Product Overview
[Drug name]
Generic name: Sildenafil citrate tablets
Trade name: Qianwei Sildenafil citrate tablets 50mg*7 tablets
Pinyin full code: QianWei ZuoZuoSuanXiDiNaFeiPian 5Omg*7Pian
[Main ingredients]
Sildenafil citrate.
[Properties]
Ganwei Sildenafil citrate tablets are blue diamond-shaped film-coated tablets, which appear white or off-white after removing the film coating.
[Indications/Main functions]
Suitable for the treatment of erectile dysfunction.
[Specification]
50mg*7 tablets
[Usage and Dosage]
1. For most patients, the recommended dose is 50mg, taken as needed about 1 hour before sexual activity; but it can be taken at any time within 0.5~4 hours before sexual activity. Based on efficacy and tolerability, the dose can be increased to 100mg (maximum recommended dose) or reduced to 25mg. Take up to 1 time a day. In the absence of sexual stimulation, the recommended dose of sildenafil has no effect. 2. The following factors are associated with increased plasma sildenafil levels (AUC): age over 65 years old (increase of 40%), liver damage (such as cirrhosis, increase of 80%), severe renal damage (creatinine clearance <30m/min, increase of 100%), and concurrent use of potent cytochrome P4503A4 inhibitors (ketoconazole, itraconazole (increase of 200%), erythromycin (increase of 182%), saquinavir (increase of 210%)). Since higher plasma levels may increase both drug efficacy and the incidence of adverse events, the starting dose for these patients is preferably 25 mg. 3. A study conducted in healthy subjects without HIV infection showed that Ritonavir significantly increased the blood level of sildenafil (AUC) by 11 times.
[Adverse Reactions]
The following are adverse events with an incidence of <2% in controlled clinical trials. It is not certain whether their occurrence is caused by sildenafil. Those events that may be related to medication are included here, but minor events and inaccurate reports are omitted. 1. Systemic reactions: facial edema, photosensitivity reaction, shock, fatigue, pain, chills, accidental falls, abdominal pain, allergic reaction, chest pain, accidental injury. 2. Cardiovascular system: angina, atrioventricular block, migraine, syncope, tachycardia, palpitations, hypotension, postural hypotension, myocardial ischemia, cerebral thrombosis, cardiac arrest, heart failure, abnormal electrocardiogram, cardiomyopathy. 3. Digestive system: vomiting, glossitis, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, abnormal liver function, rectal bleeding, gingivitis. 4. Blood and lymphatic system: anemia and leukopenia. 5. Metabolism and nutrition: thirst, edema, gout, unstable diabetes, hyperglycemia, peripheral edema, hyperuricemia, hypoglycemic reaction, hypernatremia. 6. Skeletal musculoskeletal system: arthritis, arthrosis, myalgia, tendon rupture, tenosynovitis, bone pain, myasthenia, synovitis. 7. Nervous system: ataxia, hypertonia, neuralgia, neuropathy, paresthesia, tremor, dizziness, depression, insomnia, drowsiness, abnormal dreams, weakened reflexes, and dysesthesia. 8. Respiratory system: asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, sputum, and cough. 9. Skin and its appendages: urticaria.
[Contraindications]
Currently, there is no clinical controlled trial data on the safety and efficacy of sildenafil in the following populations. Prescriptions should be used with caution in such patients: 1. Patients with myocardial infarction, shock, or life-threatening arrhythmias within the last 6 months. 2. Patients with resting hypotension (blood pressure below 90/50 mmHg) or hypertension (blood pressure above 170/110 mmHg). 3. Patients with heart failure or unstable angina due to coronary heart disease. 4. Patients with pigmentary retinitis (a small number of patients with this disease have hereditary abnormalities of retinal phosphodiesterase). 5. Patients with sickle cell anemia or related anemia.
[Drug Interactions]
The effects of other drugs on sildenafil: In vitro experiments: This product is metabolized mainly through cytochrome P4503A4 (main pathway) and 2C9 (minor pathway), so inhibitors of these isozymes will reduce the clearance of sildenafil. In vivo experiments: Healthy volunteers took 50 mg of this product and 800 mg of cimetidine (a nonspecific cytochrome P450 inhibitor) at the same time, resulting in a 56% increase in the plasma concentration of sildenafil.
When a single dose of sildenafil 100 mg was used in combination with erythromycin, a specific inhibitor of cytochrome P4503A4 (500 mg, twice a day, for 5 days to reach steady state), the area under the concentration-time curve (AUC) of sildenafil increased by 182%; when a single dose of sildenafil 100 mg was used in combination with another CYP4503A4 inhibitor, HIV protease inhibitor saquinavir, to reach steady state (1200 mg, three times a day), the Cmax of the latter increased by 140% and the AUC increased by 210%, and sildenafil did not affect the pharmacokinetics of the latter; the above effects may be greater for more potent CYP4503A4 inhibitors such as ketoconazole and itraconazole; when used in combination with CYP4503A4 inhibitors (such as ketoconazole, erythromycin, and cimetidine), the clearance rate of sildenafil was reduced.
[Precautions ]
The interaction between sildenafil and nitrates in affecting 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) is contraindicated. Qianwei Sildenafil Citrate Tablets should be used with caution in the following patients: patients with anatomical malformations of the penis (such as penile deviation, cavernous fibrosis, Peyronie's disease), diseases that are prone to abnormal penile erections (such as sickle cell anemia, multiple myeloma, leukemia). The safety and efficacy of other methods for the treatment of erectile dysfunction in combination with this product have not been studied, and combined use is not recommended. In the presence of cardiovascular risk factors, sexual activity after medication has the risk of non-fatal/fatal cardiac events. If symptoms such as angina pectoris, dizziness, and nausea occur at the beginning of sexual activity, sexual activity must be terminated. After approval for marketing abroad, there have been a small number of reports of prolonged erections (more than 4 hours) and abnormal erections (painful erections for more than 6 hours). If an erection lasts for more than 4 hours, the patient should see a doctor immediately.
If priapism is not treated immediately, penile tissue may be damaged and permanent erectile dysfunction may occur. Sildenafil does not protect against sexually transmitted diseases.
[Use in Elderly Patients]
The clearance of Qianwei Sildenafil Citrate Tablets in healthy elderly volunteers (≥65 years old) is reduced. Higher blood drug concentrations may also increase the occurrence of adverse events, so the starting dose is preferably 25 mg.
[Overdose]
When drug overdose occurs, routine supportive therapy should be taken as needed. Because sildenafil has a high binding rate to plasma proteins, renal dialysis will not increase the clearance rate.
