How Brand name Tadalafil Works to Treat Erectile Dysfunction 
The active ingredient in FDA approved Brand name Tadalafil is tadalafil. It works by increasing the blood flow to the penis when a man is sexually stimulated (if you aren't sexually excited, Brand name Tadalafil will not cause an erection). Once sexual activity is over, blood flow to the penis returns to normal and the erection goes away.

Brand name Tadalafil blocks an enzyme, PDE5, that can neutralize the body's natural erection-producing chemicals. So if that enzyme is put out of action, your body is able to freely produce the substances that induce an erection.

Brand name Tadalafil comes in doses of 5 mg, 10 mg, and 20 mg. For most men, the recommended starting dose is 10 mg.
 

Brand name Tadalafil Side Effects and Safety
Side effects of Brand name Tadalafil are described as mild to moderate and may include the following:

Headache
Upset stomach
Backache
Achy muscles
Stuffy or runny nose
Dizziness
Flushing
Brand name Tadalafil should not be used if you take nitrates or have certain heart diseases. If you have a liver or kidney condition, talk to your doctor before taking Brand name Tadalafil as you may need a different dosage.
Always ask your physician before taking Brand name Tadalafil or any other erectile dysfunction treatment.
 

Who Can Use Brand name Tadalafil
The Eli Lilly company, which makes Brand name Tadalafil, recommends you not take Brand name Tadalafil if you use medications called nitrates, if you are allergic to the active ingredient tadalafil, if you use recreational drugs called "poppers", or if you have been advised by your doctor not to engage in sexual activity for health reasons such as a weak heart.
 

How To Use Brand name Tadalafil
Take Brand name Tadalafil (tadalafil) exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.
Take each dose with a full glass of water.
Brand name Tadalafil (tadalafil) is usually taken when needed before sexual activity. The effects of Brand name Tadalafil (tadalafil) may last for up to 36 hours or more. Your doctor will determine how often you can take Brand name Tadalafil (tadalafil). Do not take
Brand name Tadalafil (tadalafil) more often than is directed by your doctor. Brand name Tadalafil (tadalafil) can help achieve an erection when sexual stimulation occurs. An erection will not occur just by taking a pill.
Brand name Tadalafil (tadalafil) can be taken with or without food.
Brand name Tadalafil (tadalafil) should not be taken with excessive amounts of alcohol (e.g. 5 or more drinks). Excessive alcohol may increase the risk of headache, dizziness, increased heart rate, or low blood pressure when Brand name Tadalafil (tadalafil) is take
If you develop dizziness, nausea, or angina (pain, tightness, discomfort, numbness, or tingling in the chest, arms, neck, or jaw) during sexual activity, refrain from further sexual activity and notify your doctor.
Contact your doctor or seek emergency medical attention for any erection that lasts longer than 4 hours. A sustained erection can damage the penis.
Grapefruit and grapefruit juice may interact with Brand name Tadalafil (tadalafil). The interaction could lead to potentially adverse effects. You should discuss the use of grapefruit and grapefruit juice with your doctor. Do not increase or decrease the amount of grapefruit products in your diet without first talking to your doctor.
Store this medication at room temperature away from moisture and heat