Generic Cialis is a PDE5 inhibitor class medication that is administered orally and used in the treatment of erectile dysfunction(ED). It works by inhibiting the action of the PDE5 enzyme that controls the amount of blood flowing into and leaving the penis when sexually aroused. This medication falls into the same class of drugs as other PDE5 inhibitors such as sildenafil and vardenafil. Erectile dysfunction, also sometimes referred to as impotence, can be defined as the inability to achieve or maintain an erection during sexual intercourse. This medication, nicknamed the “the weekend pill”, has a 36 hour effectiveness duration when used on an ‘as needed’ basis. This is the third most prescribed medication for ED, after sildenafil and vardenafil.
History of Tadalafil
Tadalafil was originally developed through a joint venture between the pharmaceutical company Eli Lilly and ICOS, who specialize in biotechnology. It was approved by the Food and Drug Administration (FDA) for sale in the United States in December of 2003 as a treatment for erectile dysfunction in men. Tadalafil is the only one of the three medications currently used to treat ED that has been approved for use as a once daily dosage in addition to being used on an as needed basis. The advantage that this drug can claim over sildenafil and vardenafil is the fact that it is structurally different. This allows it to have a 17.5 hour half-life as opposed to the 4.5 hour half-life of sildenafil and vardenafil. This means that half of the original quantity of the drug remains active in the body after 17.5 hours, causing one’s body to benefit from it for a longer period of time. Tadalafil is also presently under regulatory review in many regions for the use in the treatment of pulmonary arterial hypertension. In November of 2008, Eli Lilly sold the rights to United Therapeutics to market tadalafil in the United States as a medication for the use in pulmonary arterial hypertension for a payment of $150 million USD.
How Tadalafil Works
All PDE5 inhibitors act on a particular enzyme in the body which controls penile blood flow. Tadalafil’s distinction from other PDE5 inhibitors is its prolonged duration of activity in the body. PDE5 inhibitors act on the blood vessels in the penis by relaxing them and allowing increased blood flow. When a man becomes sexually aroused, nitric oxide is released from the nerves. This causes the chemical cyclic GMP to be released which relaxes the blood vessels in the penis, allowing increased blood flow into the spongy tissue of the penis. This lets the penis become full of blood which results in an erection. The enzyme phosphodiesterase type 5 (PDE5) is released after climax to break down the cGMP, permitting the penis to return to normal. By inhibiting the release of PDE5, cGMP remains active for a longer period of time which results in a longer erection.
Tadalafil Uses
Erectile Dysfunction
Tadalafil is currently used to treat sexual dysfunction in men from either erectile dysfunction or impotence. ED is the inability to either get or maintain and erection during some type of sexual stimulation or sexual intercourse. Some estimates show that anywhere from 15 to 30 million men are affected by some type of sexual dysfunction. There are several reasons that ED or impotence occurs. Some forms are causes by physical disorders, diseases like diabetes or physical injuries. There are other forms that can be caused by lowered libido, such as the types caused by antidepressant or use. There are also other medications which may contribute to or actually cause ED or impotence like the use of amphetamines. It is estimated that anywhere from 15 to 30 million men are affected by some form of sexual dysfunction.
Pulmonary Arterial Hypertension
Lilly finished their clinical trials and submitted the information for review to the comparable agencies in the United States, the European Union, Japan, Mexico and Canada. They did this late in 2008 and are waiting to learn whether their drug will be approved for the treatment of pulmonary arterial hypertension. The belief is that since tadalafil only targets selected areas for vasodilation (opening of the blood vessels), that it’s beneficial to those patients who do not need lowered blood pressure throughout their entire body. By doing this, the right ventricle of the heart has a decreased workload. The clinical trials suggest that this information is correct and that it would be beneficial to use in people with pulmonary arterial hypertension.
Side Effects of Tadalafil
The most frequent and common side effects associated with the use of tadalafil are:
- Headache
- Muscle aches
- Indigestion
- Flushing
- Stuffy nose
Rare but possible side effects of Tadalafil
- Unexplained rash
- Chest pains or arrhythmia
- Sudden hearing loss
- Sudden vision loss
- Blurred vision
- Erection lasting for more than 6 hours
- Painful erection
In May 2005, the FDA found that PDE5 inhibitors were associated with vision impairment or loss because of a condition known as non-arteritic anterior ischemic optic neuropathy (NAION). They found that most patients had certain underlying conditions which predisposed them to this condition. Nevertheless, in 2005 the FDA required that the labeling for all PDE5 inhibitors carry a more portentous warning for the risk of sudden vision loss and in 2007 they added an additional warning for the risk of sudden hearing loss.
Tadalafil Interactions
- Nitrates such as nitroglycerin, amyl nitrate, isosorbide and nitroprusside
- High blood pressure medications
- Antifungals such as ketoconazole and fluconazole
- Erythromycin
- Alcohol
- Grapefruit juice
- Herbal supplement St John’s Wort
Tadalafil Contraindications
- Nitrates should not be used within the first 48 hours after taking tadalafil. The use of amyl nitrate during this time may cause life-threatening low blood pressure.
- Tadalafil should not be used if the patient is suffering from kidney or liver disease.
- Inform your physician if there is a recent history of heart attack or stroke within the past 3 months
- If you have any allergies to tadalafil or any ingredient of it