Viagra is the most popular medication used for the treatment of erectile dysfunction.
- The active substance: Sildenafil Citrate;
- Administration: The drug is used to improve erectile function and is used for erectile dysfunction treatment;
- Release Form: coated light blue, diamond-shaped, slightly convex pills with cut and round edges;
- Dosage: 25 mg , 50 mg, 100 mg;
- The composition is cellulose, magnesium stearate, calcium hydrogen phosphate anhydrous, croscarmellose sodium.
Dosage and Instructions for Use
Viagra is taken orally half an hour before sexual intercourse. Its daily recommended dose is 100 mg but it can be correspondingly reduced to 50 and 25 mg considering individual medication tolerance. The daily dose of 100 mg should be taken no more than once a day.
Mechanism of Action
Viagra is proven and most convenient drug for erectile dysfunction treatment. This medication is a selective inhibitor of specific phosphodiesterase cGMP 5 (PDE5).
The drug works with sexual stimulation presence only. The remedy does not contribute to visual loss syndrome and has no effect on intraocular pressure as well as on pupil size.
Sildenafil has no direct relaxing effect on isolated corpus cavernosum but enhances a relaxing effect of nitric oxide – NO on this tissue by inhibiting PDE5, which is responsible for cGMP degradation in the cavernous body.
PDE5 inhibition by sildenafil influence results in increased cGMP level in the cavernous body, resulting in smooth muscle relaxation and increased blood flow to the cavernous body.
In some patients, 1 hour after drug administration at a dose of 100 mg using Farnsworth-Munsell 100 showed mild and transient impaired ability to distinguish between color shades (blue/green); 2 hours after receiving these changes disappear.
It is believed that color vision violation is caused by PDE6 inhibition, which is involved in the transmission of light in the retina. Canadian Viagra has no effect on visual acuity, contrast perception, electroretinogram, intraocular pressure and pupil diameter.
Pharmacokinetics
Pharmacokinetics of the drug depends on the dose from 25 mg to 100 mg per day.
Absorption into Blood
Sildenafil is fairly rapidly absorbed. After receiving 100 mg of sildenafil limiting concentration of drug in the blood is 18 ng / ml (38nM), while taking the drug without food it is absorbed within half an hour to two hours min (1 hour on average).
At fatty foods use, the intake of sildenafil in blood is increased by about half an hour, and maximum concentration in blood is reduced by 29%
Distribution
Sildenafil and its major component in approximately 96% are bound to plasma proteins. Sildenafil concentration has no effect on protein binding. 105 liters – Vd sildenafil at steady state, indicating that its distribution into tissues.
When receiving 100 mg of sildenafil, a half hour after administration were detected 0.0002% (average 188 ng) in the sperm preparation.
Metabolism
- Basically, Sildenafil Citrate is metabolized under the influence of CYP3A4 (major route) and CYP2C9 (minor route) of hepatic microsomal isoenzymes.
- By productivity action on PDE metabolite is comparable with sildenafil and its activity against PDE5 in vitro is approximately 50% of sildenafil performance.
- The concentration of the metabolite in plasma is approximately 40% of that of sildenafil.
Breeding
The total clearance of sildenafil from the body is 41 l / h, T1 / 2 Baths. phase – 3-5 hours after oral or / in the introduction of Viagra comes in form of metabolites in feces of 80% of the dose in urine about 13% of the dose.
Indications
Erectile dysfunction is the inability to achieve or maintain an erection necessary for normal sexual intercourse.
Viagra works only if there is sexual stimulation. The drug is not intended for use in women, but there is a special drug Pink Female Viagra for women.
Dosage
- The drug is taken orally;
- The usual initial dose is 50 mg for 1 hour before intercourse. Given the lack of effect and side effects, the dosage can be increased to 100 mg or decreased to 25 mg;
- Take no more than 1 time per day. For elderly men dose adjustment is required;
- In severe renal insufficiency (creatinine clearance);
- In liver pathologies, the dosage can be reduced to 25 mg;
- When combined with ritonavir, the maximum single dose of sildenafil should be 25 mg, no more than 1 time in 48 hours;
- In a joint application with inhibitors of CYP3A4 isoenzyme (such as erythromycin, saquinavir, ketoconazole, itraconazole), the initial dose should be 25 mg;
- To minimize the risk of postural hypotension in patients taking alpha-blockers, Sildenafil should be taken only after hemodynamic stabilization which is achieved in these patients. Feasibility of reducing starting dose of sildenafil should be considered.
Side Effects
Side effects are usually mild or absent. The frequency of adverse events is increased with dose.
Common side effects:
- Nervous system: a headache (10.8%);
- Cardiovascular system: vasodilation (flushing) (10.9%).
Digestive System:
- dyspepsia (3.0%);
- hromatopsiya (mild and transient, mostly change perception of color shades)(1.1%);
- Cardiovascular palpitations (1.0%);
- Respiratory rhinitis (nasal congestion) (2.1%).
In case of an overdose, the likelihood of side effects is increased:
- Immune System: hypersensitivity reactions (including rash);
- Cardiovascular system: tachycardia, decreased blood pressure, fainting, nosebleeds;
- Digestive system: vomiting;
- Bodies: eye pain, eye redness / scleral injection;
- Reproductive system: prolonged erection and/or priapism.
Contraindications
The absolute contraindication for Viagra is hypersensitivity and components intolerance.
The drug is also contraindicated in men who take donator of nitric oxide, nitrates in any form as sildenafil enhances the hypotensive effect of nitrates.
You should not take this drug in the following diseases:
- anatomical penile deformity;
- cavernous fibrosis;
- angulation;
- Peyronie’s disease;
- drepanocytemia;
- multiple myeloma;
- leukosis;
- thrombocytopenia.
Other contraindications:
- diseases accompanied by bleeding;
- aggravation of gastric ulcer and duodenal ulcer;
- retinitis pigmentosa;
- heart failure;
- unstable angina;
- transferred in the last 6 months, myocardial infarction or blood stroke;
- severe arrhythmia;
- hypertension.
Information for Patients
Canadian Health and Care Mall recommends you to determine erectile dysfunction causes and determine correct treatment, it is necessary to consult a doctor.
Sexual contact is not recommended for men with:
- heart disease;
- unstable angina;
- myocardial infarction or stroke;
- arrhythmia;
- hypertension;
- hypotension.
Additional Information
The widely known remedy for impotence is fanned by the mass myths. Fiction is often difficult to be distinguished from the reality if you do not have information about this popular drugs.
The first thing to know about Viagra is that this drug is not an aphrodisiac. This drug does not increase sexual desire but only helps to improve erection during sexual stimulation. Funds from dull, unattractive partner yet, unfortunately, did not come up.
The medicine works by dilating blood vessels in the body, causing heart, lungs and other organs receive more blood. Moreover, Viagra relaxes spasms of smooth muscles in the penis. About 70% of men taking this drug reported about improved erection.