Erectile dysfunction is a treatable issue, and such medications as avanafil (Stendra), sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra) can help.

Phosphodiesterase type 5 (PDE5) inhibitors impede the functioning of PDE5, an enzyme in blood vessel walls that helps control blood flow.

Following arousal, the body releases enzymes that cause smooth muscle in blood vessels to relax, allowing for more blood to flow through. PDE5 inhibitors block the degradation of these enzymes, increasing blood flow and resulting in an erection.

It is important to note that a person needs to be aroused for a PDE5 inhibitor to help with ED.

PDE5 inhibitor drugs for treating ED include:


Sildenafil (Viagra) can be an effective way of treating ED, and it can also treat conditions such as high blood pressure. The pills come in doses of 25 milligrams (mg), 50 mg, or 100 mg.

Some advantages of taking Viagra for ED include:

  1. Viagra is fast-acting, it starts working around 30 minutes after taking the pill.
  2. The effects have been well-established in many clinical trials.
  3. The effects can last for up to 4 hours.

Serious side effects are rare — though they can include allergic reactions and heart problems.
Some disadvantages include:

It may only be a short-term option, as 20–50% of people who take Viagra do so temporarily.
It may not be suitable for people with some chronic conditions, such as multiple sclerosis, a 2012 review reports.

Viagra can interact with other drugs, including some heart disease and blood pressure medications.
People seem to prefer an alternative, Cialis, though the two drugs are equally effective, according to 2017 research.


Tadalafil (Cialis) also works by increasing blood flow to the penis.

Doctors also use Cialis to treat high blood pressure in the lungs and enlargement of the prostate. For ED, people take it as an oral tablet.

Some advantages of Cialis include:

  1. Cialis is the longest-lasting PDE5 drug for ED, typically lasting up to 36 hours, though some reports suggest that it can last up to 72 hours.
  2. It is possible to take a low dose of Cialis — 2.5 mg to 5 mg — once a day, so it can be a longer-term solution.
  3. People who regularly engage in sexual activities may prefer taking a daily pill.

Research suggests that people who take Cialis experience more sexual confidence than those who take Viagra.

Disadvantages include:

  1. Taking Cialis daily can be expensive.
  2. Taking it in the long term may prevent or delay treatment for the underlying cause of ED, which can be psychological.
  3. Cialis can interact with several types of medication, including common blood pressure drugs.


Avanafil (Stendra) is another PDE5 drug. Unlike Cialis and Viagra, Stendra is not available in generic form. It works like other drugs in its class by increasing blood flow to the penis.

Some advantages of Stendra include:

  • Stendra can start working 15 minutes after taking the drug.
  • Research has found that Stendra is a safe and effective ED treatment.
  • The effects can last for up to 6 hours.

A 2014 review found that older and younger adults both preferred taking Stendra to other PDE5 drugs, due to its quick effects.

Disadvantages include:

Because Stendra is not available in generic form, it can be more expensive than other PDE5 drugs.


Vardenafil (Levitra), like other PDE5 medications for ED, works by increasing blood flow to the penis.

Some advantages of Levitra include:

  1. Clinical trials have found it to be effective.
  2. Unlike Stendra, Levitra is available in a cheaper generic form.

Disadvantages include:

The drug can take comparatively longer to start working — a person takes it 1 hour before sexual activity.
Compared with Viagra and Cialis, Levitra does not have any unique advantages.

To ask any additional questions you can contact our team of experts and get a free consultation.