Sildenafil Citrate

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Post Uploaded Date : January 26, 2024 Last Updated Date : March 6, 2024
Sildenafil Citrate
Sildenafil is a salt licensed by the FDA in 1998 for the treatment of erectile dysfunction. All variants or generic versions of Viagra have sildenafil citrate as the primary active ingredient.
 Sildenafil salt is also known as a PDE5 inhibitor due to its ability to suppress the activity of the phosphodiesterase enzyme, which is responsible for eliminating the cGMP molecule required for obtaining and sustaining an erection.
Available in brand names such as Cenforce and Vidalista, it works within 30 minutes of intake. 

Erectile dysfunction is a condition defined by the inability to get and keep an erection, which is estimated to affect up to 30 million men in the United States, as reported by the New England Journal of Medicine [1]. Thus, it is becoming one of the most common pharmaceutical challenges at the present time.

One of the most frequently available treatments for ED includes Sildenafil tablets. This blog takes men’s sexual health into account and thus looks into the use of Sildenafil for Erectile Dysfunction along with its health risks and precautionary measures.

What Is Sildenafil?

Sildenafil is used in the management and treatment of Erectile dysfunction.

Sildenafil compound was initially synthesized in 1989 by researchers at Pfizer working on treatments for cardiovascular disease. It was found to inhibit the enzyme PDE5, which regulates blood flow. 

In 1991, clinical trials began testing sildenafil citrate (Viagra) for erectile dysfunction (ED). It was found to significantly improve ED by enhancing blood flow to the penis during arousal.

Pfizer filed for a patent on sildenafil for the treatment of ED in 1994. It was approved for medical use in the United States on March 27, 1998, under the brand name Viagra.

Viagra became the first oral medication approved to treat Erectile Dysfunction in the United States, becoming a US $1.934 billion market in 2008. 

When Viagra’s patent expired in 2012, it allowed generic manufacturers to produce Sildenafil tablets without permission from Pfizer. This led to a dramatic drop in the price of sildenafil pills and allowed other pharmaceutical companies to develop medicines containing the same active compound and sell them under a different trade name.

Sildenafil Brand Name

In June 2013, the first FDA-approved generic version of Viagra was launched in the US by Teva Pharmaceuticals. The popular brand names approved by the FDA include Cenforce, Aurogra, Malegra, Fildena, and Kamagra. They contain the same active ingredient but vary in inactive ingredients, dosages, prices, and shapes.

Today, Sildenafil, also popularly known as generic Viagra, remains the most common medication used worldwide for erectile dysfunction treatment. It generates billions in sales annually, both from branded Viagra and its generic versions.

Sildenafil Brand Names Manufacturer
Revatio Pfizer Inc.
Cenforce Centurion Laboratories
Aurogra Aurochem Laboratories
Malegra Sunrise Remedies
Eriacta Ranbaxy Laboratories
Fildena Fortune Healthcare

Cenforce tablets are available in the following dosage strengths at Vedi Care-

  • Cenforce 100 mg tablets
  • Cenforce 150 mg tablets
  • Cenforce 200 mg tablets

On the other hand, Cenforce Professional is a sublingual Erectile dysfunction medication that helps in getting erections in people with swallowing disorders.

It is essential to note that Sildenafil or Viagra does not cure Erectile Dysfunction but only treats its symptoms

Shelf Life Of Sildenafil

 It has a shelf life of about 2 years. After its expiration date, the potency of the medication reduces, along with increasing the risk of experiencing side effects. Such tablets may also have bacterial or mold growth on their surface. Thus, it is always advisable to check the expiration date of the medication before administration. 

Mechanism Of Action- How Does Sildenafil Citrate Work?

Sildenafil works by blocking or reducing the activity of an enzyme called phosphodiesterase type 5 (PDE5). This enzyme usually breaks down a molecule called cyclic guanosine monophosphate (cGMP), which is essential for relaxing the muscles of the body. 

By reducing the activity of the PDE5 enzyme, Sildenafil increases the level of cGMP in the penile area, leading to muscle relaxation in the abdomen, which is important for treating conditions like erectile dysfunction.

This thus helps improve the flow of blood, resulting in a better and firmer erection. 

Sildenafil works within 12 to 30 minutes of intake, and its action lasts for at least 4 hours. 

Sildenafil Half-Life

Sildenafil has a half-life of 4 hours, which is the amount of time it takes for the medication’s active component to reduce by half. The half-life of a compound also determines the dosage frequency and how long Sildenafil stays in the system. 

Sildenafil Pill Identifier

The Sildenafil tablets are white to off-white in color. These are oval-shaped tablets with  ‘AN 355’ debossing on one side of the pill and plain on the other side. They may also be available in blue, depending on the manufacturer. 

Sildenafil Prescriptions and Requirements

Cardiologists may prescribe the use of Sildenafil to patients suffering from ED associated with coronary disease. Other doctors, such as endocrinologists, may also prescribe this medication after evaluating your condition. 

A physician may prescribe Sildenafil to people to manage symptoms of Erectile dysfunction resulting from the following health conditions-

  • Type 2 Diabetes
  • High Blood Pressure
  • Multiple Sclerosis
  • Atherosclerosis.

Sildenafil Uses

Apart from treating erectile dysfunction, on November 20, 2009, it was further approved by the FDA for treating pulmonary hypertension (also known as pulmonary arterial hypertension (PAH)) in adults. 

The off-label uses of Sildenafil include treating secondary Raynaud phenomena and as an adjunct treatment option for altitude-induced hypoxemia.

Sildenafil For Women

Sildenafil tablets are not often prescribed to women as they are primarily used to treat erectile dysfunction. However, its use in women is recommended for treating pulmonary arterial hypertension (PAH). 

In many cases, Sildenafil, along with its brand drugs, is used off-label to treat low sex drive in women, also known as “female sexual interest or arousal disorder (FSIAD). 

Medical professionals may further prescribe Sildenafil to treat FSIAD arising from the use of antidepressants such as serotonin-norepinephrine reuptake inhibitors and selective serotonin reuptake inhibitors. 

Sildenafil For Dogs

Similar to humans, Sildenafil is prescribed to dogs and cats to treat pulmonary arterial hypertension (PAH). Its use has been shown to improve exercise tolerance, energy, and the overall quality of life in animals with PAH. 

Sildenafil Dose For Erectile Dysfunction

The Sildenafil tablets are available in 25mg, 50 mg, and 100 mg strengths. Beginners are advised to start with a lower dose of the medication. Its dosage strength can be gradually increased based on the severity of the condition. 

Erectile Dysfunction dosage guidelines-

  • One should not take Sildenafil tablets more than once to treat Erectile Dysfunction. 
  • Its use with children is not recommended. 
  • People over the age of 65 should start with 25mg of Sildenafil, whereas adults up to 65 years old can start with 50 mg. 

Treatment Of Pulmonary Arterial Hypertension (PAH)-

  • For PAH its dosage can be taken three times a day. 
  • The pediatric use of Sildenafil should be done only under medical supervision. 
  • Maintain a dosage gap of 4 to 6 hours. 

Sildenafil Dosage By Weight

Body Weight  Minimum Dosage  Sildenafil Max Dose
Weight 45kg or more 20 mg three times a day 80 mg three times a day in adults and 40 mg in children. 
20 to 45 kg 20 mg to be taken three times a day 40 mg. 
20 kg or less 20 mg to be taken three times a day 20 mg. 

How To Take Sildenafil

  • Sildenafil is an oral tablet that can be swallowed with water. 
  • The Sildenafil dosage can be taken with or without food. 
  • Do not break or crush the tablets before administering them. 
  • The best time to take sildenafil is about 30 minutes to 1 hour before intercourse. 

Sildenafil Reviews

Sildenafil reviews on WebMD show its average positive feedback as 3.9 out of 5 [2].
sildenafil review
Meanwhile, the Sildenafil user rating on Drugs is 8.3 out of 10 from a total review of 492, with 78% of users reporting a positive experience [4].

Condition  Average Rating On Drugs 
Erectile Dysfunction   8.3
Sexual Dysfunction, SSRI Induced (Off-label) 8.2
Pulmonary Arterial Hypertension   6.8

Sildenafil Interactions

Sildenafil can interact with 328 medications. It is known to cause 37 major, 287 moderate, and 4 minor drug interactions when administered with other medications. 

Some of the medications that should be taken with Sildenafil are listed below. 

Major Interactions Moderate Interactions
Amprenavir Butabarbital
Boceprevir Morphine
Clarithromycin Ciprofloxacin
Fosamprenavir Codeine
Ketoconazole Oxycodone
Riociguat Hydrocodone
Tadalafil Methadone
Voriconazole Nitric Oxide
Ritonavir St. John’s Wort
Erythromycin Rifampin

The four minor interactions of Sildenafil include Armodafinil, Modafinil, Dipyridamole, and Theophylline. 

Side Effects Of Sildenafil- Is Sildenafil Safe?

The most common side effects of sildenafil include dizziness, diarrhea, redness of the skin, runny nose, flushing, headache, and stomach upset. It may also cause vision changes such as blurry sight, increased sensitivity to light, and difficulty in telling apart between blue and green colors. 

If you experience a painful erection for 4 hours or more, it is important to consult a doctor immediately. 

In rare cases, it can cause anxiety, sudden weakness, confusion, bone pain, cold sweats, dry eyes and mouth, excessive hunger, trouble breathing, muscle twitching, nightmares, restless sleep, seizures, shakiness, and a sore throat. 

Long-Term Side Effects Of Sildenafil

The long-term use of Sildenafil is considered safe, with no notable signs of severe adverse effects. However, a 2003 study by Rupesh Raina et al. indicates that the most common side effects of Sildenafil after 3 years of use were headache,  blurred vision, and flushing [5]. 

Sildenafil Warnings

  • To ensure that the use of Sildenafil is a safe treatment option for you, discuss with your doctor if you have or have had a history of the following health conditions-
    • Heart disorders include chest pain, heart attack, or heart rhythm disorder. 
    • Bleeding problem. 
    • Low or high blood pressure.
    • Liver or kidney issues. 
    • Stomach ulcers.
    • Retinitis pigmentosa (an inherited condition of the eye).
    • Blood cell disorders such as leukemia,  sickle cell anemia, and multiple myeloma. 
    • An issue in the blood circulation. 
    • Any physical deformity of the penis, also known as Peyronie’s disease. 
  • It is not advisable for pregnant and lactating women to take Sildenafil for PAH without consulting a doctor. 
  • People below the age of 18 should not take this medication without medical advice. 
  • Do not take other PDE5 inhibitors, including Vardenafil (Levitra) and Tadalafil (Cialis)
  • Sildenafil tablets do not protect against sexually transmitted diseases, including HIV or AIDS. Thus, it is advisable to use protective measures. 

Dietary Restrictions-

  • The administration of Sildenafil tablets with high-fat meals may make the medication take longer to start working. 
  • The intake of grapefruit or grapefruit juice with Sildenafil must be done under the supervision of a physician. 
  • Avoid mixing sildenafil and alcohol together. 

Storage And Disposal Of The Sildenafil Tablets

  • Keep the medication away from pets and children’s reach. 
  • They must be kept at room temperature, away from direct sunlight and moisture. 
  • When disposing of expired or unnecessary tablets, it is advisable to either flush them down or wrap them in newspaper before throwing them in the trash can.  


How much Sildenafil is too much?

For erectile dysfunction, do not take Sildenafil tablets more than once. Whereas for pulmonary arterial hypertension (PAH), it can be taken three days a day. Taking a dose more than recommended can cause overdosing.

What is Viagra?

Viagra is the brand name of Sildenafil that was approved by the FDA in the USA in 1998. It is formulated with Sildenafil citrate as the active compound. It was after the expiry of the patent for Viagra that generic Sildenafil tablets became available in the market.

How long does Sildenafil last?

Sildenafil's action lasts for about 4 hours.

Does Sildenafil expire?

Yes, Sildenafil has a shelf life of 2 years.

How long does Sildenafil take to work?

It takes about 12 minutes to 30 minutes for Sildenafil to work.

How long does Sildenafil stay in your system?

Sildenafil can stay in the system for 20 to 24 hours.

Can women take Sildenafil?

Yes, women can take Sildenafil tablets for treating pulmonary arterial hypertension (PAH).

Does Sildenafil make you last longer?

The use of Sildenafil can help people with erectile dysfunction last longer.

Does Sildenafil make you bigger?

No, the use of Sildenafil will not change the size of the penis.

When to take Sildenafil?

Sildenafil should be taken 30 minutes to 1 hour before intercourse for people suffering from Erectile dysfunction. Whereas for treating pulmonary arterial hypertension (PAH) it can be administered 3 times a day.

What happens if you take expired Sildenafil?

Taking expired Sildenafil tablets is not advisable as it can increase the risk of experiencing side effects. Such medications may also be less effective due to the change in the chemical composition over time.

Is generic sildenafil as good as Viagra?

Yes, generic Sildenafil is as good as Viagra as they are composed of the same active compound.

How much is Sildenafil 100 mg at Walmart?

Thirty tablets of Sildenafil 100 mg is priced at $26 at Walmart.

Is Sildenafil covered by insurance?

Yes, the cost of Sildenafil is covered by most insurance companies.

How long can Sildenafil side effects last?

Most of the sildenafil side effects are temporary and may last for a few days to a few weeks. They often go away on their own once the body adjusts to the medication.

How long before sex should I take Sildenafil?

Take Sildenafil tablets 30 to 60 minutes before intercourse.

How often can you take Sildenafil?

For Erectile Dysfunction (ED), Sildenafil tablets can be taken once a day, whereas for pulmonary arterial hypertension (PAH), they can be taken thrice daily.

Does Sildenafil keep you hard after coming?

No, Sildenafil cannot keep you hard after ejaculating.


  1. Oral Sildenafil in the Treatment of Erectile Dysfunction, nejm. 
  2. Sildenafil, NCBI. 
  3. User Reviews for Sildenafil Oral, WebMD. 
  4. Sildenafil User Reviews & Ratings, drugs. 
  5. Long-term effect of sildenafil citrate on erectile dysfunction after radical prostatectomy: 3-year follow-up, PubMed. Protection Status
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