An erection occurs when someone is stimulated by an erotic thought or sexual contact. The brain then commands nitric oxide be produced by the lining of blood vessels that then causes penis to be engorged with 6 times its normal the blood flow getting trapped in the penis. Without chemicals called phosphodiesterases, erections would last indefinitely. Now that’s undesirable walking around with a hard-on when it’s not wanted. They work at reversing the process that keeps the penis erect.

ED medications interfere with this exact chemical that allow blood to leave the penis. They inhibit or suppress the function of this chemical pushing the situation in favour of an erection. Men with erectile dysfunction benefit from having the chemicals that lead to erections outweigh the actions of the phosphodiesterases that cause the penis to go flaccid. 

That is exactly what the medications for erectile dysfunction do; they block, or inhibit, the phosphodiesterases (that’s why they are called phosphodiesterase inhibitors-PDE5 inhibitor).

CHOOSING THE RIGHT PDE5-INHIBITOR FOR YOURSELF WOULD DEPEND ON SEVERAL FACTORS

  1. Your existing medical conditions
    Any heart rhythm problems? Any sinusitis?

  2. Your existing medications
    Any blood pressure lowering tablets?

  3. Your preferred time of day for sex
    Just after waking up in the morning? Or after dinner? Or just before bed time?

  4. Side effects experienced with these medication?
    Eg. if side effects like headaches are experienced then you would want a medication that washes out of your system faster so the headaches don’t last so long

  5. How quick do you require the effect of the medication to kick in?
    do you have enough lead up time to sex?

  6. Do you prefer to have sex anytime of the day (spontaneous sex) without having to taken a medication 1 hour before intercourse?
    Then maybe you need to consider drugs like Cialis 5mg that is taken everyday regardless of whether you are having sex or not.

  7. How many times in a week you have sex?
    This would determine if you pick a medication that lasts longer in your system. For example Cialis 20mg lasts for 36 hours in your system, if you had sex today and you would like to have intercourse again the following day then you will not need to take the drug again as there is a sufficient dosage still in your system.

Time to
peak effect
Duration drug last
in system for
improved sexual function
Time for side
effects to
wash out of system
Can be taken
with food?
Spontaneity
of sex
Effect of
heart rhythm
Effect on facial
flushing/nasal congestion
Viagra ✓✓✓
within half to 1 hour
✓✓
6-8 hours

Side effects fade as quickly as
drugs leaves the bloodstream
✗✗
best on empty stomach

Does not allow for “on demand” sex
Levitra ✓✓✓
within half to 1 hour
✓✓
6-8 hours

Side effects fade as quickly as
drugs leaves the bloodstream

must avoid fatty food

Does not allow for “on demand” sex
✗✗
* can cause abnormal heart
rhythms by prolonging QT interval on heart tracing ECG
*not to be combined with
other drugs that prolong QT interval
Cialis ✓✓
sometimes 1-2 hours
✓✓✓

up to 36 hours

great for sex next day w/o taking another pill


Side effects can last ~30hrs
✓✓✓
effective regardless of type of food eaten
✓✓✓
Cialis 5mg formulation is a
once daily dosing – taken 1 pill every day à allowing for sex
anytime you please
** Cialis 20mg does not offer this

As side effects last longer nasal congestion and
stuffiness can last for up to 30hrs after taking pill

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