milligrams, which can be adjusted upward or downward as necessary.

Viagra’s first generic competition hit the American market in December 2017. Both Teva, the world’s largest generic drugmaker, and Greenstone LLC, a wholly owned subsidiary of Pfizer, introduced generic formulations of the drug at that time.

Vardenafil Hydrochloride (Levitra)

Approved by the U.S. Food and Drug Administration in August 2003, Levitra was the second PDE5 inhibitor available to American consumers. Its active ingredient is stronger than that of Viagra, thus necessitating lower doses to produce the desired effect. However, as sold to consumers, both Levitra and Viagra are very similar in terms of onset and duration of action.

Levitra and its generic equivalent, vardenafil hydrochloride, are available in tablets of 2.5, 5, 10, and 20 milligrams. The recommended starting dose is 10 milligrams, which can be adjusted either upward or downward as needed.

The first generic version of Levitra to go on sale in the United States debuted at the beginning of November in 2018. It is marketed by Zygus (USA), the U.S. division of Zygus Pharma, which is headquartered in India.

Tadalafil (Cialis)

Clearly the most long-lasting of the ED drugs available, Cialis and its generic equivalent, tadalafil, can remain effective for up to 36 hours. As approved by the Food and Drug Administration in the fall of 2003, Cialis was marketed exclusively as an on-demand drug until early 2008, when the FDA approved low-dose Cialis as a daily therapy. Taken faithfully every day, low-dose (2.5 or 5 milligrams) Cialis promises users that they can be ready for sexual activity whenever the moment is right. By its very nature, daily Cialis doesn’t fit into the matrix of on-demand ED drugs, which are the subject of our comparisons in this article.

Tadalafil, the generic equivalent of brand-name Cialis, made its debut in the fall of 2018. For use as an on-demand ED medication, the recommended starting dose of Cialis is 10 milligrams. However, if that fails to produce the desired results, users can increase their dose to 20 milligrams. Tablets of 2.5 and 5 milligrams are generally reserved for use as part of the daily therapy.

Vardenafil Hydrochloride (Staxyn)

Vardenafil hydrochloride, the active ingredient in Levitra, is also the active ingredient in Staxyn, which is the only one of the ED drugs that is orosoluble (dissolves quickly in the mouth and can be taken without water). While Staxyn might be marginally faster-acting than Levitra because of its unique form of administration, it is in most respects identical to Levitra.

While a generic equivalent of Levitra is available, as mentioned earlier, no generic equivalent of Staxyn is currently marketed, nor is one likely to be for at least the next few years. Staxyn is available in handy packets of orally disintegrating 10-milligram tablets.

Avanafil (Stendra)

Touted as a “next-generation” ED drug, Stendra won FDA approval in 2012 and was the last brand-name ED medication to debut on the American market. According to its manufacturer, its benefits over its competitors include not only somewhat faster action but fewer side effects.

Although it takes 30 to 45 minutes to reach maximal concentration in the bloodstream, anecdotal reports indicate that Stendra often takes effect in as little as 15 minutes. Its effects last up to eight hours, according to its manufacturer.

Available in tablets of 50, 100, and 200 milligrams, Stendra’s recommended starting dose is 100 milligrams. Its claim of fewer side effects than other ED drugs rests primarily on its more narrowly focused targeting of the phosphodiesterase-5 enzyme, which can impede erectile function, particularly in those whose vascular function is compromised. Other ED drugs target the PDE5 enzyme but also can interfere with the function of other PDE enzymes, including PDE1, PDE3, PDE6, and PDE11, triggering additional side effects.

Buying ED Drugs Online

Whatever ED drug best suits your needs, you may find that you can save both time and money by ordering from longtime online facilitator eDrugstore.com. Based in Tempe, Arizona, eDrugstore sells only FDA-approved medications, all of which are dispensed by licensed U.S. pharmacists.

In business since the late 1990s, eDrugstore stocks a full range of ED medications, including both brand-name and generic products. To learn more, visit its Erectile Dysfunction page.