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What to Expect From Erectile Dysfunction Medication

What to Expect From Erectile Dysfunction Medication

Erectile dysfunction medications like sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra) are some of the most widely used prescription drugs on the market today.

They’re also some of the most well understood, with a huge number of studies observing direct effects, side effects, the average onset of action, half life and other important factors that affect how each medication affects the body.

Below, we’ve covered what you should expect from erectile dysfunction medication, from how long you should expect to wait before it takes effect to the side effects you could experience as a result of the medication. This article is for informational purposes only and you should talk to your primary care physician before starting an ED treatment program.

Onset of Action for ED Medications

Most erectile dysfunction drugs take 30 to 60 minutes to start working. The fastest-acting ED drug is tadalafil (widely known as Cialis), which usually begins to work within 30 minutes of consumption.

Sildenafil, or Viagra, should be taken approximately 60 minutes before sexual activity. Most of the time, a standard dose of sildenafil will begin to produce a noticeable effect between 30 and 60 minutes after it's consumed orally.

Finally, vardenafil, or Levitra, take action in about the same amount of time as sildenafil. Most manufacturers of vardenafil recommend taking the drug 60 minutes before sexual activity to give it time to begin working.

In general, you’ll need to provide some time for your ED medication to start working before you engage in sexual activity. The best approach is to prepare ahead of time and make sure you’ve consumed your ED medication 30-60 minutes before sex, depending on the specific drug and your doctor's recommendation.

It’s also important to remember that a high-fat, large meal can potentially delay the absorption of most ED medication. For this reason, most ED drug manufacturers recommend taking ED drugs such as sildenafil, tadalafil, and vardenafil with plenty of water on a relatively empty stomach.

Half-Lives of ED Medications

A drug’s half-life is the amount of time required for the concentration of the medication to fall to half of its peak concentration. For example, a 50mg dose of sildenafil (Viagra) will be reduced to approximately 25mg after one half-life.

The half-life of a medication determines how long it will remain active in the body. Generally, ED drugs still provide some effects after one half-life and gradually become less effective as they’re eliminated from the body and excreted.

Below, we’ve listed both the half-lives and duration of action for three of the most common ED drugs:

  • Sildenafil, or Viagra, has a half-life of 4 hours and remains active in the body as an effective erectile dysfunction treatment for 3 to 5 hours after it’s consumed.
  • Tadalafil, or Cialis, has a half-life of 17.5 hours and remains active in the body as an effective erectile dysfunction treatment for up to 36 hours after it’s consumed.
  • Vardenafil, or Levitra, has a half-life of 4 to 5 hours and remains active in the body for up to 6 hours after it’s consumed.

As you can see, tadalafil is by far the longest lasting of the three most popular ED medications currently on the market. This makes it a good option for periods where you need to consistently treat ED, whereas sildenafil and vardenafil are designed more for incidental use. It also has the added benefit of treating benign prostatic hyperplasia (BPH). Of course, using tadalafil for either or both ED and BPH should be discussed with your primary care physician.

Side Effects of ED Medication

Because most ED drugs work similarly, they also have similar side effects. The side effects of ED drugs typically occur while the drugs are active in the body, although they can often last for slightly longer than the drug itself.

This means that if you’re prone to side effects from ED drugs, you may notice them lasting for longer if you use a medication such as tadalafil, which has a very long half life.

There are seven side effects that are most commonly reported by ED drug users. They are:

  • Headaches*, which are associated with all ED drugs. Headaches are most commonly caused by increased nitric oxide levels, which can increase blood flow and result in a temporary headache.
  • Dizziness*, which is also a result of increased nitric oxide levels. The dizziness from ED medication is typically not severe, but it can potentially lead to discomfort and fainting in people with underlying health conditions.
  • Muscle aches, which may also be caused by the increase in blood flow caused by all widely available ED medications.
  • Nasal congestion, or a stuffy nose. This typically occurs when ED medications are at peak concentration and reverses as the drugs are metabolised and excreted.
  • Facial flush, which can range from mild facial redness to bright red skin that looks like it’s affected by a rash. Like other side effects, this usually reverses as the levels of the medication in your system decline.
  • Vision issues, including temporary blurry vision and blue-tinted vision. This condition is called cyanopsia and is thought to result from diminished enzyme activity.
  • Digestive issues, ranging from diarrhea to indigestion and bloating. These are usually temporary and can be made worse by consuming alcohol, caffeine, carbonated drinks and dairy products.

*These side effects are particularly important to watch for if you have other medical (heart) conditions that require you to take nitrates.

The Cost of ED Medication

The total cost of treating ED using commonly prescribed medications like sildenafil, tadalafil and vardenafil can vary depending on a variety of factors.

The first factor is the dosage you use. Most ED medications come in a range of doses, meaning that an effective dose for one person might not be equal to an effective dose for another person. Your primary care physician can help determine what dose you should use.

The second factor is the specific medication you choose. Sildenafil, tadalafil and vardenafil are all different medications available at different prices.

The third factor is the amount of medication that you use. If you use ED medication every day, the cost can quickly add up; if you take it once or twice per week, the total cost per year will be far lower.

The fourth factor is your insurance coverage. While some insurance policies do not cover the cost of ED medication, others do, making the cost of treating erectile dysfunction far lower.

Finally, a significant cost factor is the brand of medication you choose. Many ED drugs are available as branded medications such as Viagra, Cialis and Levitra and as far more affordable generic medications.

Learn More About ED Medication

Would you like to learn more about ED medication? Our guide to the most common erectile dysfunction treatments covers sildenafil, tadalafil and vardenafil in more detail, letting you get a complete understanding of the most widely used ED medications on the market today.

This article was reviewed by Ho Anh, MD.

Important Safety information


Do not take Sildenafil (sildenafil citrate) if you:

  • take any medicines called nitrates, often prescribed for chest pain, or guanylate cyclase stimulators like Adempas (riociguat) for pulmonary hypertension. Your blood pressure could drop to an unsafe level
  • are allergic to sildenafil, as contained in Sildenafil and REVATIO, or any of the ingredients in Sildenafil

    Discuss your health with your doctor to ensure that you are healthy enough for sex. If you experience chest pain, dizziness, or
nausea during sex, seek immediate medical help

    Sildenafil can cause serious side effects. Rarely reported side effects include:

  • an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away.
If it is not treated right away, priapism can permanently damage your penis
  • sudden vision loss in one or both eyes. Sudden vision loss in one or both eyes can be a sign of a serious eye problem called
non-arteritic anterior ischemic optic neuropathy (NAION). Stop taking Sildenafil and call your healthcare provider right away if you
have any sudden vision loss
  • sudden hearing decrease or hearing loss. Some people may also have ringing in their ears (tinnitus) or dizziness. If you have
these symptoms, stop taking Sildenafil and contact a doctor right away

    Before you take Sildenafil, tell your healthcare provider if you:

  • have or have had heart problems such as a heart attack,
irregular heartbeat, angina, chest pain, narrowing of the aortic valve, or heart failure
  • have had heart surgery within the last 6 months
  • have pulmonary hypertension
  • have had a stroke
  • have low blood pressure, or high blood pressure that
is not controlled
  • have a deformed penis shape
  • have had an erection that lasted for more than 4 hours
  • have problems with your blood cells such as sickle cell
anemia, multiple myeloma, or leukemia
  • have retinitis pigmentosa, a rare genetic (runs in families)
eye disease
  • have ever had severe vision loss, including an eye problem
called NAION
  • have bleeding problems
  • have or have had stomach ulcers
  • have liver problems
  • have kidney problems or are having kidney dialysis have any other medical conditions

    Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins,
and herbal supplements.

    Sildenafil may affect the way other medicines work, and other medicines may affect the way Sildenafil works, causing side effects.
Especially tell your healthcare provider if you take any of the following:

  • medicines called nitrates
  • medicines called guanylate cyclase stimulators such as Adempas (riociguat)
  • medicines called alpha-blockers such as Hytrin (terazosin
HCl), Flomax (tamsulosin HCl), Cardura (doxazosin
mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl),
 Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin).
Alpha-blockers are sometimes prescribed for prostate
problems or high blood pressure. In some patients, the use
of Sildenafil with alpha-blockers can lead to a drop in blood pressure or to fainting
  • medicines called HIV protease inhibitors, such as ritonavir (Norvir), indinavir sulfate (Crixivan), saquinavir (Fortovase or Invirase), or atazanavir sulfate (Reyataz)
  • some types of oral antifungal medicines, such as
 ketoconazole (Nizoral) and itraconazole (Sporanox)
  • some types of antibiotics, such as clarithromycin (Biaxin),
telithromycin (Ketek), or erythromycin
  • other medicines that treat high blood pressure
  • other medicines or treatments for ED
  • Sildenafil contains sildenafil, which is the same medicine found
in another drug called REVATIO. REVATIO is used to treat a
rare disease called pulmonary arterial hypertension (PAH).
 Sildenafil should not be used with REVATIO or with other PAH
treatments containing sildenafil or any other PDE5 inhibitors
(such as Adcirca tadalafil)

    Sildenafil does not protect against sexually transmitted diseases, including HIV.

    The most common side effects of Sildenafil: headache; flushing; upset stomach; abnormal vision, such as changes in color vision
(such as having a blue color tinge) and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash.


    Sildenafil (sildenafil citrate) is prescription medicine used to treat erectile dysfunction (ED).

    Sildenafil is not for women or children.