sildenafil | Viagra tablets 50 mg, 12 pcs.

Release form

Tablets

Packing

12 pcs.

Pharmacological action

Sildenafil is a potent selective inhibitor of cGMP-specific type 5 phosphodiesterase (PDE5).

The implementation of the physiological mechanism of erection is associated with the release of nitric oxide (NO) in the cavernous body during sexual stimulation. This, in turn, leads to an increase in cGMP level, subsequent relaxation of the smooth muscle tissue of the cavernous body and an increase in blood flow.

Sildenafil does not have a direct relaxing effect on an isolated cavernous body in humans, but enhances the effect of NO by inhibiting PDE5, which is responsible for the breakdown of cGMP.

Sildenafil is selective for PDE5 in vitro, its activity for PDE5 is superior to that of other known phosphodiesterase isoenzymes: PDE6 - 10 times PDE1 - more than 80 times PDE2, PDE4, PDE7-PDE11 - more than 700 times. Sildenafil is 4,000 times more selective for PDE5 compared to PDE3, which is crucial because PDE3 is one of the key enzymes for regulating myocardial contractility.

A prerequisite for the effectiveness of sildenafil is sexual stimulation.

Contraindications

Hypersensitivity to sildenafil or to any component of the

preparation use in patients receiving nitric oxide donors, organic nitrates or nitrates in any form continuously or intermittently, since sildenafil enhances the hypotensive effect of

nitrates with other drugs is not recommended for the treatment of erectile dysfunction (the safety and effectiveness of combination therapy has not been studied)

the drug is not intended for use in children and under stkov aged 18

medication is not for use in women.

Precautions: with anatomical deformation of the penis, with angulation, cavernous fibrosis, Peyronie’s disease, with diseases predisposing to the development of priapism, sickle cell anemia, multiple myeloma, leukemia, thrombocytopenia, with diseases accompanied by bleeding, with exacerbation of peptic ulcer of the stomach and duodenum, with hereditary retinitis pigmentosa, with heart failure, with unstable angina pectoris, with lasting 6 months myocardial infarction, with severe stroke, life-threatening arrhythmias, with arterial hypertension (blood pressure more than 170/100 mm Hg), with hypotension (blood pressure less than 90/50 mm Hg).

Special instructions

In order to diagnose erectile dysfunction, determine their possible causes and choose an adequate treatment, it is necessary to collect a complete medical history and conduct a thorough physical examination.

Sexual activity poses a certain risk for heart diseases in this regard, before starting any therapy for erectile dysfunction, the doctor may consider it necessary to examine the cardiovascular system. Sexual activity is undesirable in patients with heart failure, unstable angina pectoris, myocardial infarction or stroke, life-threatening arrhythmias, hypertension (BP> 170/100 mmHg) or hypotension (

BP) Drugs intended for treatment of erectile dysfunction should not be prescribed to men for whom sexual activity is undesirable.

Viagra has a systemic vasodilating effect, which leads to a transient decrease in blood pressure. This effect is not clinically significant and does not lead to any consequences in most patients. However, before prescribing the drug Viagra, the doctor must carefully weigh the risk of unwanted manifestations of vasodilating effects in patients with certain concomitant diseases, especially against the background of sexual activity. Increased susceptibility to vasodilators is observed in patients with left ventricular outflow tract obstruction (e.g., aortic stenosis, hypertrophic obstructive cardiomyopathy), as well as a rare syndrome of multiple systemic atrophy, which manifests itself as a severe violation of the regulation of blood pressure by the autonomic nervous system.

Influence on the ability to drive vehicles and control mechanisms

While taking Viagra, there was no negative effect on the ability to drive a car or other technical means. However, since when taking the drug, a decrease in blood pressure, the development of chromatopsy, blurred vision, it is necessary to carefully consider the individual effect of the drug in these situations, especially at the beginning of treatment and when changing the dosage regimen.

Composition

1 tablet contains:

Active ingredient: sildenafil (in the form of citrate) 50 mg.

Excipients: microcrystalline cellulose, calcium hydrogen phosphate, croscarmellose sodium, magnesium stearate.

Film composition: Opadry blue OY-LS-20921 (hypromellose, lactose, triacetin, titanium dioxide (E171), aluminum varnish based on indigo carmine (E132)) and Opadry transparent YS-2-19114-A (hypromellose, triacetin).

Dosage and administration of

The drug is taken orally.

For most patients, the recommended dose is 50 mg approximately 1 hour before sexual activity. Given the effectiveness and tolerability, the dose can be increased to 100 mg or reduced to 25 mg.

The maximum recommended dose is 100 mg. The maximum recommended frequency of use is 1 time / day.

In renal failure of mild to moderate severity

In renal failure of mild to moderate severity (CC 30-80 ml / min) dose adjustment is not required.

With severe renal failure (CC

With impaired liver function

With impaired liver function, the dose can be reduced to 25 mg.

When used together with ritonavir

When used together with ritonavir, the maximum single dose of Viagra should be 25 mg, the application rate is 1 time per 48 hours.

When used together with inhibitors of the isoenzyme CYP3A4

When used together with inhibitors of isoenzyme CYP4 saquinavir, ketoconazole, itraconazole) the initial dose of Viagra should be 25 mg.

In patients taking alpha-blockers

In order to minimize the risk of developing postural hypotension in patients taking alpha-blockers, sildenafil should only be started after hemodynamic stabilization is achieved in these patients. The feasibility of lowering the initial dose of Viagra should be considered.

Side effects

Side effects are usually transient and mild or moderate.

The incidence of adverse events increases with increasing dose.

Nervous system: dizziness - sildenafil (%) - 2.9, placebo (%) - 1.0. Most often (> 1/10) - headache - sildenafil (%) - 10.8, placebo (%) - 2.8.

Cardiovascular system: increased heart rate - sildenafil (%) - 1.0, placebo (%) - 0.2. Often (> 1/100 and <1/10) - vasodilation (flushing) - sildenafil (%) - 10.9, placebo (%) - 1.4.

Organ of vision: changes in vision (blurred vision, change in sensitivity to light) - sildenafil (%) - 2.5, placebo (%) - 0.4. Chromatopsia (mild and transient, mainly a change in the perception of color shades) - sildenafil (%) - 1.1, placebo (%) - 0.03.

Respiratory system: rhinitis (nasal congestion) - sildenafil (%) - 2.1, placebo (%) - 0.3.

Digestive system: dyspepsia - sildenafil (%) - 3.0, placebo (%) - 0.4.

When using the drug in doses exceeding the recommended side effects were similar to those noted above, but were usually more common.

Allergic reactions: hypersensitivity reactions (including skin rash).

From the side of the central nervous system: convulsions.

From the cardiovascular system: tachycardia, decreased blood pressure, fainting nosebleeds.

From the digestive system: vomiting.

From the side of the organ of vision: eye pain, redness of the eyes / injection of the sclera.

From the reproductive system: prolonged erection and / or priapism.

Drug interaction

The influence of other drugs on the metabolism of sildenafil

Sildenafil metabolism occurs mainly in the liver under the action of the isoenzymes CYP3A4 (the main pathway) and CYP2C9, therefore, the inhibitors of these isoenzymes can increase, clearance of sildenafil.

With the simultaneous use of CYP3A4 inhibitors (such as ketoconazole, erythromycin, cimetidine) decreased clearance of sildenafil.

Cimetidine (800 mg), which is a non-specific inhibitor of CYP3A4, when taken with sildenafil (50 mg) causes an increase in plasma concentration of sildenafil by 56%.

A single dose of 100 mg sildenafil simultaneously with erythromycin, a specific inhibitor of CYP3A4 (when taking erythromycin 2 times / day, 500 mg for 5 days), against the background of achieving a constant level of erythromycin in the blood, leads to an increase in AUC of sildenafil by 182%.

With the simultaneous use of sildenafil (once at a dose of 100 mg) and saquinavir, which is both an HIV protease inhibitor and an inhibitor of CYP3A4 (when taking saquinavir 3 times / day at a dose of 1200 mg), while achieving a constant level of saquinavir in the blood, C max sildenafil in the blood increased by 140%, and AUC increased by 210%. Sildenafil did not affect the pharmacokinetic parameters of saquinavir.

Stronger inhibitors of the CYP3A4 isoenzyme, such as ketoconazole or itraconazole, can cause more pronounced changes in the pharmacokinetics of sildenafil.

The simultaneous use of sildenafil (once at a dose of 100 mg) and ritonavir, which is an inhibitor of HIV protease and a strong inhibitor of isoenzymes of the cytochrome P450 system (when taking ritonavir 500 mg 2 times / day), while achieving a constant level of ritonavir in the blood, C max sildenafil increased by 300% (4 times), and AUC by 1000% (11 times). After 24 h, the concentration of sildenafil in the blood plasma was approximately 200 ng / ml (with a single use of one sildenafil - 5 ng / ml).

If sildenafil is taken in recommended doses by patients, receiving at the same time strong CYP3A4 inhibitors, then C max of free sildenafil does not exceed 200 nM, and the drug is well tolerated.

A single dose of antacid (magnesium hydroxide / aluminum hydroxide) does not affect the bioavailability of sildenafil.

CYP2C9 inhibitors (such as tolbutamide, warfarin), CYP2D6 (such as selective serotonin reuptake inhibitors, tricyclic antidepressants), thiazides and thiazide-like diuretics, ACE inhibitors and calcium antagonists do not affect the pharmacokinetic parameters.

Concomitant use of azithromycin (500 mg / day for 3 days) does not affect AUC, C max, T max, excretion rate constant, and T 1/2 of sildenafil or its main circulating metabolite.

Effect of sildenafil on other drugs

Sildenafil is a weak inhibitor of isoenzymes of the P450 cytochrome system - 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4 (IR 50> 150 μmol). It is unlikely that sildenafil can affect the clearance of substrates of these isoenzymes.

Sildenafil enhances the hypotensive effect of nitrates both with prolonged use and with acute indications. In this regard, the use of sildenafil in combination with nitrates or nitric oxide donors is contraindicated.

With the simultaneous administration of the alpha-blocker doxazosin (4 mg and 8 mg) and sildenafil (25 mg, 50 mg and 100 mg) in patients with benign prostatic hyperplasia with stable hemodynamics, the average additional decrease in systolic / diastolic blood pressure in the supine position was 7/7 mmHg, 9/5 mmHg and 8/4 mmHg respectively, and in a standing position - 6/6 mm Hg, 11/4 mm Hg and 4/5 mm Hg respectively. Rare cases of the development of symptomatic postural hypotension in such patients, manifested in the form of dizziness (without fainting), have been reported. In some sensitive patients receiving alpha-blockers, the simultaneous use of sildenafil can lead to symptomatic hypotension.

Signs of a significant interaction of sildenafil with tolbutamide (250 mg) or warfarin (40 mg), which are metabolized by CYP2C9, were not detected.

Sildenafil at a dose of 100 mg does not affect the pharmacokinetic parameters of HIV protease inhibitors at their constant concentration in the blood, such as saquinavir and ritonavir, which are simultaneously substrates of CYP3A4.

Sildenafil (50 mg) does not cause an additional increase in bleeding time when taking acetylsalicylic acid (150 mg).

Sildenafil (50 mg) does not enhance the hypotensive effect of ethanol in healthy volunteers with a maximum blood ethanol level of an average of 80 mg / dl.

In patients with hypertension, no signs of interaction of sildenafil (100 mg) with amlodipine were detected. The average additional decrease in blood pressure in the supine position is: systolic - by 8 mm Hg, diastolic - by 7 mm Hg.

The use of sildenafil in combination with antihypertensive agents does not lead to additional side effects.

Overdose of

Symptoms: with a single dose of the drug in a dose of up to 800 mg, adverse events were comparable to those of sildenafil at lower doses, but were more common.

Treatment: symptomatic therapy is given if necessary. Hemodialysis does not accelerate clearance of sildenafil, as the latter actively binds to plasma proteins and is not excreted in the urine.

Storage conditions

Store in a dry place at a temperature not exceeding 30 РC.

Expiration

5 years.

Active ingredient

Sildenafil

Prescription conditions from

pharmacies prescription

Dosage form

tablet