Things you should know about sildenafil



It is used to treat penis Erectile dysfunction (ED).


1. People who are allergic to Sildenafil.

2. Those who are using Nitroglycerin, Sodium nitroprusside or other organic nitrates.

Usage and dosage

For most patients, the recommended dose is 50mg, taken as needed approximately 1 hour before sexual activity, and sexual stimulation is required after taking the medication. However, it can be taken at any time within 0.5-4h before sexual activity. Based on efficacy and tolerance, the daily dose can be adjusted between 25-100mg, and the medication should not exceed once a day. (1) The recommended initial dose for patients with severe renal insufficiency (AUC and cmax almost double when creatinine clearance rate is less than or equal to 30ml/min) is 25mg. (2) The recommended initial dose for patients with liver dysfunction (such as cirrhosis, where AUC and cmax increase by 84% and 47% respectively) is 25mg.

2. The recommended starting dose for elderly people aged 65 and above is 25mg.

3. Dose for other diseases (1) The initial dose of 25 mg is appropriate for those who take powerful cytochrome P4503A4 inhibitor and Erythromycin at the same time. (2) It is recommended that Sildenafil should not be used more than 25mg every 48h for patients taking HIV protease inhibitor (such as Ritonavir).

Adverse reactions

1. Cardiovascular system: There are reports of adverse cardiovascular events such as myocardial infarction, cardiac Death during consensual sex, heart failure, arrhythmia, Hypotension, cerebral hemorrhage, cerebral thrombosis, transient local ischemic shock and hypertension, most of which occur during sexual activity or just after the end of the bundle, some occur within hours to days after medication or sexual activity, and even a few occur when sexual activity has not been carried out soon after medication. At present, it has not been determined whether these reactions are directly caused by Sildenafil or by multiple factors such as sexual activity and cardiovascular status of patients.

2. Digestive system: Dyspepsia (7%) and diarrhea (3%) may occur; There are reports of dry mouth, vomiting, dysphagia, glossitis, gingivitis, Stomatitis, Esophagitis, gastritis, colitis, liver dysfunction, rectal bleeding, etc.

3. Blood: Case reports of anemia and leukopenia.

4. Metabolism/Endocrine system: gout, diabetes, peripheral edema, Hyperuricemia, hypoglycemia, Hypernatremia, etc.

5. Respiratory system: nasal congestion may occur (4%); There are cases of asthma, pharyngitis, Sinusitis, bronchitis, phlegm, cough, dyspnea, etc.

6. Genitourinary system: urinary tract infection may occur (3%); There are reports of Cystitis, nocturia, frequent urination, Urinary incontinence, abnormal ejaculation, genital edema, lack of Orgasm, etc; There have also been reports of cases of prolonged penile erection time (over 4 hours), abnormal erection (painful erection over 6 hours), and hematuria.

7. Central nervous system: Headache (16%) and dizziness (2%) may occur; Ataxia, hypertonia, tremor, Neuralgia, neuropathy, paresthesia, dizziness, depression, anxiety, insomnia, lethargy, dreaminess, delayed reflexes, insensitivity, Seizure and other cases were reported.

8. Musculoskeletal system: there are joint diseases, Myalgia, tendon rupture, Tenosynovitis, bone pain, muscle weakness, Synovitis and other case reports.

9. Skin: Facial flushing (10%), skin rash (2%), Hives, herpes simplex, pruritus, skin ulcer, Contact dermatitis, exfoliative dermatitis and other cases were reported.

10. Eyes: there are reports of pupil enlargement, Conjunctivitis, eye bleeding, cataract, dry eye, eye pain, photophobia, red eye or eye congestion, eye burning, eye swelling and compression, increased intraocular pressure, retinal angiopathy or hemorrhage, vitreous detachment, perimacular edema, etc. Mild transient visual abnormalities (3%) can also occur, mainly manifested as light color, enhanced light perception, blurred vision, diplopia, transient visual loss, or decreased vision.

11. Ears: There have been reports of tinnitus and deafness.

12. Other: Systemic reactions may also occur, such as shock, fatigue, pain (such as chest pain), chills, allergic reactions, etc. [3]

Aftereffect reaction

The most common symptoms are headache, facial flushing, indigestion, and muscle pain, followed by nasal congestion, diarrhea, dizziness, and rash. Occasional transient visual abnormalities are seen, usually due to impaired color discrimination or increased sensitivity to light, with an incidence rate of 100mg dose often higher than 50mg dose. The aftereffects of Sildenafil include serious cardiac events (including myocardial infarction, sudden heart disease death, ventricular arrhythmia, cerebral vascular hemorrhage, transient ischemic attack, hypertension), seizures, anxiety, abnormal erections (pain, erections lasting for more than 6 hours), hematuria, diplopia, transient visual loss, decreased vision, eye bleeding, eye burning, eye swelling, increased intraocular pressure, retinal vascular disease or hemorrhage Vitreous detachment/traction and spotted edema.

matters needing attention

1. Use cautiously (1) Patients with retinitis pigmentosa or other retinal abnormalities (because a few patients may have genetic abnormalities of retinal Phosphodiesterase). (2) Patients who have experienced myocardial infarction, stroke, shock, or fatal arrhythmia within the past 6 months. (3) Patients with Hypotension or hypertension, heart failure, ischemic heart disease. (4) Patients with hemorrhagic diseases or active peptic ulcers. (5) Patients with diseases that can cause Priapism (such as sickle cell anemia, Multiple myeloma, leukemia). (6) Anatomically deformed penis (such as bending penis, fibrous degeneration or induration of Corpus cavernosum penis).

2. The effect of drugs on children Sildenafil is not applicable to children (especially newborns).

3. Studies on the impact of drugs on the elderly show that the clearance rate of Sildenafil in healthy elderly volunteers (not less than 65 years old) decreases, and the area under the curve increases by 40%. Since higher blood concentration may increase adverse reactions, the initial dose of Sildenafil should be reduced.

4. The pregnancy safety of Sildenafil is classified as Grade B by the US Food and Drug Administration (FDA).

5. It is not clear whether Sildenafil is secreted with milk.

6. Sildenafil is not applicable to women.

7. When Sildenafil is given to treat ED, its related causes should be treated. In addition, the recommended dose of Sildenafil did not work in the absence of sexual stimulation.

8. The transient reduction of supine blood pressure caused by Sildenafil is usually negligible for most patients, but it is still necessary to carefully consider whether this Vasodilation effect will bring adverse consequences to patients with Hypotension or other cardiovascular diseases, especially during sexual activity (when cardiovascular risk factors exist, sexual activity has potential risks to the heart). Therefore, Sildenafil should not be used to treat Erectile dysfunction in patients with cardiovascular disease.

9. If symptoms such as angina, dizziness, and nausea occur at the beginning of sexual activity, sexual activity must be terminated.

10. If the penis continues to erect for more than 4 hours after medication, corresponding treatment should be given; If an abnormal erection is not handled in a timely manner, the penile tissue may be damaged and lead to permanent loss of erectile function.

11. The safety and effectiveness of other methods for the treatment of Erectile dysfunction in combination with Sildenafil have yet to be studied, so the combination is not recommended.

12. It is unclear when patients can safely take nitrates after taking Sildenafil.

13. Studies have shown that when a single dose of 800mg is added to healthy volunteers, the adverse reactions are similar to those at low doses, but the incidence increases. When overdosing, routine supportive therapy should be taken as needed. Since Sildenafil has a high binding rate with Plasma protein binding and is not cleared from urine, hemodialysis will not increase the clearance rate.

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Post time: Jul-07-2023