Sildenafil (Viagra)

 

S

ildenafil is most effective in men with mild to moderate ED. It is to be taken on an empty stomach approximately 1 hour before sexual activity. Sexual stimulation is necessary to activate response. Sildenafil is available as 25-, 50-, and 100-mg tablets. The maximum recommended use is once daily.

No evidence suggests that patients commonly develop either physical dependence on or tolerance to sildenafil. Patients who demonstrate dependence on sildenafil to achieve erection typically have psychological dependence. Sildenafil does not have the libido-stimulating activity typical of an aphrodisiac agent. In patients with penis deformation (eg, Peyronie disease), sildenafil should be used with caution. Its use should also be closely monitored in patients with conditions that predispose them to priapism, including multiple myeloma and sickle cell anemia.

Sildenafil should also be not administered or used with caution in patients with a history of various cardiovascular conditions, including the following:

Contraindications Angina Arrhythmia Coronary artery disease Heart failure Hyperlipidaemia Hypotension or hypertension Myocardial infarction Stroke

Other conditions of concern Bleeding disorders Diabetes Eye disorders (e.g., retinitis pigmentosa, nonarthritic anterior ischemic optic neuropathy) Kidney disease Leukaemia Liver disease Pulmonary veno-occlusive disease Stomach ulcer

Sildenafil use is contraindicated in patients taking the following medications:

Atazanavir Cobicistat Elvitegravir-cobicistat-emtricitabine-tenofovir disoproxil fumarate Isosorbide dinitrate

Isosorbide mononitrate Nelfinavir Nitroglycerin Riociguat Vericiguat

 

Riociguat is a guanylate cyclase stimulator used to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Coadministration of PDE-5 inhibitors (eg, avanafil, sildenafil, tadalafil, vardenafil) and guanylate cyclase stimulators is contraindicated owing to risk for additive hypotension. They should not be administered within 24 hours of each other.

 

ADVERSE EFFECTS: -

According to the US Food and Drug Administration, the most common adverse effects associated with sildenafil include the following:

Flushing & Headache Dyspepsia Abnormal vision Nasal congestion Back pain Dizziness/nausea

Myalgia Rash Epistaxis Insomnia Erythema Diarrhoea

 

TOXICITY: -

Sildenafil is recognized as having low general toxicity with no reproductive toxicity, genotoxicity, or carcinogenic properties. Single doses of as much as 800 mg have been found to result in an increased frequency and severity of adverse effects associated with lower doses. Dialysis does not help clear sildenafil because the drug is highly bound to plasma proteins and is not renally excreted. No antidotes are available for sildenafil.

 

Clinical studies of higher-than-recommended sildenafil doses showed dose-related increases in the frequency of visual adverse events; however, no clear relationship between dose and maximum blood pressure decreases or clinically significant changes on electrocardiography have been established. Patients who take sildenafil more often than once daily have an increased frequency of transient muscle ache without evidence of muscle damage.