Sildenafil Citrate

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].

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.