Tadalafil is an oral medication used to treat erectile dysfunction (ED) in men. It may be taken only when sexual intercourse is anticipated, or at a lower dose daily, if regular sexual intercourse is expected. The drug is a phosphodiesterase type 5 inhibitor (PDE5 inhibitor). This class includes other drugs such as sildenafil and vardenafil.
Erectile dysfunction, or impotence, affects many men and may be due to numerous factors, both physiological and psychological. The physiological process of attaining and maintaining an erection is a complex one and involves various chemicals and nervous system signals. Cyclic GMP is one of the chemical messengers involved. When sexual stimulation occurs, cGMP is released and it causes dilatation of the blood vessels in the penis, allowing more blood to flow into it and causing it to become rigid.
Phosphodiesterase type 5 is another chemical messenger that breaks down cGMP. Tadalafil, by blocking the phosphodiesterase type 5, prevents the breakdown of cGMP. This allows for a sustained erection. The drug will only work if sexual stimulation has occurred, as cGMP is only present then.
Tadalafil can be used on an "as needed" basis. When it is used in this way, the tablet is taken about half an hour before anticipated sexual intercourse. Usually the prescribing doctor will start at a lower dose of 10mg and increase it to 20mg, if necessary, based on response and tolerance.
Erectile dysfunction can be a distressing condition and cause a considerable amount of anxiety. Tadalafil may also be taken as a daily dose, if regular intercourse is expected, thus removing the need for an anticipatory dose. When used daily, though, the dose is much lower, at either 2.5mg or 5mg, depending again on response and tolerance.
As with any medication, tadalafil may interact with other medications or medical conditions. It must not be used in combination with any nitrate medication, a drug often used in angina patients. Any concomitant medication or diseases must be discussed with the prescribing doctor before using tadalafil to prevent any potentially dangerous interactions.
Tadalafil may cause side effects. The most common of these are dizziness, headache and postural hypotension, especially in patients taking antihypertensives concomitantly. Due to the possibility of dizziness, patients should not drive or work with heavy machinery after taking the drug. Rarely, priapism may occur. This refers to an erection lasting over four hours and requires medical attention to prevent long-term damage to the tissues of the penis.
