2 DOSAGE AND ADMINISTRATION

Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection.

How should this medicine be used?

While sildenafil improves some markers of disease in people with pulmonary arterial hypertension, it does not appear to affect the risk of death or serious side effects. Sildenafil and other PDE5 inhibitors are used off-label to alleviate vasospasm and treat severe ischemia and ulcers in fingers and toes for people with secondary Raynaud's phenomenon;[9][21] these drugs have moderate efficacy for reducing the frequency and duration of vasospastic episodes. [9] As of 2016,[update] their role more generally in Raynaud's was not clear. Sildenafil has shown some potential for improving exercise performance at high altitudes. However, its overall efficacy is not clear.

Common Side Effects

Sildenafil has been studied for high-altitude pulmonary edema (HAPE), but its use is currently not recommended for that indication. In clinical trials, the most common adverse effects of sildenafil use included headache, flushing, indigestion, nasal congestion, and impaired vision, including photophobia and blurred vision. [4] Some sildenafil users have complained of seeing everything tinted blue (cyanopsia). [24] This cyanopsia can be explained because sildenafil, while selective for PDE5, does have some affinity for PDE6, which is the phosphodiesterase found in the retina. Patients thus taking the drug may sildenafil pills experience colorvision abnormalities. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects.

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Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours.

• Common side effects include headache and flushing.
• Some may experience nasal congestion or dizziness.
• Serious side effects require immediate medical attention.

[4] Other drugs that interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels.

Advice To Patients

If you are taking sildenafil (Liqrev, Revatio) for PAH, do not stop taking your medication until you talk to your doctor. Call your doctor if you have any unusual problems while you are taking this medication. If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088). Keep this medication in the container it came in, tightly closed, and out of reach of children. Store the tablets at room temperature and away from excess heat and moisture (not in the bathroom).

Storage Requirements

Store the suspension at room temperature or in a refrigerator, but do not freeze it. Dispose of any unused suspension after 60 days. Keep all medication out of sight and reach of children as many containers are not child-resistant. Place the medication in a safe sildenafil oral solution location – one that is up and away and out of their sight and reach. Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. The use of sildenafil and an α1 blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart.

Common Side Effect	Frequency	Severity	Notes
Headache	Very common	Mild to moderate	Usually transient
Flushing	Common	Mild	Often resolves quickly
Dyspepsia / Indigestion	Common	Mild	Can be managed with antacids
Visual Disturbances	Less common	Mild	Changes in color perception
Priapism	Rare	Serious	Medical emergency, requires immediate attention

Concomitant use of nitric oxide donors, organic nitrites and nitrates,[30] such

What is sildenafil?

Some complained of blurriness and loss of peripheral vision. In July 2005, the US Food and Drug Administration (FDA) updated labeling for tadalafil (Cialis), vardenafil (Levitra), and sildenafil (Viagra) to reflect a small number of post-marketing reports of sudden vision loss, while acknowledging that "...it is not possible to determine whether these oral medicines for erectile dysfunction were the cause of the loss of eyesight or whether the problem is related to other factors such as high blood pressure or diabetes, or to a combination of these problems. "[25] A careful review of pooled data from clinical trials containing well documented information about the dose and duration of exposure to the drug for a large number of patients, yields no evidence for an increased risk of non-arteritic anterior ischemic optic neuropathy or other adverse ocular events associated with PDE5 inhibitor use. Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. [4] In October 2007, the FDA announced that the labeling for all PDE5 inhibitors, including sildenafil, required a more prominent warning of the potential risk of sudden hearing loss. as: nitroglycerinisosorbide mononitrateisosorbide dinitratesodium nitroprussidealkyl nitrites (commonly known as "poppers") Concomitant use

• Sildenafil is generally safe when used as prescribed.
• Always follow your healthcare provider’s dosage instructions.
• Do not double doses if a dose is missed.

of soluble guanylyl cyclase stimulators, such as riociguat Sildenafil should not be used if sexual activity is inadvisable due to underlying cardiovascular risk factors.

5.6 Adverse Reactions with the Concomitant Use of Ritonavir

Sildenafil, sold under the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. [4][8] It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud's phenomenon. [9] It is unclear if it is effective for treating sexual dysfunction in females. [8] It can be taken orally (swallowed by mouth), intravenously (injection into a vein), or through the sublingual route (dissolved under the tongue). [8][10] Onset when taken orally is typically within twenty minutes and lasts for about two hours.

How should Sildenafil Citrate Tablets be stored?

Common side effects include headaches, heartburn, and flushed skin. [8] Caution is advised in those with cardiovascular disease. [8] Rare but serious side effects include vision problems, hearing loss, and prolonged erection (priapism) that can lead to damage to the penis. [8] Sildenafil should not be taken by people on nitric oxide donors such as nitroglycerin, as this may result in a serious drop in blood pressure. Sildenafil acts by blocking phosphodiesterase 5 (PDE5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis. Sildenafil's popularity with young adults has increased over the years.

• Sildenafil citrate is used to treat erectile dysfunction.
• It enhances blood flow to the penis for a stronger erection.
• Commonly available in tablet form for oral use.

[32] Sildenafil's brand name, Viagra, is widely recognized in popular culture, and the drug's association with treating erectile dysfunction has led to its recreational use.

Viagra (Sildenafil) – Proven Support for Erectile Dysfunction

[8] It requires sexual arousal to work, and does not by itself cause or increase sexual arousal. [8] It also results in dilation of the blood vessels in the lungs. Pfizer originally discovered the medication in 1989 while looking for a treatment for angina. [11] It was buy sildenafil citrate online canada approved for medical use in the United States and in the European Union in 1998. [5][8][11][12] In 2023, it was the 151st most commonly prescribed medication in the United States, with more than 3 million prescriptions.

Revatio Tablets

[13][14] It is available as a generic medication. [15][16] In the United Kingdom, it is available as a pharmacy medicine. The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Its use is now one of the standard treatments for erectile dysfunction, including for males with diabetes mellitus. Tentative evidence suggests that sildenafil may help males who experience antidepressant-induced erectile dysfunction. [33] The reasons behind such use include the belief that the drug increases libido, improves sexual performance,[33] or permanently increases penis size.

• Overdose symptoms may include dizziness, nausea, or prolonged erections.
• Seek emergency help if an erection lasts over 4 hours.
• Avoid excessive dosing to prevent adverse events.

[34] Studies on the effects of sildenafil when used recreationally are limited, but suggest it has little effect when used by those who do not have erectile dysfunction.

5.4 Hearing Loss

Do not flush this medication down the toilet. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website for more information. In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Drugs Affecting or Metabolized by Hepatic Microsomal Enzymes

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription. Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies. In one study, a 25 mg dose was shown to cause no significant change in erectile quality, but did reduce the postejaculatory refractory time.

5.5 Hypotension when Co-administered with Alpha-blockers or Anti-hypertensives

If you experience a sudden loss of vision while you are taking sildenafil, call your doctor immediately. Do not take any more doses of sildenafil or similar medications such as tadalafil (Cialis) or vardenafil (Levitra) until you talk to your doctor. There have been reports of heart attack, stroke, irregular heartbeat, bleeding in the brain or lungs, high blood pressure, and sudden death in men who took sildenafil for erectile dysfunction. Most, but not all, of these people had heart problems before taking sildenafil. It is not known whether these events were caused by sildenafil, sexual activity, heart disease, or a combination of these and other causes.

Allergy warning

Talk to your doctor about the risks of taking sildenafil. Some patients experienced a sudden decrease or loss of hearing after they took sildenafil or other medications that are similar to sildenafil. It is not known if the hearing loss was caused by the medication. If you experience a sudden loss of hearing, sometimes with ringing in the ears or dizziness, while you are taking sildenafil, call your doctor immediately. If you are taking sildenafil (Viagra) for erectile dysfunction, do not take any more doses of sildenafil (Viagra) or similar medications such as tadalafil (Cialis) or vardenafil (Levitra) until you talk to your doctor. [35] This study also noted a significant placebo effect in the control group.

Property	Description	Value	Notes
Molecular Formula	C22H30N6O4S
Molecular Weight	474.58 g/mol
Melting Point	189-192°C
Solubility in Water	Slightly soluble		at 25°C
pH Range	3.8 - 4.0		in aqueous solution