Erectile Dysfunction: Cialis, Viagra and Levitra to Treat ED

From: webmd

Erectile Dysfunction: Cialis, Viagra and Levitra to Treat ED
There are only three oral drugs approved by the FDA to treat erectile dysfunction: Cialis, Levitra, and Viagra. All work by increasing the flow of blood into the penis so that when a man is sexually stimulated, he can get an erection.

What Are the Differences Between Cialis, Levitra, and Viagra?
Cialis, Levitra, and Viagra work by a similar mechanism to cause erections. There are subtle differences in how long the drug works and how quickly it works. Levitra works a little longer than Viagra. They both take effect in about 30 minutes. With Levitra, the effects last for about 5 hours. With Viagra, the effects last approximately 4 hours.

Cialis works a bit faster (within about 15 minutes), and the effects last much longer -- up to 36 hours in some cases.

If One of These Drugs Isn't Effective for Erectile Dysfunction, Can I Try Another?
Yes, but because these drugs work the same way, it's unlikely that you'll have success with one if you've failed to achieve an adequate erection with another.

What Precautions Should I Take Before Taking One of These Drugs?
There are certain situations in which these drugs may not be safe to take. Before taking them, tell your doctor:

If you are allergic to any drugs, including Viagra or other ED medications.
About any prescription or nonprescription medications you are currently taking, including herbal and dietary supplements.
If you are scheduled for surgery, including dental surgery.
If you take nitroglycerin or a long-acting nitrate to treat chest pain. The combination of Cialis, Levitra or Viagra with these drugs can cause dangerously low blood pressure.

If you take alpha-blockers for blood pressure or prostate problems. The combination of Cialis or Levitra with these drugs can also cause dangerously low blood pressure.
In addition, always follow the directions on your prescription label carefully and ask your doctor or pharmacist to explain any part that you do not understand. Take these drugs exactly as directed. Do not take more or less or take it more often than prescribed by your doctor. Do not take these drugs more than once a day.

Who Should Not Take Cialis, Levitra or Viagra?
If you have suffered from a heart attack, stroke or life threatening arrhythmia (irregular heart rate) within the last 6 months you should discuss other options with your doctor. It is also advised to avoid these drugs if you have uncontrolled high or low blood pressure or if you experience chest pain with sex.

What Are the Side Effects of Cialis, Levitra and Viagra?
Side effects are not common but they can occur. Side effects can include:

Headache
Upset stomach or ‘ heartburn’
Flushing (feeling warm)
Nasal congestion
Changes in vision (color, glare)
Back pain (with Cialis)
Call your doctor if you experience severe forms of these symptoms or if they do not go away after 4-8 hours.
Warning
Call your doctor or seek emergency treatment immediately if you experience any of the following symptoms:

Rash
Painful erection
Prolonged erection (longer than 4 hours)
Fainting
Chest pain
Itching or burning during urination
Stop taking these medications and call a doctor or health care provider right away if you experience sudden or decreased vision loss in one or both eyes. A rare vision problem called NAION has been reported by a few men using these drugs. NAION (nonarteritic anterior ischemic optic neuropathy) causes a sudden loss of eyesight because blood flow is blocked to the optic nerve. People who have a higher chance for NAION include those who:
Are over 50 years old
Smoke
Have heart disease
Have diabetes
Have high blood pressure
Have high cholesterol
Have certain eye problems

How Should These Drugs Be Stored?
These drugs should be kept in its original container and out of reach of children. Store them away from excess heat and moisture (not in the bathroom). Discard any medication that has expired or is no longer needed.

From Emedexpert:Brief comparison

Viagra (sildenafil)
Levitra (vardenafil)
Cialis (tadalafil)

Pharmaceutical Form
25mg, 50mg, 100mg tablets
2.5mg, 5mg, 10mg, 20mg tablets
5mg, 10mg, 20mg tablets

Efficacy
84%
80%
81%

Onset of action
30 minutes (effect delayed if taken with food)
25 minutes (effect delayed by fatty meal)
16-45 minutes (effect NOT delayed by food)

Recommended dose
50 mg, the physician may adjust this dose to 100 mg or 25 mg, depending on the patient
10 mg, the physician may adjust this dose to 20 mg if 10 mg is insufficient 10 mg, the physician may adjust this dose to 20 mg if 10 mg is insufficient

Duration of action
4 to 5 hours
4 to 5 hours
36 hours

Food Interactions less effective if you eat a high-fat meal
less effective if you eat a high-fat meal
moderate-fat meal does not reduce its effectiveness
works without regard to what you eat