Description and Composition of Si-Vega-Si
Si-Vega-Si is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It contains Sildenafil as its active pharmaceutical ingredient. In addition, it contains other inactive ingredients called excipients in sufficient quantities. It is unclear this product is effective for treating sexual dysfunction in women. It is taken by mouth or injection into a vein.Onset is typically within 20 minutes and lasts for about 2 hours.
Therapeutic Indications and Uses of Si-Vega-Si
When should I take Si-Vega-Si?
Si-Vega-Si is indicated in adult of men with erectile dysfunction, which is the inability to achieve or maintain penile erection sufficient for satisfactory sexual performance. In order for sildenafil to be effective, sexual stimulation is required.
Dosage of Si-Vega-Si
Posology and method of administration
Use in adults
The recommended dose is 50mg taken as needed approximately one hour before sexual activity. Based on efficacy and tolerability, the dose may be increased to 100mg or decreased to 25mg. The maximum recommended dose is 100mg. The maximum recommended dosing frequency is once per day. If sildenafil is taken with food, the onset of activity may be delayed compared to the fasted state.
Dosage adjustments are not required in elderly patients (65 years old).
Patients with renal impairment
The dosing recommendations described in ‘Use in adults’ apply to patients with mild to moderate impairment (creatinine clearance = 30 – 80 ml/min). Since sildenafil clearance is reduced in patients with severe renal impairment (creatinine clearance < 30 ml/min), a 25mg dose should be considered. Based on efficacy and tolerability, the dose may be increased step-wise to 50mg up to 100mg as necessary.
Patients with hepatic impairment
Since sildenafil clearance is reduced in patients with hepatic impairment (e.g. cirrhosis) a 25mg dose should be considered. Based on efficacy and tolerability, the dose may be increased step-wise to 50mg up to 100mg as necessary.
Sildenafil is not indicated for individuals below 18 years of age.
Use in patients taking other medicinal products
With the exception of ritonavir for which co-administration with sildenafil is not advised, starting dose of 25mg should be considered in patients receiving concomitant treatment with CYP3A4 inhibitors. In order to minimize the potential of developing postural hypotension in patients receiving alpha-blocker treatment, patients should be stabilised on alpha-blocker therapy prior to initiating sildenafil treatment. In addition, initiation of sildenafil at a dose of 25mg should be considered.
Interaction of Si-Vega-Si with other medicinal products and other forms of interaction
What drug should I not take while using Si-Vega-Si?
- Hypersensitivity to the active substance or to any of the excipients listed in formulation.
- Consistent with its known effects on the nitric oxide/cyclic guanosine monophosphate (CGMP) pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates, and its co-administration with nitric oxide donors (such as amyl nitrite) or nitrates in any form is therefore contraindicated.
- Agents for the treatment of erectile dysfunction, including sildenafil, should not be used in men for whom sexual activity is inadvisable (e.g. patients with severe cardiovascular disorders such as unstable angina or severe cardiac failure).
- Sildenafil is contraindicated in patients who have loss of vision in one eye because of non-arteritic anterior ischaemic optic neuropathy (NAION), regardless of whether this episode was in connection or not with previous PDE5 inhibitor exposure.
- The safety of sildenafil has not been studied in the following sub groups of patients and its use is therefore contraindicated: severe hepatic impairment, hypotension (blood pressure <90/50 mmHg), recent history of stroke or myocardial infarction and known hereditary degenerative retinal disorders such as retinitis pigmentosa (a minority of these patients has genetic disorders of retinal phosphodiesterases).
Special warnings and precaution of Si-Vega-Si
When should Si-Vega-Si not be used ?
A medical history and physical examination should be undertaken to diagnose erectile dysfunction and determine potential underlying causes, before pharmacological treatment is considered.
Cardiovascular risk factors
Prior to initiating any treatment for erectile dysfunction, physicians should consider the cardiovascular status of their patients, since there is a degree of cardiac risk associated with sexual activity. Sildenafil has vasodilator properties, resulting in mild and transient decreases in blood pressure. Prior to prescribing Sildenafil, physicians should carefully consider whether their patients with certain underlying conditions could be adversely affected by such vasodilatory effects, especially in combination with sexual activity. Sildenafil potentiates the hypotensive effect of nitrates. Serious cardiovascular events, including myocardial infarction, unstable angina, sudden cardiac death, ventricular arrhythmia, cerebrovascular haemorrhage, transient ischaemic attack, hypertension and hypotension have been reported post marketing in temporal association with the use of sildenafil. Most, but not all of these patients had pre existing cardiovascular risk factors. Many events were reported to occur during or shortly after sexual intercourse and a few were reported to occur shortly after the use of sildenafil without sexual activity. It is not possible to determine whether these events are related directly to these factors or other factors.
Agents for the treatment of erectile dysfunction, including sildenafil, should be used with caution in patients with anatomical deformation of the penis (such as angulation, cavernosal fibrosis or Peyronie’s disease), or in patients who have conditions which may predispose them to priapism (such as sickle cell anaemia, multiple myeloma or leukemia)
Concomitant use with other treatments for erectile dysfunction
The safety and efficacy of combinations of sildenafil with other treatments for erectile dysfunction have not been studied. Therefore the use of such combinations is not recommended.
Effects on vision
Cases of visual defects have been reported spontaneously in connection with the intake of sildenafil and other PDES inhibitors. Cases of non-arteritic anterior ischaemic optic neuropathy, a rare condition, have been reported spontaneously and in an observational study in connection with the intake of sildenafil and other PDES inhibitors. Patients should be advised that in the event of any sudden visual defect, they should stop taking sildenafil and consult a physician immediately.
Concomitant use with Ritonavir
Co-administration of Sildenafil with Ritonavir is not advised
Concomitant use with alpha-blockers
Caution is advised when sildenafil is administered to patients taking an alpha-blocker, as the co-administration may lead to symptomatic hypotension in a few susceptible individuals. This is most likely to occur within 4 hours post sildenafil dosing. In order to minimize the potential for developing postural hypotension, patients should be hemodynamically stable on alpha-blocker therapy prior to initiating sildenafil treatment. Initiation of sildenafil at a dose of 25mg should be considered. In addition, physicians should advice patients what to do in the event of postural hypotension symptoms.
Effect on bleeding
Does Sildenafil worsen bleeding?
Studies with human platelets indicate that Sildenafil potentiates the anti-aggregatory effect of sodium nitroprusside in vitro. There is no safety information on the administration of sildenafil to patients with bleeding disorder or active peptic ulceration. Therefore sildenafil should be administered to these patients after careful benefits risk assessment.
Can women take sildenafil?
Sildenafil is not indicated for use by women.
Fertility, pregnancy and lactation:
Is sildenafil safe in pregnancy and lactation?
Sildenafil is not indicated for use by women.
Pharmacology of Si-Vega-Si
Mechanism of action of Si-Vega-Si
Si-Vega-Si is an oral therapy for erectile dysfunction. In natural setting i.e with sexual stimulation, it restores impaired erectile function by increasing blood flow to the penis.The physiological mechanism responsible for erection of the penis involves the release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.
Pharmacodynamic properties of sildenafil
Studies in vitro have shown that sildenafil is selective for PDES, which is involved in the erection process. Its effect is more potent on PDE5 than on other known phosphodiesterase. There there is 10 fold selectivity over PDE6 which is involved in phototransduction pathway in the retina. At maximum recommended doses, there is an 80-fold selectivity over PDE1, and over 700-fold over PDE2, 3,4,7,8,9, 10 and 11. In particular, sildenafil has greater than 4,000-fold selectivity for PDE5 over PDE3, the CAMP-specific phosphodiesterase isoform is involved in the control of cardiac contractility
Pharmacokinetic properties of sildenafil
How is sildenafil absorbed?
Sildenafil is rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. The mean absolute oral bioavailability is 41%(range 25-63%). After oral dosing of sildenafil, AUC and Cmax increase in proportion with dose over the recommended dose range (25-100mg). When sildenafil is taken with food, the rate of absorption is reduced with a mean delay in tmax of 60 minutes and a mean reduction in Cmax of 29%.
The mean steady state volume of distribution (Vd) for sildenafil is 105L, indicating distribution into the tissues. After a single oral dose of 100mg, the mean maximum total plasma concentration of sildenafil is approximately 440 ng/ml (CV 40%). Since Sildenafil (and its major circulating N-desmethyl metabolite) is 96% bound to plasma proteins, this results in the mean maximum free plasma of 18 ng/ml (38 nM). Protein binding is independent of total drug concentrations. In healthy volunteers receiving Sildenafil (100mg single dose), less than 0.0002% (average 188 ng) of the administered dose was present in ejaculate 90 minutes after dosing.
Overdose of Si-Vega-Si
What are the effects of Si-Vega-Si overdose?
In single dose volunteer studies of doses up to 800mg, adverse reactions were similar to those seen at lower doses, but the incidence rates and severities were increased. Doses of 200mg did not result in increased efficacy but the incidence of adverse reactions (headache, flushing, dizziness, dyspepsia, nasal congestion, altered vision) was increased. In cases of overdose, standard supportive measures should be adopted as required. Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and not eliminated in the urine
Side Effects of Si-Vega-Si
What are the side effects of Si-Vega-Si?
Like all medicines, sildenafil can cause side effects in some people. Many people have no side effects or only minor ones.
Common side effects:
Common side effects happen in more than 1 in 100 people.
If you get these side effects, keep taking the medicine, but tell your doctor or pharmacist if these side effects bother you or do not go away:
- feeling sick
- hot flushes, including facial flushing indigestion
- a colour tinge to your vision or blurred vision
- stuffy nose
Serious side effects:
Serious side effects are rare and happen in less than 1 in 1,000 people.
Stop taking sildenafil and call a doctor straight away if you get:
- chest pains – if this happens during or after sex, get into a semi-sitting position and try to relax; do not use nitrates to treat your chest pain
- prolonged and sometimes painful erections – if you have an erection that lasts for more than 4 hours, contact a doctor immediately
- a sudden decrease or loss of vision
- a serious skin reaction – symptoms may include fever, severe peeling and swelling of the skin, blistering of the mouth, genitals and around the eyes
Serious allergic reaction:
In rare cases, it’s possible to have a serious allergic reaction (anaphylaxis) to sildenafil.
Storage of Si-Vega-Si
Store in a cool, dark and dry place out of the reach of children.