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Email: durante5 (nospam) i.ua
27 Dec 2009
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The drug, intended for the treatment of erectile
Trade name of drug: <strong>viagra</strong>
Dosage form: tablets of 50 mg to 100 mg.
Composition: active ingredient in <strong>viagra</strong> is sildenafil citrate, which is contained in the tablets in doses equivalent to 50 mg or 100 mg Sildenafil.
Excipients: microcrystalline cellulose, calcium hydrophosphate (anhydrous), croscarmellose sodium, magnesium stearate. hypromellose, titanium dioxide (E171), lactose, triatsetin, indigo carmine aluminum lacquer (E132).
<strong>viagra</strong> is an oral drug for the treatment of erectile dysfunction. He restores impaired erectile function and provides a natural response to sexual stimulation. The physiological mechanism of erection of the penis involves release of nitric oxide (N0) in the cavernous body during sexual stimulation.
Nitric oxide activates the enzyme guanilattsikpazu, which leads to increased levels of cyclic guanosine monophosphate (cGMP), relaxation of the corpus cavernosum smooth muscle and increase blood flow to the penis. Sildenafil - a powerful and selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5), which is responsible for the breakdown of cGMP in the cavernous body. <strong>viagra</strong> has a peripheral effect on erections. Sildenafil has no direct relaxing effect on corpus cavernosum, but also actively enhances the relaxing effect of N0 on this fabric. When activated, the way MO / cGMP, which persist in sexual arousal, inhibition of PDE5 under the influence of sildenafil increases the levels of cGMP in the cavernous body.
The volume of distribution (Vss) Sildenafil at steady state an average of 105l, which indicates that its distribution in tissues. Sildenafil and its major circulating metabolite M-desmetilovy approximately 96% bound to plasma proteins. Protein binding is not dependent on the total concentration of the drug <strong>viagra</strong>. In healthy volunteers receiving the drug <strong>viagra</strong> (single dose of 100 mg), less than 0.0002% (average 188 ng) dose was found in semen after 90 min after administration.
Sildenafil metabopiziruetsya primarily by CYP3A4 (major route) and CYP2C9 (optional path) of the liver microsomal isoenzymes. The main circulating metabolite is formed by the M-desmetilirovaniya Sildenafil. On the selectivity of action on PDE metabolite comparable with sildenafil, and its activity against PDE5 approximately 50% of the activity of the drug. Metabolite concentration in plasma is approximately 40% from those of sildenafil. M-desmetilmetabolit undergoes further metabolism, the final period of its half-life is about 4 hours.
The total clearance of sildenafil from the body is equal to 41 l / h, and the final half-period - 3-5 hours after oral or intravenous administration of sildenafil is excreted as metabolites primarily in the faeces (approximately 80% of the administered dose) and to a lesser extent in urine ( approximately 13% of the administered dose).
Pharmacokinetics in special groups of patients:
In healthy elderly volunteers (65 years and older) sildenafil clearance was reduced, and the concentration of free drug substance in the plasma by approximately 40% higher than its level in healthy young volunteers (18-45 years). However, analysis of safety data showed that age does not influence the frequency of adverse events.
In volunteers with mild (creatinine clearance 50-80 ml / min) and moderate (creatinine clearance 30-49 ml / min) renal insufficiency <strong>viagra</strong> pharmacokinetics after a single oral administration (50 mg) did not change. In volunteers with severe (creatinine clearance 30 ml / min) renal clearance of sildenafil decreased, which led to an increase in AUC (100%) and Cmax (88%) compared with those of volunteers, matched for age who did not suffer loss of kidney function .
In volunteers with hepatic cirrhosis (Child-Pugh A and B) sildenafil clearance is decreased, resulting in increased rates AUC (84%) and Cmax (47%) compared with those of volunteers of the same age not suffering from liver failure.
<strong>viagra</strong> is used to treat erectile dysfunction. In order for the drug <strong>viagra</strong> was launched to sexual arousal.
<strong>viagra</strong> is contraindicated in patients with hypersensitivity to any component tablets. With a definite influence on the exchange of nitric oxide / cGMP (see Pharmacodynamic properties), the drug <strong>viagra</strong> increased the hypotensive effect of nitrates, so it is contraindicated in patients receiving nitric oxide donator or nitrates in any form.
Safety of Sildenafil in the following subgroups of patients has not been studied, and therefore its use is contraindicated in them to get further information: a difficult hepatic failure, hypotension (blood pressure <90/50 mmHg. Cent.) Recent stroke or myocardial infarction and hereditary retinal degenerative diseases, such as pigmentation of the retina (a small number of these patients have genetic disorders, retinal phosphodiesterase).
Application of pregnancy and lactation:
<strong>viagra</strong> is not designed for use in women. Reproduction studies in rats and rabbits, oral use of sildenafil did not exert teratogenic effects, had no effect on reproductive function and did not cause any violation of the peri / postnatal development of the fetus and newborn. Single dose <strong>viagra</strong> orally at a dose of 100 mg in healthy volunteers was not accompanied by changes in sperm motility or morphology.
Dosage and method of application:
<strong>viagra</strong> tablets are inside.
Recommended dose of 50 mg taken only when needed about one hour before planned sexual activity. Given the efficacy and tolerability the dose may be increased to 100 mg or decreased to 25 mg. The maximum recommended dose is 100 mg. The maximum recommended frequency of application - once a day.
Application of the elderly and patients with impaired renal function or liver
In elderly people and patients with impaired renal function or liver recommended scheme of the same.
<strong>viagra</strong> should not be given to children.
In clinical studies, which were held in various countries around the world, the drug <strong>viagra</strong> used more than 3700 patients (aged 19 to 87 pet). Over 550 patients received liver for more than one year. Tolerability of the drug <strong>viagra</strong> has been good. In placebo controlled clinical studies, the frequency of discontinuation due to adverse events was low and comparable with that for placebo. Adverse events were generally transient and light to moderate. In studies with any design nature adverse events in patients receiving the drug <strong>viagra</strong>, has been similar. In studies with fixed doses of the frequency of adverse events increased with increasing dose. In studies with the selection of doses were selected (such studies to better reflect the recommended scheme of application), the nature of adverse events was comparable to that in studies with fixed doses.
In clinical studies, with an individual selection of doses, most often met the following adverse events whose relationship with the drug taking was possible, probable or unknown:
• Cardiovascular - headache, flushing, dizziness;
• Digestion - indigestion;
• breathing - nasal congestion;
• senses - vision changes (mild and transient, mostly change the color of objects, as well as increased perception of light and a violation of clarity of vision).
When using the drug <strong>viagra</strong> in doses greater than recommended, adverse events were similar to the above, but usually more often.
Cases of priapism have not been recorded.
In studies in healthy volunteers in single dose of the drug <strong>viagra</strong> in doses of 800 mg of adverse events were comparable with those in the admission of the drug <strong>viagra</strong> in lower doses, but occurred more frequently. In case of overdose should adopt standard symptomatic measures. Dialysis should not accelerate the clearance of sildenafil, as the latter is actively bound to plasma proteins and excreted in the urine.
Special warnings and special precautions:
For the diagnosis of erectile dysfunction, determine possible causes of their choice and adequate treatment is necessary to collect a complete medical history and thorough physical examination. Sexual activity is a risk in the presence of heart disease. In this connection, before any therapy at the violations of erection doctor may deem it necessary to study the cardiovascular system.
Preparations intended for the treatment of erectile dysfunction, should be used with caution in patients with anatomical deformation of the penis (eg, angulation, cavernous fibrosis or Peyronie's disease) and persons suffering from diseases that predispose to the development of priapism (such as sickle cell anemia, multiple myeloma, or leukemia).
Preparations intended for the treatment of erectile dysfunction, should not be given to men for whom sexual activity is undesirable. Safety and effectiveness of the drug <strong>viagra</strong> in combination with other tools designed for the treatment of erectile dysfunction, were not studied. In this regard, the use of such combinations is not recommended.
<strong>viagra</strong> does not affect bleeding time, including the appointment in combination with aspirin. Studies of human platelets in vitro suggest that sildenafil enhances antiagregatsionny effect of sodium nitroprusside (nitric oxide donator). No information about the safety of the drug <strong>viagra</strong> in patients with diseases which are accompanied by bleeding, or exacerbation of peptic ulcer not. Therefore such patients the drug <strong>viagra</strong> should be used with caution.
A small number of patients with hereditary retinitis pigmentosa are inherited disorders the activity of phosphodiesterases in the retina. No information about the safety of the drug <strong>viagra</strong> in patients with retinitis pigmentosa no. Therefore such patients the drug <strong>viagra</strong> should be used with caution.
Effects on ability to drive and use the technique:
When driving a car or machinery, special precautions are required.
Influence of other drugs on the drug <strong>viagra</strong>
Studies in vitro:
Metabolism Sildenafil is mainly influenced by isoforms ZA4 (main road) and 2S9 (less than a meaningful way) cytochrome P450. Consequently, inhibitors of these isoenzymes may reduce sildenafil clearance.
Studies in vivo:
Cimetidine (800 mg), a nonspecific inhibitor of CYP3A4, while admission to the drug <strong>viagra</strong> caused an increase in sildenafil plasma concentrations by 56% in healthy volunteers. Population pharmacokinetic analysis of the results of clinical trials have demonstrated reduction in sildenafil clearance with simultaneous application of inhibitors of CYP3A4 (such as ketoconazole, erythromycin, cimetidine). However, the frequency of adverse events in these patients is not increased.
Single reception antacid (magnesium hydroxide / aluminum hydroxide) did not affect the bioavailability of the drug <strong>viagra</strong>. According to population-based pharmacokinetic analysis, the inhibitors of CYP2C9 (such as tolbutamide, warfarin), CYP2D6 (such as selective serotonin reuptake inhibitors, antidepressants tritsikpicheskie), thiazides and tiazidopodobnye diuretics, loop and potassium-sparing diuretics, ACE inhibitors, calcium antagonists, beta-blockers and inducers metabolic CYP450 (such as rifampicin, barbiturates) no effect on the pharmacokinetics of sildenafil.
Effect of <strong>viagra</strong> on other drugs
Studies in vitro:
Sildenafil is a weak inhibitor of cytochrome P450 isoenzymes - 1A2, 2C9, 2C19, 206, 2E1 and ZA4 (IR, d> 150 mmol). In the application Sildenafil at recommended doses, the maximum concentration in plasma is about 1 mol, so it is unlikely that the drug <strong>viagra</strong> can affect the clearance of substrates of these isoenzymes.
Studies in vivo:
No evidence of significant interaction with tolbutamide (250 mg) or warfarin (40 mg), which are metabolized by CYP2C9, is not revealed. <strong>viagra</strong> (50 mg) caused no additional increase in bleeding while taking aspirin (150 mg). <strong>viagra</strong> (50 mg) did not increased the hypotensive effect of alcohol in healthy volunteers at the maximum level of alcohol in the blood in an average of 80 mg / dp. In patients with arterial hypertension drug interaction signs of <strong>viagra</strong> (100 mg) and amlodipine have been identified. The average additional reduction in blood pressure in the prone position (systolic - 8 mm Hg. Art., Diastolic - by 7 mmHg. Cent.) Was comparable to that at the reception of one drug <strong>viagra</strong> in healthy volunteers (see Pharmacodynamic properties). Analysis of information security has demonstrated no differences in the nature of side effects in patients receiving the drug <strong>viagra</strong> in combination with antihypertensive drugs and without them. <strong>viagra</strong> increased the hypotensive effects of nitrates in the acute sample and with prolonged use of the latter. In this regard, the use of the drug <strong>viagra</strong> in combination with nitrates or nitric oxide donators contraindicated (see Contraindications).
Shelf Life <strong>viagra</strong>: 2 years. <strong>viagra</strong> does not apply after the expiry date.
Storage <strong>viagra</strong>: Store at temperatures below 30 ° C. Before using the product, check the expiry date printed on the packaging. Keep out of reach of children.
Conditions of supply of the drug <strong>viagra</strong> Pharmacy: <strong>viagra</strong> dispensed by prescription.
This work is in the public domain