Sildenafil Uses, Dosage, Side Effects, Food Interaction and all others data.

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.

In vitro studies have shown that sildenafil is selective for phosphodiesterase-5 (PDE5) . Its effect is more potent on PDE5 than on other known phosphodiesterases . In particular, there is a 10-times selectivity over PDE6 which is involved in the phototransduction pathway in the retina . There is an 80-times selectivity over PDE1, and over 700-times over PDE 2, 3, 4, 7, 8, 9, 10 and 11 . And finally, sildenafil has greater than 4,000-times selectivity for PDE5 over PDE3, the cAMP-specific phosphodiesterase isoform involved in the control of cardiac contractility .

In eight double-blind, placebo-controlled crossover studies of patients with either organic or psychogenic erectile dysfunction, sexual stimulation resulted in improved erections, as assessed by an objective measurement of hardness and duration of erections (via the use of RigiScan®), after sildenafil administration compared with placebo . Most studies assessed the efficacy of sildenafil approximately 60 minutes post-dose . The erectile response, as assessed by RigiScan®, generally increased with increasing sildenafil dose and plasma concentration . The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours .

Sildenafil causes mild and transient decreases in systemic blood pressure which, in the majority of cases, do not translate into clinical effects . After chronic dosing of 80 mg, three times a day to patients with systemic hypertension the mean change from baseline in systolic and diastolic blood pressure was a decrease of 9.4 mmHg and 9.1 mmHg respectively . After chronic dosing of 80 mg, three times a day to patients with pulmonary arterial hypertension lesser effects in blood pressure reduction were observed (a reduction in both systolic and diastolic pressure of 2 mmHg) . At the recommended dose of 20 mg three times a day no reductions in systolic or diastolic pressure were seen .

Trade Name Sildenafil
Availability Prescription only
Generic Sildenafil
Sildenafil Other Names Sildenafil, Sildenafilo
Related Drugs tadalafil, Viagra, Cialis, alprostadil, Levitra, vardenafil, Revatio, Adempas, Opsumit, ambrisentan
Weight 10mg/12.5ml, , 50mg, 100mg
Type Powder, For Oral Suspension, Tablet, Film Coated, Intravenous, Intravenous Solution, Injection, Tablet 100 Mg
Formula C22H30N6O4S
Weight Average: 474.576
Monoisotopic: 474.204924168
Protein binding

It is generally observed that sildenafil and its main circulating N-desmethyl metabolite are both estimated to be about 96% bound to plasma proteins . Nevertheless, it has been determined that protein binding for sildenafil is independent of total drug concentrations .

Groups Approved, Investigational
Therapeutic Class Drugs for Erectile Dysfunction
Manufacturer Aurobindo Pharma - Milpharm Ltd, , Novell Pharmaceutical Lab Indonesia, Impulse Pharma Pvt Limited, Relax Biotech Pvt Ltd, Frendun Pharmaceuticals Ltd, Mancare Pharmaceuticals Pvt Ltd, Lesanto Laboratories Ltd
Available Country United Kingdom, United States, Netherlands, Indonesia, India, Nigeria
Last Updated: September 19, 2023 at 7:00 am


Sildenafil Citrate is used for the treatment of Erectile Dysfunction.

Sildenafil is also used to associated treatment for these conditions: Erectile Dysfunction, NYHA Functional Class II-III Pulmonary arterial hypertension, Premature Ejaculation, Symptomatic pulmonary arterial hypertension (PAH)

How Sildenafil works

Sildenafil is an oral therapy for erectile dysfunction . In the natural setting, i.e. with sexual stimulation, it restores impaired erectile function by increasing blood flow to the penis .

The physiological mechanism responsible for the 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 .

Sildenafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum, where PDE5 is responsible for degradation of cGMP . Sildenafil has a peripheral site of action on erections . Sildenafil has no direct relaxant effect on isolated human corpus cavernosum but potently enhances the relaxant effect of NO on this tissue . When the NO/cGMP pathway is activated, as occurs with sexual stimulation, inhibition of PDE5 by sildenafil results in increased corpus cavernosum levels of cGMP . Therefore sexual stimulation is required in order for sildenafil to produce its intended beneficial pharmacological effects .

Moreover, apart from the presence of PDE5 in the corpus cavernosum of the penis, PDE5 is also present in the pulmonary vasculature . Sildenafil, therefore, increases cGMP within pulmonary vascular smooth muscle cells resulting in relaxation . In patients with pulmonary arterial hypertension, this can lead to vasodilation of the pulmonary vascular bed and, to a lesser degree, vasodilatation in the systemic circulation .


Sildenafil dosage

The usual starting dose of Sildenafilis 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.

Sildenafil may takes longer time to work if you take it with a heavy meal.

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.


In single-dose volunteer studies of doses up to 800 mg, adverse reactions were similar to those seen at lower doses, but the incidence rates and severities were increased . Doses of 200 mg did not result in increased efficacy but the incidence of adverse reaction (headache, flushing, dizziness, dyspepsia, nasal congestion, altered vision) was increased .

Due to the lack of data on the effect of sildenafil indicated for the treatment of pulmonary arterial hypertension (PAH) in pregnant women, sildenafil is not recommended for women of childbearing potential unless also using appropriate contraceptive measures .

The safety and efficacy of sildenafil indicated for treating PAH in a woman during labor and delivery have not been studied . Caution should ultimately be exercised when sildenafil is administered to nursing women as it is not known if sildenafil or its metabolites are excreted in human breast milk .

The safety and efficacy of sildenafil for the treatment of PAH in children below 1 year of age has not been established as no data is available .

Clinical experience with the elderly population in the use of sildenafil for the treatment of PAH has been varied. Some reports suggest that there are no identified differences in responses between elderly and younger patients while others have documented that clinical efficacy as measured by 6-minute walk distance could be less in elderly patients . In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy .

Conversely, when sildenafil was used to treat erectile dysfunction in healthy elderly volunteers (65 years or over), a reduced clearance of sildenafil was observed . This reduction resulted in about 90% higher plasma concentrations of sildenafil and the active N-desmethyl metabolite compared to those seen in healthy younger volunteers (18-45 years) . Due to age-differences in plasma protein binding, the corresponding increase in free sildenafil plasma concentration was approximately 40% .

Sildenafil was not carcinogenic when administered to rats for 24 months at a dose resulting in total systemic drug exposure (AUCs) for unbound sildenafil and its major metabolite of 29- and 42- times, for male and female rats, respectively, the exposures observed in human males given the Maximum Recommended Human Dose (MRHD) of 100 mg . Sildenafil was not carcinogenic when administered to mice for 18-21 months at dosages up to the Maximum Tolerated Dose (MTD) of 10 mg/kg/day, approximately 0.6 times the MRHD on a mg/m2 basis .

Sildenafil was negative in in vitro bacterial and Chinese hamster ovary cell assays to detect mutagenicity, and in vitro human lymphocytes and in vivo mouse micronucleus assays to detect clastogenicity .

There was no impairment of fertility in rats given sildenafil up to 60 mg/kg/day for 36 days to females and 102 days to males, a dose producing an AUC value of more than 25 times the human male AUC .


Warnings: In patients with preexisting cardiovascular disease, there is a potential risk in sexual activity. Sildenafil should not be generally used in men for whom sexual activity is inadvisable because of their underlying cardiovascular status. Sildenafil has systemic vasodilatory properties (mean maximum decrease of 8.4/5.5 mmHg). Patients with left ventricular outflow obstruction (e.g. aortic stenosis, idiopathic hypertrophic subaortic stenosis) and those with severely impaired autonomic control of blood can be particularly sensitive to the actions of vasodilators including Sildenafil.There is no controlled clinical data on the safety or efficacy of Sildenafil in Patients who have suffered from a myocardial infarction, stroke, or life-threatening arrhythmia within the last 6 months. Caution should be taken in patients with resting hypotension (BP <90/50) or hypertension (BP >170/110), cardiac failure or coronary artery disease causing unstable angina, retinitis pigmentosa. Prolonged erection greater than 4 hours and priapism (painful erections greater than 6 hours in duration) have been reported infrequently since market approval of Sildenafil. In this situation, patient should seek immediate medical assistance.

Precautions: Please tell your doctor or pharmacist if you are taking or have recently taken other medicines, including medicines obtained without prescription. Sildenafil tablets may interfere with some medicines, especially those used to treat chest pain. In the event of a medical emergency, you should tell the healthcare professional treating your condition that you have taken Sildenafil and if you did, do not take Sildenafil with other medicines unless your doctor tells you can.You should not take Sildenafil if you are taking medicines called nitrates as the combination of these products may cause a potentially dangerous decrease in your blood pressure. Always tell your doctor or pharmacist if you are taking any of these medicines that are often used for the relief of angina pectoris (or chest painJ.You should not take Sildenafil if you are using any of the drugs known as nitric oxide donors such as amyl nitrite as the combination may also lead to potentially dangerous decrease in your blood pressure. If you are taking medicines known as protease inhibitors, such as for the treatment of HIV, your doctor may start you on the lowest dose (25 mg) of Sildenafil. Some patients who take alpha-blocker therapy for the treatment of high blood pressure or prostate enlargement may experience dizziness or light-headedness, which may be caused by low blood pressure upon sitting or standing up quickly. Certain patients have experienced these symptoms when taking Sildenafil with alpha-blocker. This is most likely to occur within 4 hours after taking Sildenafil. In order to reduce the likelihood of these symptoms occur,you should be on a regular daily dose of your alpha-blocker before you start Sildenafil. Your doctor may start you on a lower dose (2S mg) of Sildenafil if you have hypotension (avoid if systolic blood pressure below 90 mmHg), recent stroke, unstable angina & myocardial infarction. Drinking alcohol can temporally impair your ability to get an erection, to get the maximum benefit from your medicine; you are advised not to drink excessive amounts of alcohol before taking Sildenafil.


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.

Food Interaction

  • Take with or without food. If taken with a high-fat meal the medicine may take a little longer to start working.

[Moderate] GENERALLY AVOID: Coadministration with grapefruit juice may slightly increase the oral bioavailability and delay the onset of action of sildenafil.

The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

In a randomized, crossover study with 24 healthy male volunteers, ingestion of 250 mL of grapefruit juice one hour before and concurrently with a 50 mg dose of sildenafil increased the mean area under the plasma concentration-time curve (AUC) of sildenafil and its pharmacologically active N-desmethyl metabolite by 23% and 24%, respectively, compared to water.

Peak plasma concentrations (Cmax) were unaltered, but the time to reach sildenafil Cmax was prolonged by 0.25 hour.

The observed increase in sildenafil bioavailability is unlikely to be of clinical significance in most individuals.

However, pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability and may be significant in the occasional susceptible patient.

Indeed, one subject in the study had a 2.6-fold increase in sildenafil concentrations.

MANAGEMENT: It may be advisable to avoid administration of sildenafil with grapefruit juice to prevent potential toxicity and delay in onset of action.

Sildenafil Alcohol interaction


Additive hypotensive effects may occur when phosphodiesterase-5 (PDE5) inhibitors are used with alcohol, as both are mild systemic vasodilators.

In clinical pharmacology studies, more subjects administered alcohol at a dose of 0.7 g/kg (equivalent to approximately 6 ounces of 80-proof vodka in an 80-kg male; consumed within 10 minutes in study subjects, providing blood alcohol levels of 0.08%) in combination with tadalafil 10 or 20 mg single doses had clinically significant decreases in blood pressure than with alcohol alone.

There were reports of postural dizziness, and orthostatic hypotension was observed in some.

When tadalafil 20 mg was administered with alcohol at a lower dose of 0.6 g/kg (equivalent to approximately 4 ounces of 80-proof vodka in an 80-kg male), orthostatic hypotension was not observed, dizziness occurred with similar frequency relative to alcohol alone, and the hypotensive effects of alcohol were not potentiated.

Neither tadalafil nor alcohol affected the plasma concentrations of the other.

Administration of avanafil 200 mg with alcohol at a dose of 0.5 g/kg (equivalent to approximately 3 ounces of 80-proof vodka in a 70-kg male; consumed within 15 minutes in study subjects, providing blood alcohol levels of 0.057%) resulted in additional maximum supine systolic/diastolic blood pressure decreases of 3.5/4.5 mm Hg and additional maximum pulse rate increase of 9.3 bpm compared to alcohol alone, but did not cause orthostatic hypotension or dizziness.

The plasma concentrations of alcohol were not affected.

Sildenafil 50 mg and vardenafil 20 mg reportedly did not potentiate the hypotensive effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 0.08% and in healthy volunteers administered alcohol at a dose of 0.5 g/kg, respectively.

Alcohol and vardenafil plasma levels were not altered when dosed simultaneously.

Patients taking PDE5 inhibitors should avoid consuming large amounts of alcohol, which may increase the potential for orthostatic signs and symptoms including increase in heart rate, decrease in standing blood pressure, dizziness, and headache.

Volume of Distribution

The mean steady-state volume of distribution documented for sildenafil is approximately 105 L - a value which suggests the medication undergoes distribution into the tissues .

Elimination Route

Sildenafil is known to be quickly absorbed, with maximum plasma concentrations being observed within 30-120 minutes (with a median of 60 minutes) of oral administration in a fasting patient . Moreover, the mean absolute bioavailability observed for sildenafil is about 41% (from a range of 25-63%) . In particular, after oral three times a day dosing of sildenafil, the AUC and Cmax increase in proportion with dose over the recommended dosage range of 25-100 mg .

When used in pulmonary arterial hypertension patients, however, the oral bioavailability of sildenafil after a dosing regimen of 80 mg three times a day, was on average 43% greater than compared to the lower doses .

Finally, if sildenafil is administered orally with food, the rate of absorption is observed to be decreased with a mean delay in Tmax of about 60 minutes and a mean decrease in Cmax of approximately 29% . Regardless, the extent of absorption is not observed to be significantly affected as the recorded AUC decreased by only about 11 % .

Half Life

The terminal phase half-life observed for sildenafil is approximately 3 to 5 hours .


The total body clearance documented for sildenafil is 41 L/h .

Elimination Route

After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose) .

Pregnancy & Breastfeeding use

Sildenafil is not indicated for use in newborns, children & women.


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.

Acute Overdose

In studies with healthy volunteers of single doses up to 800 mg, adverse events were similar to those seen at lower doses but incidence rates and severities were 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 it is not eliminated in the urine.

Storage Condition

Store below 30° C. Protect from light and moisture. Keep out of reach of children.

Innovators Monograph

You find simplified version here Sildenafil

Sildenafil contains Sildenafil see full prescribing information from innovator Sildenafil Monograph, Sildenafil MSDS, Sildenafil FDA label


What is Sildenafil used for?

Sildenafil is a medicine used to treat erectile dysfunction. It increases blood flow to the penis to help men get an erection.

How safe is Sildenafil?

The most common side effects are headaches, feeling sick, hot flushes and dizziness. Many men have no side effects or only mild ones. It can be dangerous to take Sildenafil if you also take medicines called nitrates. The combination can cause a dangerous fall in your blood pressure.

How does Sildenafil work?

Sildenafil works by preventing the action of a chemical in your body, called phosphodiesterase type-5. This helps to widen blood vessels and improves the flow of blood to the penis following sexual stimulation. This helps to maintain an erection.

What are the common side effects of Sildenafil?

The most common side effects are headaches, feeling sick, hot flushes and dizziness. Many men have no side effects or only mild ones. It can be dangerous to take Sildenafil if you also take medicines called nitrates. The combination can cause a dangerous fall in your blood pressure.

What should I avoid when taking Sildenafil?

If you are receiving therapy with Sildenafil you should avoid the regular consumption of large amounts of grapefruits and grapefruit juice. Grapefruit can raise the levels of Sildenafil in your body and delay the time it takes for the medication to work.

Is Sildenafil safe during pregnancy?

This drug is not indicated for use in women. Safety has not been established.This drug should be used only if clearly needed.There are risks to the mother and fetus from untreated pulmonary arterial hypertension.

Is Sildenafil safe during breastfeeding?

Limited data indicate that Sildenafil and its active metabolite in breastmilk are poorly excreted into breastmilk. Amounts ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants.

Does Sildenafil work for females?

It's not approved for sexual dysfunction in women , yet, though some may use it.

Can I take Sildenafil when trying for a baby?

There are reports that Sildenafil can cause sperm damage in exceedingly rare cases. However the chances of this happening are minute. It is far more likely for Sildenafil to positively affect fertility, by helping you gain and maintain an erection.

Can Sildenafil affect my partner?

Sildenafil use resulted in a male partner's ability to have multiple erections over 12–24 hours

What happens if a girl takes Sildenafil?

Sildenafil dilates blood vessels and increases the flow of blood to the penis. Women who take it might also have increased blood flow to the genitals. That may help increase sensitivity, arousal, and orgasmic function.

How long does Sildenafil last in the body?

Sildenafil has a half-life of about three to four hours. This simply means that the active amount of Sildenafil in your body reduces by around half after three to four hours.

Does Sildenafil make me last longer?

There isn't conclusive scientific evidence that Sildenafil can make you last longer, but some studies suggest it might.

Who should not take Sildenafil?

If you have significant uncontrolled high blood pressure you can not take Sildenafil. 

Does Sildenafil affect fertility?

Sildenafil does not alter semen parameters, and, in fact, may positively affect semen parameters. Sildenafil is helpful for treating ED caused by the psychological stress of infertility treatments. Sildenafil has improved the treatment of ED and may have a benefit on semen parameters.

Does Sildenafil make me bigger?

Sildenafil will not make your penis physically larger than its regular size even if you take a higher dose.

Can I take sildenafil everyday?

The short answer is yes; you can take Sildenafil every day.

How should I take sildenafil for best results?

Take Sildenafil at least 30 minutes, but no more than 4 hours, before sexual activity.

Does Sildenafil stop I Cumming?

Sildenafil is not an effective treatment for premature ejaculation, meaning it usually won't have any effect on the amount of time for which you can have sex before you ejaculate, the amount of sensitivity you experience during sex or when you orgasm and ejaculate.

Can I take Sildenafil with milk?

You can take Sildenafil with a glass of water, but you can also take it with milk or a light snack.

Can I drink alcohol with Sildenafil?

It's best to avoid consuming alcohol while taking ED medications like Viagra: Not only can alcohol counteract the medication's effects, but it can also worsen side effects, like flushing and headaches. Again, talk to your healthcare provider before drinking alcohol if you're taking medications like Sildenafil.

If I overdose of Sildenafil?

An overdose of Sildenafil may theoretically result in hypotension, tachycardia and cardiac arrest.

*** Taking medicines without doctor's advice can cause long-term problems.