To understand why ED medication works the way it does, it helps to know what an erection actually is. It is a hydraulic event controlled by chemical signals. PDE5 inhibitors do not create the signal. They just stop the body from switching it off too quickly.

The Erection, Step By Step

  1. You see, hear, think, or feel something arousing.
  2. The brain sends signals down the spinal cord to nerves in the pelvis.
  3. Those nerves release a substance called nitric oxide.
  4. Nitric oxide triggers production of a molecule called cGMP.
  5. cGMP relaxes the smooth muscle inside the penis. Blood vessels widen.
  6. Blood floods into spongy tissue called the corpora cavernosa.
  7. The tissue swells, presses against the veins that would drain it, and traps the blood in.
  8. You have an erection.

There is a separate enzyme, called phosphodiesterase type 5, or PDE5, whose job is to break down cGMP. PDE5 is the brake. Once stimulation ends, PDE5 ramps up, cGMP is broken down, blood drains, the erection subsides.

What PDE5 Inhibitors Do

PDE5 inhibitors do exactly what the name suggests. They block PDE5 from breaking down cGMP. With the brake released, cGMP stays around longer, the tissue stays relaxed longer, more blood gets in and stays in, and an erection that would otherwise be too brief or too soft becomes firmer and lasts.

The crucial point: the medication does not produce nitric oxide. It does not produce cGMP. It just stops the existing cGMP from being broken down. If there is no signal to start with, there is nothing for the medication to act on.

The headline PDE5 inhibitors do not cause erections. They allow erections to happen properly when the normal arousal signal is sent. Sexual stimulation is still required.

Why Sex Drive Matters

If you have low libido, ED medication can still help with the physical erection but it cannot make you want sex. This is why some men feel disappointed when they take a tablet but nothing happens. They were not aroused, and the medication needs arousal to do anything. If desire itself is the issue, that needs its own assessment.

Why Food Matters For Some Of Them

Sildenafil and vardenafil are absorbed in the small intestine, and a fatty meal slows their absorption considerably. Take sildenafil after a heavy braai and the peak level in your blood might be half what it would have been on an empty stomach, and it will take longer to get there. Tadalafil is largely unaffected by food, which is one of its practical advantages.

Why The Window Of Action Matters

Sildenafil and vardenafil have a half life of around four hours. They are in your system at useful levels for around four to five hours after onset. Tadalafil has a half life of around 17 to 18 hours, which gives a useful window of up to 36 hours. The difference matters for planning rather than for effectiveness in a given moment.

Get The Right Medication For Your Situation

An online consultation matches the medication to your goals and your medical history.

Start Consultation

What PDE5 Inhibitors Will Not Do

  • They will not increase libido
  • They will not delay ejaculation. They are not premature ejaculation treatments. See our PE page for that.
  • They will not produce an erection without sexual stimulation
  • They will not increase penis size
  • They will not cure underlying causes like diabetes, cardiovascular disease, or low testosterone. They treat the symptom.

Why Some Men Do Not Respond

Around three in ten men do not respond well to first line PDE5 inhibitors. Common reasons:

  • The dose is too low. Going from 50 to 100 mg of sildenafil often does the trick.
  • It was taken with too much food. Try on an empty stomach.
  • It was taken too soon or too late. Allow 60 minutes.
  • The user was not actually aroused. The medication needs the signal.
  • Alcohol blunted the effect.
  • The underlying cause is severe vascular damage or nerve damage where oral medication is not enough. Second line treatments are then appropriate.

Before switching medication, doctors usually want to know whether you have given the first one a fair trial in the right conditions. Most men who think the medication has failed have not had a proper trial.

Related Reading

Frequently Asked

No. PDE5 inhibitors work alongside sexual stimulation, not instead of it. Without arousal, the medication does very little.

30 to 60 minutes for most men on most PDE5 inhibitors. Taking with food can slow this down, particularly for sildenafil and vardenafil.

It restores normal erectile function. It does not produce supernormal erections. If your maximum without ED was a certain firmness, medication brings you back to that level, not beyond it.

Not in a chemical sense. PDE5 inhibitors are not addictive. Some men do develop a psychological reliance, particularly if they used the medication to break a performance anxiety cycle. That is something a doctor can work through with you.