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Sildenafil Citrate Tablets

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Generic name: Sildenafil Citrate Tablets
Chinese Pinyin: GouYuanSuanXiDiNaFeiPian
English name: Sildenafil Citrate Tablets
Product name: Kingo
Ingredients: The main ingredient of this product is: Sildenafil Citrate
Properties: This product is a film-coated tablet, which is white to almost white after removing the coating.
Indications: Sildenafil is suitable for the treatment of erectile dysfunction.
Specification: 25mg*21 tablets/box
Usage and dosage: For most patients, the recommended dose is 50 mg, which can be taken as needed about 1 hour before sexual activity; however, it can be taken at any time within 0.5 to 4 hours before sexual activity. Based on the efficacy and tolerance, the dose can be increased to 100 mg (the maximum recommended dose) or reduced to 25 mg, taking up to once a day.
Adverse reactions: 1. In global clinical trials, more than 3,700 patients (aged 19 to 87 years) have taken sildenafil. More than 550 patients have been treated for more than one year. 2. In placebo-controlled clinical trials, the rate of discontinuation due to adverse events (2.5%) in the experimental group was not significantly different from that in the placebo group (2.3%). Adverse events are generally short-lived and mostly mild to moderate in nature. 3. In various forms of clinical trials, adverse events reported by patients in the experimental group are usually similar. In fixed-dose trials, the occurrence of certain adverse events increased with increasing dose. In general, flexible dose trials can better reflect the recommended dosage and usage of drugs, and the nature of the adverse events seen in the trial is similar to that of the fixed dose trial.
Contraindications: Patients taking any dosage form of nitrate ester drugs, whether it is taken regularly or intermittently, are contraindications. Patients who are allergic to any ingredient in sildenafil are contraindicated.
Note: The interaction of sildenafil-nitrates on blood pressure can last from the start of administration to the entire 6-hour observation period. Therefore, in any case, the combined administration of sildenafil and organic nitrates or the provision of NO drugs (such as sodium nitroprusside) are contraindicated. Sildenafil should be used with caution in the following patients: Anatomical malformations of the penis (such as penile deviation, cavernous fibrosis, Peyronie's disease), diseases that easily cause priapism (such as sickle cell anemia, multiple myeloma, leukemia) . The safety and effectiveness of other methods of treating erectile dysfunction in combination with this product have not been studied, and combined use is not recommended. When cardiovascular risk factors exist, there is a risk of non-fatal/fatal cardiac events in sexual activity after medication. If symptoms such as angina, dizziness, nausea, etc. occur at the beginning of sexual activity, sexual activity must be terminated. After the approval of this product abroad, there have been a small number of reports of prolonged erection time (more than 4 hours) and priapism (painful erections more than 6 hours). If the erection continues for more than 4 hours, the patient should seek medical attention immediately. If priapism is not treated immediately, penile tissues may be damaged and permanent erectile function may be lost. Sildenafil has no protective effect on sexually transmitted diseases.
Drug interactions: The effect of other drugs on sildenafil: In vitro experiments: The metabolism of this product is mainly through cytochrome P450 3A4 (main pathway) and 2C9 (secondary pathway), so inhibitors of these isoenzymes will reduce sildena Non-clear. In vivo experiment: Healthy volunteers took 50mg of this product and 800mg of cimetidine (a non-specific cytochrome P450 inhibitor) at the same time, resulting in a 56% increase in plasma sildenafil concentration. When a single dose of sildenafil 100mg is combined with erythromycin, a specific inhibitor of cytochrome P4503A4 (500mg twice a day for 5 days to reach steady state), the area under the drug-time curve (AUC) of sildenafil Increased by 182%; single-dose sildenafil 100mg combined with another CYP4503A4 inhibitor HIV protease inhibitor saquinavir, when reaching steady state (1200mg, three times a day), the latter's Cmax increased by 140%, AUC increased by 210 %, sildenafil does not affect the pharmacokinetics of the latter; more potent CYP4503A4 inhibitors such as ketoconazole and itraconazole may have greater effects; when combined with CYP4503A4 inhibitors (such as ketoconazole, When erythromycin and cimetidine are used in combination, the clearance rate of sildenafil decreases. It can be predicted that concurrent administration of CYP4503A4 inducers (such as rifampicin) will reduce plasma sildenafil levels. Single-dose antacids (aluminum hydroxide/magnesium hydroxide) have no effect on the bioavailability of this product; CYP4502C9 inhibitors (such as tolbutamide, warfarin), CYP4502D6 inhibitors (such as selective 5-hydroxytryptamine reuptake inhibition) Drugs, tricyclic antidepressants), thiazides and thiazide diuretics, angiotensin converting enzyme inhibitors, calcium channel blockers, etc., have no effect on the pharmacokinetics of sildenafil. Loop diuretics and potassium-sparing diuretics can increase the AUC of the active metabolite of sildenafil (N-desmethylsildenafil) by 62%, while non-selective-receptor blockers increase it by 102%. These effects on sildenafil metabolites will not cause clinical changes. The effect of sildenafil on other drugs: In vitro experiments: This product is a weak inhibitor of cytochrome P4501A2, 2C9, 2C19, 2D6, 2E1 and 3A4 (IC50>150μM). Since the peak plasma concentration of sildenafil after taking the recommended dose is about 1μM, sildenafil will not change the clearance of these isoenzyme substrates. In vivo test: In patients with hypertension, taking sildenafil (100mg) and amlodipine 5mg or 10mg at the same time, the systolic blood pressure in the supine position is further reduced by an average of 8mmHg, and the diastolic blood pressure is further reduced by an average of 7mmHg. No significant interaction between tolbutamide (250mg) and warfarin (40mg) metabolized by CYP4502C9 and sildenafil was found. Sildenafil (50mg) does not increase the bleeding time caused by aspirin (150mg). When the average maximum plasma alcohol concentration of healthy volunteers is 0.08%, sildenafil (50mg) does not enhance the antihypertensive effect of alcohol. Sildenafil (100mg) does not affect the steady-state pharmacokinetics of HIV protease inhibitors saquinavir and ritonavir, both of which are substrates of CYP4503A4.
Pharmacology and Toxicology: This product is an oral medicine for the treatment of erectile dysfunction (ED). It is the citrate of sildenafil, a selective inhibitor of phosphodiesterase type 5 (PDE5) specific to cyclic guanosine phosphate (cGMP). Mechanism of action: The physiological mechanism of penile erection involves the release of nitric oxide (NO) from the corpus cavernosum during sexual stimulation. NO activates guanylate cyclase and increases the level of cyclic guanosine phosphate (cGMP), which relaxes the smooth muscles in the cavernous body and fills the blood. Pharmacodynamics The effect of sildenafil on penile erectile response: Sildenafil citrate is a highly selective phosphodiesterase 5 (PDE5) inhibitor. PDE5 is highly expressed in the corpus cavernosum, but in other tissues (Including platelets, blood vessels and visceral smooth muscle, skeletal muscle), low expression. Sildenafil selectively inhibits PDE5, enhances the nitric oxide (NO)-cGMP pathway, and increases cGMP levels to cause relaxation of the smooth muscles of the corpus cavernosum, allowing patients with erectile dysfunction to have a natural erectile response to sexual stimulation. The erectile response generally increases with the increase of sildenafil dose and plasma concentration. Experiments show that the drug effect can last up to 4 hours, but the response is weaker than that at 2 hours. Sildenafil's response to myocardium: PDE5 does not exist in normal or diseased cardiac conduction tissues, cardiomyocytes, endothelial cells, and lymphoid tissues, so sildenafil (PDE5 inhibitor) has no positive inotropic effect and cannot Directly affect myocardial contractility. The effect of sildenafil on cardiac parameters: A single oral dose of sildenafil 100 mg in normal male volunteers did not have clinically significant changes in ECG. Eight patients with stable ischemic heart disease received intravenous injection of 40 mg of sildenafil in 4 doses under Swan-Ganz catheter monitoring. Results: The patient's systolic and diastolic blood pressures were lower than baseline They were down 7% and 10% respectively. The resting right atrium, pulmonary artery pressure, pulmonary artery wedge pressure, and cardiac output decreased on average by 28%, 28%, 20%, and 7%, respectively. Although this intravenous dose is 2 to 5 times higher than the average peak blood concentration of a single oral dose of 100 mg of sildenafil in healthy male volunteers, the above hemodynamic response still exists during exercise. Sildenafil's response to blood pressure: A single oral dose of sildenafil 100mg in healthy male patients resulted in a drop in supine blood pressure (average maximum amplitude of 8.4/5.5mmHg) 1-2 hours after taking the drug, the most obvious drop in blood pressure, 8 hours after taking the drug There is no difference with the placebo group. 25mg, 50mg, and 100mg sildenafil have similar effects on blood pressure and seem to have nothing to do with drug dosage and blood concentration. Patients taking nitrate ester drugs at the same time had a greater effect of lowering blood pressure. Hypotension (90/50mmHg) and nitrates or nitrate-providing drugs are strict contraindications to sildenafil. The greatest effect of sildenafil on blood pressure occurs approximately 1 hour after administration, which is consistent with the peak plasma peak of the drug. Therefore, at the peak plasma concentration of sildenafil, sexual activity may induce cardiac events. Although the hypotension caused by sildenafil is mild and short-lived (the blood pressure returns to baseline within 4 hours), the interaction between sildenafil and nitrates can produce significant and longer-term blood pressure reductions. Sildenafil has a short half-life, and the drug can be eluted within 24 hours (about 6 half-lives). The American College of Cardiology and the American Heart Association have clearly stated that sildenafil should not be used for those who have used nitrate drugs within 24 hours. The effect of sildenafil on vision: Studies have shown that this product has no effect on vision, electroretinogram, intraocular pressure and optic papilla size when taking 2 times the maximum recommended dose of the drug. There may be a transient blue/green color discrimination abnormality. Whether used alone or in combination with aspirin, this product has no effect on human bleeding time. In in vitro experiments, this product enhances the anti-human platelet aggregation effect of sodium nitroprusside (NO donor). In rabbits under anesthesia, the combined use of heparin and sildenafil has an additive effect on the prolongation of bleeding time, but similar human studies have not been conducted. After a single oral dose of 100 mg of sildenafil in healthy volunteers, sperm motility and morphology were not affected.
Pharmacokinetics: Sildenafil is quickly absorbed after oral administration, with an absolute bioavailability of about 40%. Its pharmacokinetic parameters are proportional to the dose within the recommended dose range. Elimination is dominated by liver metabolism (cytochrome P450 isoenzyme 3A4 pathway) to produce an active metabolite whose properties are similar to sildenafil, a potent inhibitor of cytochrome P450 isoenzyme 3A4 (CYP4503A4) ( Such as erythromycin, ketoconazole, itraconazole) and non-specific inhibitors of cytochrome P450 (CYP450) such as cimetidine combined with sildenafil may cause the plasma level of sildenafil to increase . The elimination half-life of sildenafil and its metabolites is about 4 hours. When 25-100mg is given on an empty stomach, the maximum plasma concentration (Cmax) is 127-560ng/ml in about 1 hour. Sildenafil or its major metabolite N-desmethyl metabolite (N-desmethyl) has a selectivity of about 50% for PDE5 and a protein binding rate of 96%. At the maximum plasma concentration of total sildenafil, the free sildenafil Cmax is 22ng/ml. After oral or intravenous administration, sildenafil is mainly excreted in the feces in the form of metabolites (about 80% of the oral dose), and a small part is excreted in the urine (about 13% of the oral dose).
Medication for pregnant women and breastfeeding women: Sildenafil is not suitable for women.
Child medication: Sildenafil is not suitable for newborns and children.
Medication for elderly patients: The clearance rate of sildenafil is reduced in healthy elderly volunteers (≥65 years old). High blood concentration may increase the occurrence of adverse events at the same time, so the starting dose is 25mg.
Overdose: When an overdose occurs, conventional supportive therapy should be taken as needed. Because of the high binding rate of sildenafil to plasma proteins, renal dialysis will not increase the clearance rate.
Storage: shading, sealed and stored.
Packing: 10 pieces per box
Validity period: 24 months
Approval number: National Medicine Standard H20173089
Company Name: Guangzhou Baiyunshan Pharmaceutical Co., Ltd. Guangzhou Baiyunshan Pharmaceutical General Factory