-
Sildenafil mechanism of action
A potent and selective inhibitor of phosphodiesterase type 5 (PDE5) specific for cyclic guanosine monophosphate (cGMP) in the corpora cavernosa, where PDE5 is responsible for the degradation of cGMP.
-
Therapeutic indications sildenafil
Orally.
Erectile dysfunction. Treatment of pulmonary arterial hypertension typified as WHO functional class II and III (efficacy has been demonstrated in pulmonary hypertension 1 aria and pulmonary hypertension associated with connective tissue disease). Treatment of children aged 1 to 17 years with pulmonary arterial hypertension (efficacy has been demonstrated in terms of improving exercise capacity or pulmonary hemodynamics in 1st pulmonary hypertension and pulmonary hypertension associated with congenital heart disease).
IV route: treatment of adult patients (≥ 18 years) with pulmonary arterial hypertension who are temporarily unable to receive oral therapy, but who are clinically and hemodynamically stable.
-
Sildenafil dosage
oral. ads. and elderly:
– Erectile dysfunction:
Solid forms: initial 50 mg taken as needed/1 h before sexual activity, without food. Based on efficacy and tolerance, increase to 100 mg or decrease to 25 mg; max. 100 mg/1 time a day. Sexual stimulation is required.
Severe IR or IH: 25 mg, depending on efficacy and tolerance, can be increased to 50 mg and 100 mg.
Liquid forms: 2 ml (4 puffs), equivalent to 50 mg of sildenafil taken as needed, approximately one hour before sexual activity. Based on efficacy and tolerability, the dose may be increased to 4 ml (8 puffs), equivalent to 100 mg, or decreased to 1 ml (2 puffs), equivalent to 25 mg sildenafil. The maximum recommended dose is 4 ml (8 actuations), equivalent to 100 mg of sildenafil. The maximum recommended dosage schedule is once daily.
Severe IR (Clcr<30 mL/min): A dose of 25 mg (two sprays) should be considered for these patients. Based on efficacy and tolerability, the dose may be gradually increased to 50 mg.
– Treatment of pulmonary arterial hypertension as functional class II and III of the WHO: 20 mg/3 times a day at intervals of 6-8 hours, with or without food.
Severe IR or IH or concomitance with CYP3A4 inhibitors (erythromycin or saquinavir): 20 mg/2 times a day, after evaluating risk/benefit. In case of CYP3A4 inhibitors (clarithromycin, telithromycin and nefazodone): 20 mg/once a day.
Oral. Children from 1 to 17 years:
– Pulmonary arterial hypertension: patients ≤ 20 kg: 10 mg (1 ml of prepared suspension)/3 times a day, patients >20 kg: 20 mg (2 ml of prepared suspension or 1 tablet) /3 times a day. Do not use higher doses than recommended.
IV. Ads.:
– Tto. of pulmonary arterial hypertension: 10 mg (12.5 ml)/3 times a day in inj. IV bolus.
Severe IR or IH or concomitance with CYP3A4 inhibitors (erythromycin or saquinavir): 10 mg/2 times a day, after evaluating risk/benefit. In case of CYP3A4 inhibitors (clarithromycin, telithromycin and nefazodone): 10 mg/once a day.
-
Sildenafil mode of administration
N/A
-
Contraindications sildenafil
hypersensitivity to sildenafil; concomitant use with nitrates or nitric oxide donors; severe cardiovascular dysfunction, unstable angina or heart failure. severe cardiac; severe HI; hypotension; recent history of stroke or AMI; retinitis pigmentosa; combination with strong CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir); patients presenting with vision loss due to non-arteritic anterior ischemic optic neuropathy regardless of whether or not this episode was associated with prior exposure to a PDE5 inhibitor. Co-administration of PDE5 inhibitors, including sildenafil, with guanylate cyclase stimulators, such as riociguat, is contraindicated as it can potentially produce symptomatic hypotension.
-
Warnings and precautions sildenafil
severe RI; Mild HI; anatomical deformities of the penis (angulation, cavernous fibrosis or Peyronie’s disease) or with a predisposition to priapism (sickle cell anemia, multiple myeloma or leukemia), cases of prolonged erection and priapism have been reported with sildenafil during post-marketing experience. If the erection persists for more than 4 hours, the patient should immediately seek medical attention. If priapism is not treated immediately, penile tissue damage and permanent loss of potency can occur. Bleeding disorders or with active peptic ulcer. Consider cardiovascular status, due to cardiac risk associated with sexual activity. Not recommended in combination with alpha-blockers, or with other treatments. for erectile dysfunction. Discontinue if sudden visual disturbance occurs. Not recommended in children and < 18 years. In pulmonary arterial hypertension there may be > risk of hemorrhage in patients with tto. of antagonist of vit. K and in case of interrupting the tto. Gradual dose reduction is recommended. Caution concomitance with other tto. for pulmonary arterial hypertension (bosentan, iloprost); It should not be used in patients with pulmonary arterial hypertension secondary to sickle cell anemia. The efficacy of sildenafil in patients already on bosentan treatment has not been conclusively demonstrated. The safety and efficacy of sildenafil in patients with PAH when co-administered with other PDE5 inhibitor drugs have not been studied, and therefore its concomitant use is not recommended IV route: not recommended in hemodynamically unstable patients;
-
Sildenaffil liver failure
Contraindicated in severe IH. Caution in mild IH in erectile dysfunction: reduce initial dose to 25 mg; based on tolerance, increase dose to 50 mg and 100 mg. Caution in IH in pulmonary arterial hypertension: no dose adjustment is required, only if it is not well tolerated, adjust dose (oral): 20 mg/2 times a day, and dose (IV): 10 mg/2 times a day, after assess risk/benefit.
-
Renal insufficiency sildenaffil
Caution in severe IR in erectile dysfunction: solid forms: initial dose of 25 mg; based on tolerance, increase dose to 50 mg and 100 mg. Liquid forms: A dose of 25 mg (two sprays) should be considered for these patients. Based on efficacy and tolerability, the dose may be gradually increased to 50 mg. Caution in severe RF in pulmonary arterial hypertension: initial dose (oral): 20 mg/2 times a day, after evaluating risk/benefit; initial dose (IV): 10 mg/2 times a day, after evaluating risk/benefit.
-
Sildenafil interactions
Inhibited effect with: strong CYP3A4 inducers, such as carbamazepine, phenytoin, phenobarbital, St. John’s wort and rifampin.
Action and toxicity potentiated with: with CYP3A4 inhibitors (such as ketoconazole, erythromycin, cimetidine, grapefruit juice).
Toxicity potentiated by: HIV protease inhibitors-
Potentiates hypotensive effects of: nitrates, riociguat. Therefore, their concomitant administration is contraindicated.
Potentiation of toxicity with: alpha-blockers.
Co-administration of PDE5 inhibitors, including sildenafil, with guanylate cyclase stimulators, such as riociguat, is contraindicated as it can potentially produce symptomatic hypotension.
The safety and efficacy of combining sildenafil with other PDE5 inhibitors, other sildenafil-containing treatments for pulmonary arterial hypertension (PAH), or other treatments for erectile dysfunction have not been studied. Therefore, the use of such associations is not recommended.
-
Pregnancy sildenafil
There are no data on the use of sildenafil in pregnant women. Animal studies do not indicate direct or indirect harmful effects with respect to pregnancy and embryonic/foetal development. Animal studies have revealed toxicity with respect to postnatal development. Due to lack of data, sildenafil should not be used in pregnant women unless strictly necessary.
-
Sildenafil lactation
There are no adequate or well-controlled studies in lactating women. Data from a lactating woman indicate that sildenafil and its active metabolite N-desmethyl sildenafil are excreted in breast milk at very low levels. Clinical data on adverse effects in infants are not available, but the amounts ingested are not expected to cause adverse effects. The physician should carefully assess the mother’s clinical need for sildenafil and any possible adverse effects on the nursing infant.
-
Adverse reactions sildenafil
cellulitis, flu, bronchitis, rhinitis, gastroenteritis, sinusitis; anemia; fluid retention; insomnia, anxiety; headache, migraine, tremor, paresthesia, burning sensation, hypoesthesia; retinal hemorrhage, eye disorders, blurred vision, photophobia, chromatopsia, cyanopsia, eye irritation, eye hyperemia; Vertigo; flushing; bronchitis, epistaxis, cough, nasal congestion; diarrhea, dyspepsia; gastritis, disease for gastroesophageal reflux, hemorrhoids, abdominal distension, dry mouth; alopecia, erythema, night sweats; extremity pain, myalgia, back pain; pyrexia.
-
Effects on the ability to drive sildenafil
Dizziness and visual disturbances have been reported in clinical trials with sildenafil, therefore patients should be aware of how it may affect them before driving or operating machinery.