Indications
Sildenafil Citrate is indicated for the treatment of Erectile Dysfunction.
Therapeutic Class
Drugs for Erectile Dysfunction
Pharmacology
Sildenafil Citrate belongs to a group of medicines called phosphodiesterase type-5 (PDE-5) inhibitors. It works by helping to relax the blood vessels of penis, allowing blood to flow into penis. The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO 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. When sexual stimulation causes local release of NO, inhibition of PDE-5 by sildenafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation.
Dosage
The usual starting dose of Sildenafil is 50 mg once daily. lt should be taken before 30-40 minutes of intercourse. Depending on effectiveness and tolerance; the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum dosing frequency is once per day.Some factors are associated with increased plasma levels of sildenafil: age>65, hepatic impairment, severe renal impairment and concomitant use of ketoconazole, itraconazole, erythromycin. Since higher plasma levels may increase both the efficacy and incidence of adverse events, a starting dose of 25 mg should be considered in these patients.
Administration
Sildenafil may takes longer time to work if you take it with a heavy meal.
Interaction
Inhibitors of CYP3A4 such as cimetidine and erythromycin are likely to reduce sildenafil clearance. CYP3A4 inducers such as rifampicin may decrease the plasma concentrations of sildenafil. Symptomatic hypotension when used with α-blockers. Plasma concentrations are increased by ritonavir.
Contraindications
Sildenafil was shown to potentiate the hypotensive effects of nitrates and its administration to patients who are using organic nitrates, either regularly and or intermittently, in any form is therefore contraindicated.
Side Effects
Like all medicines, Sildenafil can cause side effects although not everybody gets them.The side effects reported in association with the use of Sildenafil are usually mild to moderate and of a short duration. All medicines including Sildenafil can cause allergic reactions.Contact with doctors immediately if experiences any of the following symptoms after taking Sildenafil: sudden wheeziness, difficulty in breathing or dizziness, swelling of the eyelids, face, lips or throat. Common side effect includes headache, facial flushing, indigestion, effects on vision, light sensitivity, blurred vision or reduced, stuffy nose and dizziness. Uncommon side effect includes vomiting, skin rash, bleeding at the back of the eye, red eyes, eye pain, double vision, abnormal sensation in the eye, irregular or rapid heartbeat, muscle pain, feeling sleepy, reduced sense of touch, vertigo, ringing in the ears, nausea, dry mouth, chest pain & feeling tired.
Pregnancy & Lactation
Sildenafil is not indicated for use in newborns, children & women.
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