Viasan-LF, 50 mg 2 pcs

A product for the treatment of erectile dysfunction. It restores impaired erectile function and provides a natural response to sexual arousal.

Sildenafil is a potent and selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5), which is responsible for breakdown of cGMP in the cavernous body.

Sildenafil does not have a direct relaxing effect on the cavernous body, but actively enhances the relaxing effect of nitric oxide on this tissue. During sexual arousal local release of NO under the influence of sildenafil leads to inhibition of FDE5 and increase of cGMP level in the cavernous body, as a result of this there is relaxation of smooth muscles and increase of blood flow in the cavernous body.

Sildenafil may cause mild and transient color discrimination (blue/green).

The inhibition of FDE6, which is involved in the transmission of light in the retina, is thought to be the presumed mechanism of color vision impairment. In vitro studies have shown that the effect of sildenafil on FDE6 is 10 times inferior to its activity against FDE5.

In vitro studies show that the activity of sildenafil against FDEP5 is 10-10000 times greater than its activity against other phosphodiesterase isoforms (FDEP 1, 2, 3, 4 and 6). In particular, sildenafil activity against FDE5 is 4,000 times greater than its activity against FDE3 – cAMP-specific phosphodiesterase involved in heart contraction.

Pharmacokinetics

After oral administration sildenafil is rapidly absorbed. Absolute bioavailability is on average 40% (25-63%). After a single oral dose of 100 mg, Cmax is 18 ng/ml and is reached when taken on an empty stomach within 30-120 minutes. When sildenafil is taken in combination with fatty foods, the absorption rate is reduced; Tmax is increased by 60 min and Cmax is reduced by an average of 29%. The Vd of sildenafil in equilibrium is on average 105 L. Sildenafil and its main circulating N-desmethyl metabolite are approximately 96% bound to plasma proteins. Protein binding is independent of the total concentration of sildenafil. Less than 0.0002% of the dose (188 ng on average) was detected in semen 90 min after sildenafil administration.

Sildenafil is metabolized primarily by the microsomal liver isoenzymes CYP3A4 (main pathway) and CYP2C9.

The main circulating metabolite, which is formed by N-desmethylation of sildenafil, undergoes further metabolism. In terms of selectivity of action on FDE, the metabolite is comparable with sildenafil, and its activity against FDE5 in vitro is approximately 50% of the activity of sildenafil itself. Plasma concentration of the metabolite is about 40% of that of sildenafil. N-desmethylmetabolite undergoes further metabolism; its terminal T1/2 is about 4 hours.

The total clearance of sildenafil from the body is 41 l/h, and the T1/2 during the terminal phase is 3-5 hours. After oral administration sildenafil is excreted as metabolites mainly in the feces (about 80% of the dose) and, to a lesser extent, in the urine (about 13% of the dose).

In elderly patients (65 years and older) sildenafil clearance is decreased, and plasma concentrations of free active substance are about 40% higher than its concentration in young (18-45 years) patients.

In mild (KC 50-80 ml/min) and moderate (KC 30-49 ml/min) renal impairment, the pharmacokinetic parameters of sildenafil are unchanged after oral administration once (50 mg). In severe renal failure (CK≤30 ml/min), sildenafil clearance is decreased, resulting in approximately two-fold increase of AUC (100%) and Cmax(88%) compared to these parameters in normal renal function in patients of the same age group.

In patients with cirrhosis (Child-Pugh class A and B), sildenafil clearance is decreased, resulting in increased AUC (84%) and Cmax (47%) compared to those in normal liver function in patients in the same age group.

Indications

Active ingredient

Composition

How to take, the dosage

Viacil tablets are taken orally.

Application in adult patients

In most patients, the recommended dose is 50 mg administered 1 hour before sexual intercourse. Depending on the effectiveness and tolerability of the drug, the dose may be increased to the maximum recommended dose of 100 mg or reduced to 25 mg. The frequency of the maximum recommended dose is once a day.

The use in elderly patients

. In patients over 65 years of age with hepatic and severe renal impairment, as well as in concurrent use of potent cytochrome P450 3A4 inhibitors (ketoconazole, itraconazole, erythromycin, saquinavir), the initial dose of 25 mg is recommended because higher plasma concentrations may increase both the effectiveness and the frequency of adverse reactions.

Patient use in patients with renal impairment

In patients with mild to moderate renal impairment (creatinine clearance between 30 and 80 ml/min), no dose adjustment is necessary.

Due to decreased clearance of sildenafil in patients with severe renal impairment (creatinine clearance < 30 ml/min) a dose of 25 mg should be used.

Patient use in patients with impaired liver function

Because sildenafil clearance is reduced in patients with impaired liver function (e.g., cirrhosis), a dose of 25 mg is recommended.

Patient use in patients taking other drugs

In view of the evidence of sildenafil interaction with ritonavir, it is recommended that the maximum single dose of sildenafil 25 mg not be exceeded for 48 hours.

The use of sildenafil at a starting dose of 25 mg is recommended for patients concomitantly receiving CYP3A4 isoenzyme inhibitors (e.g., erythromycin, saquinavir, ketoconazole, itraconazole).

In order to minimize the likelihood of developing postural hypotension, patients should be in a stable condition when treated with alpha-adrenoblockers before starting sildenafil. In addition, it is recommended that sildenafil be started at lower doses in such cases.

Interaction

Concomitant use of CYP3A4 inhibitors (erythromycin, cimetidine) decreases sildenafil clearance and increases sildenafil plasma concentration.

Concomitant use of indinavir, saquinavir, ritonavir increases plasma Cmax and AUC of sildenafil due to inhibition of CYP3A4 isoenzyme by indinavir, saquinavir, ritonavir.

The stronger CYP3A4 isoenzyme inhibitors, such as ketoconazole or itraconazole, can be expected to increase plasma concentrations of sildenafil

Simultaneous use with nitrates increases the hypotensive effect of nitrates.

A case of development of rhabdomyolysis symptoms after a single dose of sildenafil in a patient receiving simvastatin has been described.

Special Instructions

In impaired renal function

In impaired renal function, the dose is 25 mg.

In impaired liver function

In impaired liver function the dose is 25 mg.

Periatric use

In elderly patients over the age of 65, the dose is 25 mg.

Periatric use.

Sildenafil is not used in patients under the age of 18 years.

Contraindications

Erectile dysfunction drugs, including sildenafil, should not be used in men for whom sexual activity is not recommended (e.g., patients with severe cardiovascular disease such as unstable angina or severe heart failure). Contraindicated in patients with vision loss in one eye due to anterior ischemic optical neuropathy.

The safety of sildenafil has not been studied in the following patient subgroups and therefore its use is contraindicated: severe hepatic failure, arterial hypotension (BP < 90/50 mm Hg), recent stroke or myocardial infarction, and inherited retinal degenerative diseases such as retinitis pigmentosa.

Hypersensitivity to any of the ingredients of the drug, therapy with nitrates.

Side effects

CNS disorders: headache, hot flashes, dizziness, insomnia are possible.

Digestive system disorders: dyspepsia, asthenia, diarrhea, abdominal pain, nausea are possible.

Muscular system disorders: arthralgia, myalgia, increased muscle tone.

Respiratory system disorders: nasal congestion, pharyngitis, rhinitis, sinusitis, respiratory tract infections, respiratory disorders.

A visual organ: changes in vision (mild and transient; mainly changes in the color of objects, as well as increased perception of light and impaired visual clarity), conjunctivitis.

Others: flu-like syndrome, development of infectious diseases, symptoms of vasodilation, back pain, rash, urinary tract infections, prostate disorders; in single cases, priapism.

Overdose

Symptoms: fever, dizziness, facial flushing, headache, blurred vision, dyspeptic phenomena, decreased blood pressure.

Treatment: symptomatic therapy; dialysis is ineffective.

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