Pharmacodynamics and pharmacokinetics of Cialis

Pharmacodynamics and pharmacokinetics of Cialis

Everybody is familiar with the effect provided by Cialis for ED treatment, however, not everyone knows how exactly this result can be achieved. Here you will be able to get acquainted with Cialis pharmacodynamics and pharmacokinetics.

What should you know about pharmacodynamics of Cialis

It is a reversible selective inhibitor of specific PDE5 cyclic guanosine monophosphate (cGMP). When sexual arousal causes local release of nitric oxide, the inhibition of PDE5 by Tadalafil leads to an increase in the level of cGMP in the cavernous body of the penis. The consequence of this is the relaxation of the smooth muscles of the arteries and the flow of blood to the tissues of the penis, which causes an erection. Cialis has no effect in the absence of sexual stimulation.

The effect of Cialis on PDE5 is more active than on other phosphodiesterases. Cialis is 10 times more active against PDE5 than in relation to PDE1, PDE2, PDE3, PDE4 and PDE7, which are localized in the heart, brain, blood vessels, liver, leukocytes, skeletal muscles and other organs. This selectivity for PDE5 in comparison with PDE3 is of great importance, since PDE3 is an enzyme involved in contraction of the heart muscle. In addition, Cialis is approximately 700 times more active with respect to PDE5 than with PDE6, found in the retina and is responsible for photo transfer. Therefore, the preparation does not cause changes in the recognition of blue / green colors. There is no Cialis influence on visual acuity, intraocular pressure, and pupil size.

Cialis also has a pronounced effect on PDE8, PDE9, PDE10 and PDE11. However, the physiological effects of inhibiting these enzymes have not been established.

Cialis improves the erection and the possibility of a successful sexual intercourse.

The drug acts for 36 hours. The effect is manifested as early as 16 minutes after taking the drug in the presence of sexual arousal, which is the obligatory condition of achieving the desired results. Cialis does not cause changes in testosterone, LH and FSH levels in the blood plasma.

There was no clinically significant effect of Cialis on sperm characteristics in men who used daily doses of the drug for 6 months.

Pharmacokinetics of Cialis

After oral administration, Tadalafil is rapidly absorbed from the digestive tract. The maximum effect is achieved on average after 2 hours. The speed and degree of absorption are independent of food intake. The time of taking the drug (morning or evening) does not affect the speed and degree of absorption.

The pharmacokinetics of Tadalafil in patients with erectile dysfunction is similar to the pharmacokinetics of the drug in individuals without erectile dysfunction.

The average VD is about 63 liters, which indicates that Tadalafil is distributed in the tissues of the body. In therapeutic concentrations, Tadalafil binding to plasma proteins is 94%. In healthy individuals, less than 0.0005% is found in the sperm.

  • Metabolism:

Metabolism takes place with the participation of the CYP3A4 isoenzyme. The main metabolite is methyl catechol glucuronide. The concentration of this metabolite is not clinically significant.

  • Excretion:

The average clearance of Tadalafil with oral administration is 2.5 l / h, and the average T1 / 2 is 17.5 h. Tadalafil is excreted primarily in the form of inactive metabolites, mainly with feces (about 61%) and, to a lesser extent, urine (about 36 %).

  • Pharmacokinetics in special clinical cases

In patients with mild and moderate hepatic insufficiency, pharmacokinetics is comparable to that of healthy individuals.