This drug is a type 5 phosphodiesterase (PDE5) inhibitor. Oral administration of this drug can effectively improve the quality and duration of erection, and improve the success rate of sexual life in men with erectile dysfunction. The initiation and maintenance of penile erection is related to relaxation of cavernose smooth muscle cells, and cyclic guanosine phosphate (cGMP) is the mediator of relaxation of cavernose smooth muscle cells. This drug prevents the breakdown of cGMP by inhibiting phosphodiesterase type 5, resulting in the accumulation of cGMP, relaxation of the smooth muscle of the spongy body, and erection of the penis. Compared with phosphodiesterase isoenzyme 1, 2, 3, 4, 6, this drug has high selectivity to phosphodiesterase type 5. Data showed that its selectivity and inhibitory effect on phosphodiesterase type 5 were superior to other phosphodiesterase type 5 inhibitors, and it was speculated that this selectivity might lead to fewer cardiovascular and visual adverse reactions than other phosphodiesterase type 5 inhibitors.
The absolute bioavailability of oral tablets was 15%, and the peak time was 1h(0.5-2h) on average. The average peak time was 0.9h and 0.7h, respectively. The average peak blood concentration was 9µg/L and 21µg/L, respectively, and the efficacy duration was up to 1h. The protein binding rate of this drug is about 95%, 1.5h after a single dose of 20mg, the drug content in semen is 0.00018% of the dose. Drugs are mainly metabolized by cytochrome P450(CYP)3A4 in the liver, and a small number of drugs are metabolized by CYP 3A5 and CYP 2C9 isoenzymes. The main metabolite is M1 formed by the deethyl formation of piperazine structure. M1 also inhibits phosphodiesterase 5 (accounting for about 7% of the total efficacy), and its blood concentration is about 26% of the maternal blood concentration, and can be further metabolized. The excretion rate of drugs in the form of metabolites in feces and urine was about 91% ~ 95% and 2% ~ 6%, respectively. The overall clearance rate is 56L per hour, and the half-life of both parent compound and M1 is about 4 ~ 5h.
1. With the inhibition of CYP 3 a4 drugs (such as example, the wei, indiana that wei, ShaKui that wei, ketone health zun, itraconazole, erythromycin, etc.) with you, can inhibit the medicine in the liver metabolism, make the blood drug concentration increases, longer half-life, adverse reactions, such as low blood pressure, visual changes, headache, facial blushing, priapism) incidence increased. This drug should be avoided in combination with ritonavir and indonavir. When combined with erythromycin, ketoconazole, itraconazole, the maximum dose of this drug shall not exceed 5mg, ketoconazole, itraconazole dose shall not exceed 200mg. 2. Patients taking nitrate or receiving nitric oxide donor treatment should avoid the combination of this drug, its mechanism of action is to further increase the concentration of cGMP, resulting in enhanced antihypertensive effect and accelerated heart rate. Concomitant use with alpha blockers may enhance the antihypertensive effect and lead to hypotension. Therefore, it is prohibited for those who are taking alpha blockers. Medium fat diet (30% calories from fat) had no significant effect on the pharmacokinetics of 20mg, while high fat diet (more than 55% calories from fat) prolonged the peak time of the drug and reduced the peak plasma concentration of the drug by about 18%.