Viagra – the Most Popular Erectile Dysfunction Medication

In a world where sexual performance is often synonymous with virility and masculinity, millions of men face debilitating effects of erectile dysfunction. Enter Viagra, the iconic blue pill that revolutionized of this common condition and has since become a household name. Originally developed as a cardiovascular medication, Viagra’s unexpected side effect quickly caught the attention of researchers and consumers alike. Today, it remains one of the most recognizable and widely used drugs in the world, offering hope and renewed intimacy to countless couples. Join us as we explore the history, efficiency, and impact of this groundbreaking medication, and discover how it continues to transform lives and relationships today.

Briefly about Viagra

Overview of Viagra

Viagra is a medication used to treat erectile dysfunction (ED), a condition in which a man has difficulty getting or maintaining an erection during sexual activity. The active ingredient in Viagra is sildenafil citrate, which belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. When a man is sexually stimulated, Viagra works by relaxing the blood vessels in the penis, allowing for increased blood flow and resulting in an erection.

History of Viagra

Viagra’s journey from a medication intended for hypertension and angina to a widely recognized treatment for erectile dysfunction is a fascinating story. When Pfizer first developed the drug in the early 1990s, it was known as sildenafil citrate and was intended to treat high blood pressure and angina, a type of chest pain. However, during clinical trials, researchers noticed an unexpected side effect: male participants were experiencing erections.

The discovery of this side effect prompted Pfizer to shift their focus and invest more resources into studying the potential of sildenafil citrate as a treatment for erectile dysfunction. In 1998, the US Food and Drug Administration (FDA) approved the drug under the brand name Viagra for the treatment of ED.

Viagra quickly became a commercial success, with sales reaching $1 billion in its first year on the market. The drug was not without controversy, however. Some critics argued that Viagra was overprescribed and that it reinforced unhealthy societal expectations around male sexual performance.

Despite these criticisms, Viagra has continued to be a widely prescribed medication for ED. In fact, it has paved the way for other drugs in the same class, such as Cialis and Levitra. Additionally, the development of Viagra and other PDE5 inhibitors has spurred research into the relationship between vascular health and sexual dysfunction, leading to new insights into the connection between ED and cardiovascular disease.

Importance of Viagra

Viagra has been a game-changer for men who struggle with ED, a condition that can have a significant impact on their quality of life and relationships. By providing a safe and effective treatment option, Viagra has helped many men regain their sexual function and confidence. It has also opened up conversations about sexual health and the importance of seeking medical treatment for ED.

Beyond its impact on individual patients, Viagra has also had a broader cultural and social impact. It has been the subject of numerous jokes and references in popular culture, and has played a role in discussions around masculinity, aging, and sexuality. Additionally, the development of Viagra and other PDE5 inhibitors has paved the way for research into other conditions that may be related to vascular health, such as heart disease and pulmonary hypertension.

How Viagra works

Role of Nitric Oxide in Viagra’s mechanism of action

Viagra works by blocking the action of an enzyme called phosphodiesterase type 5 (PDE5). This enzyme is responsible for breaking down cyclic guanosine monophosphate (cGMP), a chemical that plays a crucial role in regulating blood flow in the penis.  Nitric oxide plays a key role in Viagra’s mechanism of action. When a man is sexually stimulated, nitric oxide is released from nerve endings in the penis, which stimulates the production of cGMP. However, PDE5 breaks down cGMP, which can prevent an erection from occurring or cause it to be short-lived. By blocking the action of PDE5, Viagra allows cGMP to accumulate, which leads to increased blood flow and a longer-lasting erection.

Effects of Viagra on the body

Viagra’s effects on the body are primarily focused on the blood vessels in the penis. By increasing blood flow to the penis, Viagra can help men with ED achieve and maintain an erection. However, the drug can also have some other effects on the body, such as lowering blood pressure. This is because nitric oxide is also involved in regulating blood pressure, and blocking PDE5 can cause a slight decrease in blood pressure.

 Viagra also does not protect against sexually transmitted infections or pregnancy. Like all medications, Viagra can have side effects, such as headache, flushing, and dizziness. Additionally, it can interact with certain medications, such as nitrates, which are used to treat heart disease. It’s important to consult with a doctor before taking Viagra or any other medication for ED.

Is Viagra an aphrodisiac?

It’s important to note that Viagra is not an aphrodisiac and does not increase sexual desire. Viagra and aphrodisiacs differ in their mechanism of action and the way they affect sexual function. Viagra works by blocking the action of the enzyme PDE5, which can help achieve and maintain an erection.

Aphrodisiacs, on the other hand, are substances or activities that are believed to enhance sexual desire or pleasure. They may include foods, herbs, or supplements that are thought to have an arousing effect or enhance libido. However, there is limited scientific evidence to support the efficacy of aphrodisiacs, and their effects can vary widely from person to person.

Uses and Indication

1. Erectile Dysfunction (ED)

Erectile dysfunction (ED), also known as impotence, is a common condition that affects millions of men worldwide. It is defined as the inability to achieve or maintain an erection sufficient for sexual activity. ED can be caused by a variety of factors, including physical conditions such as diabetes, high blood pressure, or heart disease, as well as psychological factors such as anxiety or depression.

ED can also be a symptom of other underlying health issues, such as hormonal imbalances, nerve damage, or medication side effects. It is important for men who experience ED to talk to their doctor, as it can be a sign of a more serious health condition. As ED can be a difficult and embarrassing condition for men to discuss, it is important to seek medical attention. Treatment options for ED can vary depending on the underlying cause, but may include medications like Viagra, lifestyle changes such as exercise and diet modification, or psychotherapy.

2. Pulmonary Hypertension

Pulmonary hypertension is a type of high blood pressure that affects the arteries in the lungs and the right side of the heart. It occurs when the blood vessels in the lungs become narrow and stiff, making it difficult for the heart to pump blood through them. This can cause the heart to work harder than normal, leading to damage and eventually heart failure.

According to The New York Times, pulmonary hypertension can be caused by a variety of factors, including genetic factors, lung diseases, and heart diseases. It can also be a side effect of certain medications or recreational drugs. Symptoms of pulmonary hypertension can include shortness of breath, fatigue, chest pain, and swelling in the legs and ankles.

Treatment options for pulmonary hypertension can vary depending on the underlying cause and severity of the condition. Viagra works by relaxing the blood vessels in the lungs, which can improve blood flow and reduce blood pressure. It is often used in combination with other medications for the treatment of pulmonary hypertension.

3. Raynaud’s Phenomenon

Another less common use of Viagra is for the treatment of Raynaud’s phenomenon, a condition that affects the blood vessels in the fingers and toes. When exposed to cold temperatures or stress, the blood vessels in these areas can constrict, leading to a decrease in blood flow and oxygen to the tissues. This can cause a range of symptoms, including numbness, tingling, pain, and even skin discoloration.

While there is no cure for Raynaud’s phenomenon, there are treatment options available to manage symptoms. It is typically prescribed as a second-line treatment for patients who do not respond to other therapies. By increasing blood flow to the affected areas, Viagra can alleviate symptoms and improve quality of life for those with Raynaud’s.

It is important to note that while Viagra can be effective for managing symptoms of Raynaud’s, it is not a first-line treatment and should only be used under the guidance of a healthcare professional.

4. Other potential uses of Viagra

Research is ongoing into the potential uses of Viagra for other medical conditions, such as diabetes-related nerve damage and altitude sickness. However, these potential uses are not yet approved by regulatory agencies and require further study. It is important to note that Viagra should only be taken under the supervision of a healthcare professional and for its approved indications. Misuse or abuse of the drug can have serious health consequences.

Dosage forms of Viagra

Dosage recommendations for various indications

Viagra is available in several dosage forms, including:

• tablets,
• oral suspension, and
• injectable solution.

The tablet form is the most commonly prescribed, with dosages ranging from 25 mg to 100 mg. The dosage will depend on the patient’s age, health condition, and other factors.

Viagra Forms and Dosages:

Form	Dosage
Tablet	25mg, 50mg, 100mg
Oral jelly	100mg
Chewable tablet	50mg
Sublingual tablet	25mg, 50mg
Buccal tablet	100mg

The recommended dosage of Viagra for erectile dysfunction is typically 50 mg, taken 30 minutes to one hour before sexual activity. The dosage can be adjusted up or down based on the patient’s response and any side effects. For pulmonary hypertension, the recommended dosage of Viagra is typically 20 mg three times a day.

When do you need oral suspension or injectable solution of Viagra?

There may be situations where an oral suspension or injectable solution of Viagra is necessary or preferred.

Oral suspension: An oral suspension may be necessary for individuals who have difficulty swallowing tablets or pills, such as those who have had a stroke or have a condition that affects their ability to swallow. In some cases, an oral suspension may also be prescribed for those who require a smaller dose.

Injectable solution: An injectable solution of Viagra may be used in certain medical situations, such as when an individual is unable to take medication by mouth due to nausea or vomiting, or when a rapid onset of action is required. The injectable solution of Viagra is administered by a healthcare professional and is typically used in a hospital or clinical setting.

It’s important to note that the use of an oral suspension or injectable solution of Viagra should only be done under the guidance and supervision of a healthcare professional, as there are potential risks and side effects associated with the use of this medication in any form.

Administration of Viagra

Viagra is typically administered orally, with the tablet taken with a glass of water. The medication can be taken with or without food, although it may take longer to work if taken with a high-fat meal. You should avoide alcohol while taking Viagra, as it can increase the risk of side effects and reduce the medication’s effectiveness.

It is important to follow the dosage recommendations provided by a healthcare professional, as taking too much Viagra can increase the risk of side effects. Additionally, Viagra should not be taken with certain medications or medical conditions, so it is important to inform your doctor of any other medications you are taking.

Interactions and Contraindications

Drug interactions with Viagra

While taking viagra, it is important to be aware of potential drug interactions when taking Viagra as they can increase the risk of adverse effects or decrease its effectiveness.

Firstly, Viagra should not be taken in combination with nitrates such as nitroglycerin or isosorbide dinitrate. Nitrates are commonly used to treat angina and other heart conditions, and combining them with Viagra can lead to a dangerous drop in blood pressure, causing dizziness, fainting, or even a heart attack. Additionally, some medications used to treat HIV, such as ritonavir and saquinavir, can increase the amount of Viagra in the bloodstream, leading to an increased risk of side effects. Other medications that may interact with Viagra include alpha-blockers, blood thinners, and certain antibiotics. It is important to inform your healthcare provider of all medications you are taking before starting Viagra to avoid potential drug interactions.

Precautions and Warnings for use of Viagra

While it is generally considered safe and effective when used as directed, there are some precautions and warnings that should be considered before using this medication. Some of these include:

1. Do not use with certain medications: Viagra should not be used with medications containing nitrates, such as nitroglycerin, as this can cause a dangerous drop in blood pressure. It is also not recommended to use Viagra with alpha-blockers, such as doxazosin, as this can increase the risk of low blood pressure.
2. Do not use with certain medical conditions: Individuals with certain medical conditions, such as severe liver or kidney disease, should not use Viagra. Additionally, those who have experienced a recent heart attack or stroke, or have unstable angina, should not use Viagra.
3. Use with caution in certain populations: Older individuals or those with pre-existing cardiovascular disease may be more susceptible to the side effects of Viagra. Caution should also be taken when using Viagra in those with low blood pressure, a history of priapism (prolonged erections), or those with retinitis pigmentosa, a rare genetic eye disorder.
4. Proper dosing and use: Viagra should be taken as directed by a healthcare professional and should not be taken more frequently or at higher doses than recommended. It should also be noted that Viagra does not protect against sexually transmitted infections, including HIV.

Adverse Effects

Taking high doses of Viagra can lead to an increased risk of side effects, some of which can be serious. Taking too much Viagra can have negative consequences.

Common side effects of Viagra

Some common side effects of Viagra (sildenafil) include:

• Headache
• Flushing
• Indigestion
• Nasal congestion.

It’s important to note that while the common side effects of Viagra are generally mild and go away on their own.

Serious Adverse Effects of Viagra

High dose of Viagra may imply serious adverse effects such as:

• Cardiovascular effects, especially when taken with other blood pressure-lowering medications or nitrates (low blood pressure, dizziness, lightheadedness, fainting, heart attack)
• Vision and hearing loss, especially in those with a history of certain eye conditions or hearing problems or those taking medications that affect blood vessels
• Priapism (painful, prolonged erection lasting longer than 4 hours)

If you experience any of these symptoms after taking Viagra, it’s important to seek immediate medical attention. Anaphylaxis can be life-threatening if not treated promptly.

It’s also important to note that if you have a history of allergies or have had a previous allergic reaction to Viagra or any of its ingredients, you should not take Viagra. Be sure to talk to your healthcare provider about any allergies you may have before starting treatment with Viagra or any other medication.

If you experience any other unusual symptoms or side effects while taking Viagra, it’s important to notify your healthcare provider right away. They can help determine whether the symptoms are related to the medication and whether any changes to your treatment plan are needed.

Risks and Benefits of using Viagra

Like any medication, using Viagra carries some risks and benefits. The benefits of using Viagra include treating erectile dysfunction and improving sexual function. However, it is important to consider the potential risks of using the medication. Some individuals may experience side effects, and there may be risks associated with using Viagra in individuals with certain medical conditions, such as severe liver or kidney disease or a history of heart attack or stroke. Before using Viagra, it is important to speak with a healthcare professional to determine if the benefits outweigh the risks.

Interactions and Contraindications

Viagra can interact with certain medications and substances, including nitrates (often used to treat chest pain or angina), alpha-blockers (used to treat high blood pressure or prostate enlargement), and grapefruit juice. These interactions can increase the risk of side effects or decrease the effectiveness of the medication. Additionally, individuals with certain medical conditions, such as severe liver or kidney disease, should not use Viagra. It is important to speak with a healthcare professional to determine if Viagra is safe and appropriate for you, and to discuss any potential interactions or contraindications.

Alternatives to Viagra

Other treatments for erectile dysfunction

There are a number of methods to help manage ED. All of them are aimed at eliminating the underlying causes of the disease, regardless of whether they are physical or psychological in nature.

Lifestyle changes	Making lifestyle changes such as exercising regularly, quitting smoking, reducing alcohol consumption, and maintaining a healthy weight can improve blood flow to the penis, which is essential for achieving and maintaining an erection. By improving overall health and reducing risk factors for cardiovascular disease, these lifestyle changes can also help reduce the severity of ED symptoms.
Psychotherapy	ED can have psychological causes, such as anxiety, depression, or relationship issues. Psychotherapy, including cognitive-behavioral therapy or sex therapy, can help address these underlying psychological factors, which can contribute to ED.
Oral medications	Viagra (sildenafil) and other oral medications like tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra) are all in the same category of phosphodiesterase type 5 (PDE5) inhibitors. These drugs work by relaxing the smooth muscles in the blood vessels in the penis, which increases blood flow and helps men achieve and maintain an erection. They are commonly used to treat ED and have been shown to be effective in many cases.

Other treatments for pulmonary hypertension

Viagra (sildenafil) is also used to treat pulmonary hypertension (PH), a condition in which high blood pressure occurs in the lungs. Other medications used to treat PH include:

1. Endothelin receptor antagonists: Bosentan (Tracleer) and ambrisentan (Letairis) are medications that can help improve PH symptoms by blocking the effects of endothelin, a substance that can narrow blood vessels in the lungs.
2. Prostacyclin analogs: Epoprostenol (Flolan), treprostinil (Remodulin), and iloprost (Ventavis) are medications that mimic the effects of prostacyclin, a substance that can help dilate blood vessels in the lungs.
3. Phosphodiesterase type 5 inhibitors: Tadalafil (Adcirca) and sildenafil (Revatio) are medications that can help improve blood flow in the lungs.

Non-pharmacological alternatives to Viagra

There are several non-pharmacological alternatives to Viagra for treating erectile dysfunction (ED), including:

Vacuum devices	A vacuum device, also known as a penis pump, is a non-invasive treatment that can help men with erectile dysfunction achieve an erection. The device is placed over the penis and creates a vacuum, which draws blood into the penis, causing an erection. The erection is then maintained by placing a ring at the base of the penis to trap the blood. Vacuum devices are generally safe and have few side effects, although some men may experience discomfort or bruising.
Penile injections or suppositories	Alprostadil is a medication that can be administered via injection or suppository to improve blood flow to the penis and help men achieve an erection. The medication works by relaxing the smooth muscles in the blood vessels, which allows for increased blood flow to the penis. Penile injections and suppositories are typically reserved for men who have not responded to other treatments, as they can be more invasive and have more potential side effects, such as pain or prolonged erections.
Acupuncture	Acupuncture is an ancient Chinese therapy that involves inserting thin needles into specific points on the body to balance energy flow and promote healing. Some studies have suggested that acupuncture may be effective in improving ED symptoms, although more research is needed to fully understand its effectiveness. Acupuncture is generally considered safe, although some men may experience discomfort or bleeding at the needle insertion sites. It is important to find a licensed and experienced acupuncturist to perform the treatment.

It is important to speak with a healthcare professional to determine the most appropriate treatment options, as well as to discuss any potential risks or side effects associated with non-pharmacological alternatives to Viagra.

Controversies and Myths

Controversies surrounding Viagra

1. Increased risk of melanoma: Some studies have suggested that men who use Viagra may be at an increased risk of developing melanoma, a type of skin cancer. However, other studies have not found a significant association between Viagra use and melanoma risk. The current evidence is inconclusive, and more research is needed to determine whether Viagra use is a risk factor for melanoma.
2. Recreational use: Viagra has become a popular recreational drug among some men, who use it to enhance sexual performance even if they do not have erectile dysfunction. However, using Viagra without a medical need can be dangerous, as it can lead to serious side effects and interactions with other medications.
3. Counterfeit products: Due to the high demand for Viagra, counterfeit versions of the drug are sometimes sold online or in other unregulated markets. These products may not contain the active ingredient in Viagra or may contain dangerous contaminants, which can be harmful to health.

Myths and misconceptions about Viagra

Viagra is an aphrodisiac

Viagra is not an aphrodisiac and does not increase sexual desire on its own, as we’ve discussed above. It only works when there is sexual stimulation, and it does not create sexual desire where there is none.

Viagra increases penis size

Another common myth about Viagra is that it increases penis size. However, Viagra does not actually increase the size of the penis. It works by increasing blood flow to the penis, which can result in a firmer and longer-lasting erection, but it does not physically increase the size of the penis. It is important to have realistic expectations when taking Viagra and to understand that it is not a solution for penis enlargement.

Viagra is addictive

Viagra is not addictive, and it does not create a physical dependency on the drug. However, some men may become psychologically dependent on Viagra, especially if they have anxiety about their sexual performance.

Viagra causes permanent erection

Viagra does not cause a permanent erection, and it does not change the structure of the penis. However, taking too much Viagra can lead to priapism, a painful and prolonged erection that requires emergency medical attention.

Is Viagra Safe?

Studies have consistently shown that Viagra is a safe and effective medication for the treatment of erectile dysfunction. The safety and efficacy of Viagra have been established through numerous clinical trials and real-world use by millions of men worldwide.

In clinical trials, Viagra has been shown to significantly improve erectile function in men with varying degrees of erectile dysfunction. A systematic review and meta-analysis of randomized controlled trials found that Viagra was more effective than placebo in improving erectile function, with a success rate of 60-70% in achieving erections sufficient for sexual intercourse.

Moreover, long-term safety data of Viagra from clinical trials and post-marketing surveillance have shown that the medication is generally well-tolerated and does not increase the risk of serious adverse events. The most common side effects of Viagra are mild and temporary, such as headache, flushing, and indigestion, and usually go away on their own.

Future of Viagra

Current research on Viagra

Research on Viagra (sildenafil citrate) is ongoing and focuses on various aspects of the medication, including its effectiveness, safety, and potential applications beyond erectile dysfunction. Some current areas of research on Viagra include:

1. Treatment of pulmonary arterial hypertension (PAH): PAH is a type of high blood pressure that affects the arteries in the lungs and can lead to heart failure. Viagra has been approved for the treatment of PAH in some countries and is currently being studied in clinical trials to determine its effectiveness and safety.
2. Treatment of Raynaud’s phenomenon: Raynaud’s phenomenon is a condition that causes the blood vessels in the fingers and toes to narrow, resulting in pain, numbness, and tingling. Viagra has been shown to improve blood flow in people with Raynaud’s phenomenon and is being studied as a potential treatment.
3. Treatment of female sexual dysfunction: Viagra has been studied as a potential treatment for female sexual dysfunction, which includes disorders such as hypoactive sexual desire disorder and female sexual arousal disorder. While the results of these studies have been mixed, some women have reported improved sexual function with the use of Viagra.

Potential future uses of Viagra

In addition to the current applications of Viagra, there are several potential future uses that are being explored. Some of these include:

1. Treatment of heart failure: Heart failure is a condition in which the heart is unable to pump enough blood to meet the body’s needs. Viagra has been shown to improve heart function in animal studies and is being studied as a potential treatment for heart failure in humans.
2. Treatment of cancer: Viagra has been shown to have anti-cancer effects in some preclinical studies, and is being studied as a potential treatment for various types of cancer, including prostate cancer and colorectal cancer.
3. Treatment of altitude sickness: Altitude sickness is a condition that can occur when people travel to high altitudes and experience a decrease in the amount of oxygen available. Viagra has been shown to improve oxygen delivery to the body and is being studied as a potential treatment for altitude sickness.

New formulations and delivery methods for Viagra

Researchers are developing new dosage forms and delivery methods for Viagra (sildenafil citrate) to improve efficacy, safety and convenience. In particular, today we can talk about the following new forms and delivery methods that are currently being studied:

1. Sublingual tablets: Sublingual tablets are placed under the tongue and dissolve quickly, allowing the medication to enter the bloodstream more rapidly than oral tablets. Studies have shown that sublingual sildenafil may have a faster onset of action and produce more consistent results than oral sildenafil.
2. Orally disintegrating tablets: Orally disintegrating tablets are designed to dissolve quickly in the mouth without the need for water. This can be particularly useful for people who have difficulty swallowing tablets.
3. Topical creams and gels: Topical creams and gels containing sildenafil are being studied as a potential treatment for erectile dysfunction. These products are applied directly to the penis and may produce fewer side effects than oral medications.
4. Intranasal delivery: Intranasal delivery involves administering the medication through the nasal passages. Studies have shown that intranasal sildenafil may have a faster onset of action and produce more consistent results than oral sildenafil.
5. Transdermal patches: Transdermal patches containing sildenafil are being studied as a potential treatment for erectile dysfunction. These patches are applied to the skin and deliver the medication through the skin and into the bloodstream.
6. Long-acting formulations: Long-acting formulations of sildenafil are being developed to provide sustained release of the medication over a longer period of time. This could potentially improve the effectiveness and convenience of the medication.

Conlusion

Let’s highlight the key points of Viagra.

Viagra, also known as sildenafil citrate, is a medication that has helped millions of men worldwide to treat their erectile dysfunction. By increasing blood flow to the penis, Viagra enables men to achieve and maintain an erection, leading to improved sexual performance and satisfaction.

Viagra has had a significant positive impact on the quality of life for men with erectile dysfunction. By improving sexual function and satisfaction, Viagra can boost self-esteem and restore confidence in intimate relationships. Studies have shown that men who take Viagra report improved sexual activity and overall satisfaction with their sex life.

In addition to the physical benefits, Viagra can also have a positive impact on mental health and well-being. Erectile dysfunction can lead to feelings of embarrassment, anxiety, and depression, which can affect a man’s overall quality of life. By treating erectile dysfunction, Viagra can alleviate these psychological symptoms and improve a man’s overall sense of well-being.

But please remember that while it can cause some side effects, such as headaches, redness, and nasal congestion. However, these side effects are usually mild and go away on their own.

Moving on to the future of Viagra, researchers are currently exploring new formulations and delivery methods to improve the effectiveness, safety, and convenience of the medication. These include sublingual tablets, orally disintegrating tablets, topical creams and gels, intranasal delivery, transdermal patches, and long-acting formulations.

Final thoughts on Viagra’s impact on healthcare and society

Overall, Viagra has had a significant impact on healthcare and society by providing an effective treatment option for men with erectile dysfunction. It has also sparked discussions and debates about sexuality, masculinity, and aging. While there are still some controversies surrounding the use of Viagra, it has undoubtedly helped many men and their partners to improve their quality of life and intimacy.

Sources:

• National Institutes of Health. (2021). Sildenafil. https://livertox.nlm.nih.gov/Sildenafil.htm
• Chrysant, S. G. (2018). The Current and Future Role of Sildenafil in the Treatment of Cardiovascular Diseases. American Journal of Cardiovascular Drugs, 18(5), 325-334. https://doi.org/10.1007/s40256-018-0267-6
• Zhang, H., Xu, Y., Wei, J., Xie, C., Cao, Y., Dong, D., & Wang, Y. (2022). Sildenafil: Current status and future perspectives for cancer treatment. Cancer Letters, 523, 1-8. https://doi.org/10.1016/j.canlet.2021.10.017
• Bärtsch, P., Mairbäurl, H., & Swenson, E. R. (2013). Sildenafil and tadalafil for the treatment of severe high altitude pulmonary edema. High Altitude Medicine & Biology, 14(3), 253-259. https://doi.org/10.1089/ham.2013.1024

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