Sildenafil Citrate

Introduction

Sildenafil Citrate is a medication primarily used to treat erectile dysfunction (ED) in men. It is also prescribed under the brand name Revatio for the treatment of pulmonary arterial hypertension (PAH). Sildenafil belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors and works by increasing blood flow to specific areas of the body, notably the penis and lungs.

Uses

Sildenafil Citrate is used for the following conditions:

• Erectile Dysfunction (ED): To treat impotence or the inability to achieve or maintain an erection during sexual activity.
• Pulmonary Arterial Hypertension (PAH): To improve exercise ability and delay worsening in patients with PAH by relaxing blood vessels in the lungs.

Brand Name	Sildenafil Citrate
Type
Weight
Generic	Sildenafil Citrate
Manufacturer
Available in	English বাংলা

Mechanism of Action

Sildenafil inhibits phosphodiesterase type 5 (PDE5), an enzyme responsible for the breakdown of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum of the penis. Inhibition of PDE5 leads to increased levels of cGMP, resulting in smooth muscle relaxation, vasodilation, and increased blood flow to the penis during sexual stimulation, facilitating erection. In PAH, Sildenafil relaxes the pulmonary blood vessels, reducing pulmonary arterial pressure.

How Long Does It Take to Work?

For erectile dysfunction, Sildenafil usually begins to work within 30 to 60 minutes of oral administration when taken on an empty stomach. Its effects can last for up to 4-5 hours. For pulmonary arterial hypertension, the onset of action is more gradual, with the effects building over days to weeks of regular use.

Absorption

Sildenafil is rapidly absorbed after oral administration, with peak plasma concentrations occurring within 30 to 120 minutes. Its bioavailability is around 40%. Food, especially high-fat meals, can delay the time to peak concentration but does not affect overall absorption.

Route of Elimination

Sildenafil is metabolized predominantly by the liver enzymes CYP3A4 and CYP2C9. Approximately 80% of the metabolites are excreted in the feces, and around 13% are excreted in the urine.

Dosage

For erectile dysfunction, the typical starting dose of Sildenafil Citrate is 50 mg, taken approximately 1 hour before sexual activity. Based on efficacy and tolerability, the dose may be increased to 100 mg or decreased to 25 mg. The maximum recommended frequency is once daily.

For pulmonary arterial hypertension, the recommended dose is 20 mg taken three times daily, with doses spaced approximately 4-6 hours apart.

Administration

Sildenafil Citrate is administered orally in tablet form. For erectile dysfunction, it should be taken about 30 minutes to 1 hour before anticipated sexual activity, but no more than once daily. For PAH, it is taken regularly, usually three times per day. It is recommended to take the drug with water and to avoid consuming it with a high-fat meal, as this may delay its effectiveness.

Side Effects

Common side effects of Sildenafil include:

• Headache
• Flushing
• Indigestion
• Visual disturbances (blurred vision, blue-tinted vision)
• Nasal congestion
• Dizziness

Serious side effects, though rare, include:

• Priapism (prolonged and painful erection lasting more than 4 hours)
• Severe hypotension
• Sudden vision loss in one or both eyes
• Hearing loss or tinnitus
• Chest pain or irregular heartbeat

Toxicity

An overdose of Sildenafil can result in symptoms such as severe dizziness, fainting, prolonged erection (priapism), or vision changes. Medical attention is required for any overdose symptoms, especially for priapism or severe hypotension. Treatment of overdose may involve supportive care, including cardiovascular monitoring.

Precautions

Sildenafil should be used with caution in patients with cardiovascular conditions, including those with a history of heart attack, stroke, or life-threatening arrhythmia. It is also important to be cautious in patients with low blood pressure or those taking other medications that lower blood pressure. Patients with severe liver or kidney impairment may require dose adjustments.

Interactions

Sildenafil has significant interactions with various medications, including:

• Nitrates: Concurrent use of nitrates (e.g., nitroglycerin) can cause a dangerous drop in blood pressure.
• Alpha-blockers: May lead to symptomatic hypotension.
• CYP3A4 inhibitors: Medications like ketoconazole, erythromycin, and ritonavir can increase sildenafil concentrations, potentially leading to increased side effects.
• Other PDE5 inhibitors: Concurrent use with other PDE5 inhibitors should be avoided due to an increased risk of adverse effects.

Disease Interaction

Sildenafil should be used cautiously in patients with the following conditions:

• Cardiovascular disease, particularly in those with unstable angina or severe heart failure
• Retinitis pigmentosa, a genetic eye condition
• Peptic ulcer disease
• Severe renal or hepatic impairment

Drug Interaction

Significant drug interactions may occur with:

• Nitrates: Severe hypotension when used with sildenafil.
• Antihypertensives: Additive blood pressure-lowering effects.
• CYP3A4 inhibitors: Increased risk of side effects due to reduced sildenafil metabolism.
• Protease inhibitors: May increase sildenafil levels, necessitating dose adjustments.

Food Interactions

Taking Sildenafil with a high-fat meal can delay the onset of action by reducing absorption. It is recommended to take the drug on an empty stomach for faster results. Alcohol consumption may exacerbate the risk of side effects such as dizziness and hypotension.

Pregnancy Use

Sildenafil is not indicated for use in women, particularly during pregnancy. Its safety and efficacy have not been established for pregnant women, and it should only be used if prescribed for pulmonary arterial hypertension, where the potential benefit outweighs the risk to the fetus.

Lactation Use

Sildenafil is not recommended for use during breastfeeding due to the lack of studies regarding its excretion in breast milk. Its use should be limited to cases of pulmonary arterial hypertension, and a healthcare provider should evaluate the potential risks and benefits.

Acute Overdose

Acute overdose of Sildenafil can result in severe side effects, including prolonged erections (priapism), dizziness, fainting, hypotension, or visual disturbances. Medical treatment is required in case of overdose, and supportive care, such as fluids and cardiovascular monitoring, may be necessary.

Contraindication

Sildenafil is contraindicated in patients who:

• Are taking nitrates for chest pain (angina)
• Have a known hypersensitivity to sildenafil or any of the formulation's components
• Have severe cardiovascular disease or have had a recent heart attack or stroke
• Have severe liver impairment

Use Direction

Sildenafil should be taken as directed by a healthcare provider. For erectile dysfunction, it is usually taken as needed, about 30 minutes to 1 hour before sexual activity. It should not be taken more than once in 24 hours. For pulmonary arterial hypertension, it is taken three times a day at regular intervals. Avoid consuming grapefruit or grapefruit juice as it may affect the metabolism of the drug.

Storage Conditions

Sildenafil should be stored at room temperature (20-25°C or 68-77°F) in a dry place away from moisture and heat. It should be kept out of reach of children.

Volume of Distribution

The volume of distribution for Sildenafil is approximately 105 L, indicating that the drug distributes widely into tissues.

Half Life

The half-life of Sildenafil is approximately 3-5 hours. For most patients, the drug's effects diminish after 4-5 hours, although it may linger longer in some individuals.

Clearance

Sildenafil is primarily cleared by hepatic metabolism via the CYP3A4 enzyme. Its clearance rate is influenced by liver and kidney function, and patients with impaired hepatic or renal function may have reduced clearance and prolonged effects.

See in details version Sildenafil Citrate also Sildenafil Citrate in bangla

Some Frequently Asked Questions About Sildenafil Citrate

1. What is Sildenafil Citrate ?

Sildenafil Citrate is a medication primarily used to treat erectile dysfunction (ED) in men and pulmonary arterial hypertension (PAH). It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors.

2. How does Sildenafil Citrate work?

It works by relaxing blood vessels and increasing blood flow to specific areas of the body, such as the penis during sexual stimulation (for ED) or the lungs (for PAH).

3. What is Sildenafil Citrate commonly known as?

It is most commonly known by its brand name, Viagra, though generic versions are also widely available.

4. What conditions does Sildenafil treat?

Sildenafil is used to treat:

• Erectile dysfunction (ED)
• Pulmonary arterial hypertension (PAH)

5. Is Sildenafil Citrate safe for everyone?

No, it is not safe for everyone. People with certain medical conditions (e.g., severe heart disease) or those taking specific medications (e.g., nitrates) should avoid it. Consult a doctor first.

6. How long does Sildenafil take to work?

It typically takes 30 to 60 minutes to start working for ED, though this can vary based on food intake and individual response.

7. How long does Sildenafil last?

Its effects can last for 4 to 6 hours, though this depends on the individual and dosage.

8. Can women take Sildenafil Citrate ?

Sildenafil is not approved for women with sexual dysfunction, but it may be prescribed off-label in some cases for PAH. Women should consult a doctor.

9. What is the typical dosage for ED?

The typical starting dose for ED is 50 mg, taken as needed about 1 hour before sexual activity. Dosage can range from 25 mg to 100 mg based on doctor’s advice.

10. Can I take Sildenafil every day?

For ED, it’s usually taken as needed, not daily. For PAH, it may be prescribed daily under medical supervision.

11. Does food affect Sildenafil?

Yes, a high-fat meal can delay its absorption and reduce its effectiveness. It’s best taken on an empty stomach.

12. Can I drink alcohol with Sildenafil?

Moderate alcohol is usually fine, but excessive drinking may reduce its effectiveness and worsen ED.

13. What are common side effects of Sildenafil?

Common side effects include:

• Headache
• Flushing
• Indigestion
• Nasal congestion
• Dizziness

14. Are there serious side effects?

Yes, rare but serious side effects include:

• Prolonged erection (priapism)
• Sudden vision loss
• Sudden hearing loss
• Chest pain

Seek medical help if these occur.

15. What is priapism?

Priapism is a prolonged erection lasting more than 4 hours, which can damage the penis if untreated. It’s a medical emergency.

16. Can Sildenafil cause vision changes?

Yes, some people experience temporary changes like blurred vision or a blue tint. Rare cases involve sudden vision loss.

17. Is Sildenafil addictive?

No, Sildenafil is not physically addictive, though some may develop a psychological reliance on it for confidence.

18. Can I buy Sildenafil without a prescription?

In most countries, Sildenafil requires a prescription. Over-the-counter versions exist in some places (e.g., Viagra Connect in the UK), but consult a pharmacist or doctor.

19. Is generic Sildenafil as effective as Viagra?

Yes, generic Sildenafil contains the same active ingredient and is equally effective when produced by reputable manufacturers.

20. How should I store Sildenafil?

Store it at room temperature (15-30°C or 59-86°F), away from moisture, heat, and direct sunlight.

21. Can I split Sildenafil tablets?

Only if your doctor advises it and the tablet isn’t film-coated or scored. Check with a pharmacist.

22. What happens if I overdose on Sildenafil?

An overdose can cause severe side effects like low blood pressure, fainting, or priapism. Seek emergency medical help.

23. Can I take Sildenafil with nitrates?

No, combining Sildenafil with nitrates (e.g., nitroglycerin) can cause a dangerous drop in blood pressure.

24. Does Sildenafil increase sexual desire?

No, it doesn’t affect libido. It only helps achieve an erection with sexual stimulation.

25. Who should not take Sildenafil?

People who should avoid it include:

• Those on nitrates
• Those with severe liver or kidney disease
• Those with certain eye conditions (e.g., retinitis pigmentosa)

26. Can Sildenafil treat premature ejaculation?

It’s not designed for this, but some studies suggest it may help indirectly by improving erection confidence.

27. Is Sildenafil safe for older adults?

Yes, but older adults may need a lower dose (e.g., 25 mg) due to slower metabolism. Consult a doctor.

28. Can I take Sildenafil with other ED drugs?

No, combining it with other PDE5 inhibitors (e.g., Cialis, Levitra) is dangerous and not recommended.

29. Does Sildenafil affect fertility?

No evidence suggests it impacts sperm count or fertility in men.

30. Can I take Sildenafil if I have diabetes?

Yes, it’s often safe for diabetics with ED, but a doctor should evaluate your overall health first.

31. What’s the difference between Sildenafil and Tadalafil?

Sildenafil (Viagra) lasts 4-6 hours, while Tadalafil (Cialis) lasts up to 36 hours. They’re both PDE5 inhibitors but differ in duration.

32. Can Sildenafil cause heart problems?

It’s generally safe for healthy hearts but can strain the heart during sex if you have pre-existing cardiovascular issues.

33. How was Sildenafil discovered?

It was originally developed by Pfizer to treat angina (chest pain) but was found to improve erections during clinical trials.

34. Is Sildenafil approved by the FDA?

Yes, it was approved by the FDA in 1998 for ED and later for PAH under the brand Revatio.

35. What’s Revatio?

Revatio is a brand of Sildenafil used to treat PAH, typically in lower doses (20 mg) than Viagra.

36. Can Sildenafil be used recreationally?

It’s not recommended for those without ED, as it won’t enhance performance beyond normal function and carries risks.

37. Does Sildenafil expire?

Yes, check the expiration date on the package. Expired Sildenafil may be less effective or unsafe.

38. Can I take Sildenafil with blood pressure medication?

Some are safe, but it depends on the type. Avoid it with alpha-blockers or nitrates unless approved by a doctor.

39. Does Sildenafil affect sleep?

It’s not known to directly affect sleep, though side effects like headache or flushing might disrupt rest.

40. Can Sildenafil be taken long-term?

Yes, for PAH it’s used long-term. For ED, long-term use is safe if prescribed and monitored.

41. What’s the maximum dose of Sildenafil?

For ED, the maximum recommended dose is 100 mg per day. Higher doses increase side effect risks.

42. Can Sildenafil cause allergic reactions?

Yes, though rare. Symptoms include rash, itching, or swelling. Seek help if this occurs.

43. Is Sildenafil safe during pregnancy?

It’s not typically prescribed to pregnant women unless for PAH, and only under strict medical supervision.

44. Can I drive after taking Sildenafil?

Yes, unless you experience dizziness or vision changes, in which case you should avoid driving.

45. Does Sildenafil interact with grapefruit?

Yes, grapefruit can increase Sildenafil levels in the blood, raising the risk of side effects.

46. Can teenagers take Sildenafil?

It’s not approved for those under 18 unless prescribed for PAH in rare cases.

47. What’s the cost of Sildenafil?

Generic Sildenafil is typically cheaper than Viagra, ranging from $0.50 to $10 per pill, depending on location and dosage.

48. Can Sildenafil be crushed?

It’s not recommended unless your doctor or pharmacist says it’s safe for your specific tablet type.

49. Does Sildenafil work without stimulation?

No, sexual arousal is needed for it to work—it doesn’t cause spontaneous erections.