Why is Tadalafil prescribed?
Tadalafil is an oral drug for male impotence, also known as erectile dysfunction (ED). It works by dilating blood vessels in the penis, allowing the inflow of blood needed for an erection.
Most important fact about Tadalafil
Tadalafil causes erections only during sexual excitement. It does not work in the absence of arousal and does not increase sexual desire.
How should you take Tadalafil?
Take one Tadalafil tablet before sexual activity, with or without food. The best time to take Tadalafil depends on how and when the drug works for you, but some men are able to have an erection 30 minutes after taking it. Others are able to wait up to 36 hours after taking Tadalafil before engaging in sexual activity.
--If you miss a dose...
Take Tadalafil only before sexual activity, but no more than once a day. Do not take two doses at once.
--Storage instructions...
Store at room temperature.
What side effects may occur?
Side effects cannot be anticipated. If any develop or change in intensity, tell your doctor as soon as possible. Only your doctor can determine if it is safe to continue using Tadalafil.
• More common side effects may include:
Arm and leg pain, back pain, flushing, headache, indigestion, muscle aches, nasal congestion
This side effects list is not complete. If you have any questions about side effects you should consult your doctor. Report any new or continuing symptoms to your doctor right away.
Why should Tadalafil not be prescribed?
Do not take Tadalafil if you are taking any nitrate-based drug, including nitroglycerin patches (Nitro-Dur, Transderm-Nitro), nitroglycerin ointment (Nitro-Bid, Nitrol), nitroglycerin pills (Nitro-Bid, Nitrostat), and isosorbide pills (Dilatrate-SR, Isordil, Sorbitrate). This also includes street drugs known as "poppers," including amyl nitrate and butyl nitrate. Combining Tadalafil with any of these drugs can cause a dangerous drop in blood pressure.
Likewise, do not take Tadalafil with certain blood pressure and prostate drugs known as alpha-blockers, including Cardura (doxazosin), Hytrin (terazosin), Minipress (prazosin), and Uroxatral (alfuzosin). However, you can take the alpha-blocker Flomax (tamsulosin) at a dose of 0.4 milligrams once a day.
If Tadalafil gives you an allergic reaction, do not use it again.
Special warnings about Tadalafil
If you have heart problems severe enough to make sexual activity a danger, you should avoid using Tadalafil. If you take Tadalafil and develop cardiac symptoms (for example, dizziness, nausea, and chest pain) during sexual activity, do not continue. Alert your doctor to the problem as soon as possible.
Because Tadalafil has not been studied in people with cardiovascular disease, it's best to avoid Tadalafil if you've had a stroke or heart failure within the past 6 months, or a heart attack within the past 3 months. Be equally cautious if you have severe high or low blood pressure, heartbeat irregularities, or unstable angina (crushing heart pain that occurs at any time). If you develop angina after taking Tadalafil, seek medical attention immediately.
If you have severe kidney or liver problems, a bleeding disorder, stomach ulcer, or an inherited retinal disorder such as retinitis pigmentosa, use Tadalafil with caution. Its safety under these circumstances has not yet been studied.
Rare cases of prolonged and sometimes painful erections (known as priapism) have been reported with drugs similar to Tadalafil. If you develop an erection that lasts more than 4 hours, seek medical treatment immediately. Otherwise, permanent damage and impotence could result.
If you have a condition that might result in long-lasting erections, such as sickle cell anemia, multiple myeloma (a disease of the bone marrow), or leukemia, use Tadalafil with caution. Also use caution if you have a genital problem or deformity such as Peyronie's disease.
Remember that Tadalafil offers no protection from transmission of sexually transmitted diseases, such as HIV, the virus that causes AIDS.
Possible food and drug interactions when taking Tadalafil
Be sure to check with your doctor about the medications that should never be taken with Tadalafil, including:

Alpha-blocking drugs prescribed for high blood pressure or prostate problems, including doxazosin (Cardura), terazosin (Hytrin), prazosin (Minipress), and alfuzosin (Uroxatral)
Nitrate-based drugs prescribed for chest pain, such as nitroglycerin patches (Nitro-Dur, Transderm-Nitro), nitroglycerin ointment (Nitro-Bid, Nitrol), nitroglycerin pills (Nitro-Bid, Nitrostat), and isosorbide pills (Dilatrate-SR, Isordil, Sorbitrate)
Street drugs known as "poppers," including amyl nitrate and butyl nitrate
Tadalafil could intensify the effects of certain drugs used to lower blood pressure. Be sure to tell your doctor if you take any of the following:

Angiotensin II receptor blockers, such as candesartan (Atacand), eprosartan (Tevetan) and irbesartan (Avapro)
Bendrofluazide
Enalapril (Vasotec)
Metoprol (Lopressor)
If Tadalafil is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining Tadalafil with the following:

Other impotence drugs including alprostadil (Caverject), sildenafil (Viagra), and vardenafil (Levitra)
Erythromycin (E-Mycin, Ery-Tab, PCE)
Grapefruit juice
Indinavir (Crixivan)
Itraconazole (Sporanox)
Ketoconazole (Nizoral)
Rifampin (Rifadin, Rimactane)
Ritonavir (Norvir)
It's best not to drink too much alcohol while you're taking Tadalafil. Combining the two could lower your blood pressure and cause dizziness, especially upon standing. Drinking five or more servings of alcohol could intensify this effect and also cause headache and rapid heartbeat.
Special information about pregnancy or breastfeeding
Tadalafil should not be used by women. Its effects during pregnancy and breastfeeding have not been studied.
Recommended dosage
ADULT MALES
Doses range from 5 milligrams to 20 milligrams, depending on the drug's effect. The recommended starting dose is 10 milligrams.
Take Tadalafil only before sexual activity. The manufacturer recommends a maximum of one dose per day. If you're taking certain drugs that affect the liver, such as ritonavir (Norvir) or ketoconazole (Nizoral), the maximum recommended dose is 10 milligrams no more than once every 3 days.
If you have moderate kidney impairment, the recommended starting dose is 5 milligrams once a day, up to a maximum of 10 milligrams once every 2 days. If you have severe kidney impairment or need dialysis, the maximum recommended dose is 5 milligrams once a day. No dosage adjustment is required if you have mild kidney problems.
If you have mild or moderate liver impairment, your total daily dose should not exceed 10 milligrams once a day. If your liver is severely impaired, you will not be able to use Tadalafil.
Overdosage
Large doses of Tadalafil (up to 500 milligrams) resulted in similar side effects as regular doses. However, any medication taken in excess can have serious consequences. If you suspect an overdose, seek medical attention immediately.