Viagra's Mechanism for Pulmonary Hypertension

N Engl J Med 1992;326:90-94 Andersson, K-E, Wagner, G. Physiology of penile erection. The role of nitric oxide in the physiology of erection.

Property	Description	Units / Format	Notes
Active Ingredient	Sildenafil Citrate	mg	50 mg, 100 mg
Brand Names	Viagra, Revatio, Sildenafil	N/A	Variations depending on use
Typical Dosage	50-100 mg	mg	Taken as needed before sexual activity
Onset of Action	30-60 minutes	minutes	Time to start feeling effects
Duration of Effect	Up to 4-6 hours	hours	Effect duration

Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction.

• Viagra is considered a first-line treatment for erectile dysfunction.
• Its discovery was a breakthrough in sexual medicine.
• The drug’s molecular design targets specific enzymes to enhance blood flow.
• Viagra can sometimes cause dizziness or temporary vision loss.
• It was initially studied as a potential treatment for angina.
• Men taking Viagra often report improved confidence and intimacy.
• Sildenafil, the active compound, is now used in other medications.
• Higher doses do not necessarily mean better results and can increase side effects.

Sildenafil, a novel effective oral therapy for male erectile dysfunction.

• Viagra works by increasing blood flow to the penis during arousal.
• It is available in doses of 25 mg, 50 mg, and 100 mg tablets.
• Viagra is generally safe for most men when used as directed.
• It is not an aphrodisiac and requires sexual stimulation to work.
• The medication has revolutionized the treatment of erectile dysfunction.
• Viagra is often used off-label for pulmonary hypertension treatment.
• Age, health, and other medications can affect Viagra’s effectiveness.
• Improper use can cause low blood pressure or vision problems.

Br J Urol 1996;78:257-261 Rosen, RC, Riley, A, Wagner, G, Osterloh, IH, Kirkpatrick, J, Mishra, A.

What side effects can this medication cause?

The men we studied had a normal level of sexual desire, as might be expected of men with erectile dysfunction who enter a clinical trial,13 and sildenafil did not alter that level. Successful sexual intercourse was therefore a key end point for these men. Overall, the results of the efficacy assessments demonstrated that sildenafil significantly improved erectile function and quadrupled the success of intercourse, with effectiveness maintained for at least six months. Its main adverse effects were headache, flushing, dyspepsia, and visual disturbances and were usually mild. Only one man with a visual disturbance discontinued treatment, and he also had flushing.

Can I take Viagra after I’ve had my prostate removed?

Few men discontinued sildenafil, suggesting a relatively high level of drug tolerability and acceptance. No man had priapism after sildenafil treatment. Sildenafil has modest vasodilator properties but no effect on heart rate. The American Urological Association Panel on the Treatment of Organic Erectile Dysfunction stated that the ultimate goal is a therapy that is reliable, has minimal side effects, and is simple to use.6 Sildenafil appears to meet these specifications. Oral therapy permits discreet administration and is less invasive than some other treatment options, including injections into the corpus cavernosum, transurethral drug delivery, and prosthesis implantation. The International Index of Erectile Function (IIEF): a multidimensional scale for assessment of erectile dysfunction. Riley, AJ, Athanasiadis, L. Impotence and its non-surgical management. Br J Clin Pract 1997;51:99-103 Any commercial reuse of NEJM Group content requires permission. From the Department of Urology, Boston University Medical Center, Boston (I.G.

• Viagra was originally researched to treat cardiovascular diseases.
• The medication may cause temporary loss of blue-tinted vision.
• Sildenafil is used in both brand-name Viagra and generics.
• The drug’s impact on blood vessels was a significant scientific breakthrough.
• Side effects often subside within a few hours of intake.
• Viagra’s popularity spurred further research in sexual medicine.
• Men should watch for symptoms like chest pain or sudden vision changes.
• Consulting a healthcare provider ensures personalized and safe treatment.

); the Department of Urology, University of California, San Francisco (T.F.L.

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); the Department of Urology, University of Southern California, Los Angeles, and the Male Clinic, Santa Monica, Calif.

How should I take Viagra?

Sex-ual behavior in the human male. Efficacy and safety of intracavernosal alprostadil in men with erectile dysfunction. Treatment of men with erectile dysfunction with transurethral alprostadil. Clinical Guidelines Panel on Erectile Dysfunction: summary report on the treatment of organic erectile dysfunction. Nitric oxide as a mediator of relaxation of the corpus cavernosum in response to nonadrenergic, noncholinergic neurotransmission. (H.P.-N.); the Department of Psychiatry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, N.J. ); the Department of Urology, University of Virginia, Charlottesville (W.D.S. Select the format you want to export the citation of this publication.

What other drugs will affect Viagra?

Govier, Seattle; L. Hoffman, Gurnee, Ill.; J.M. Kaufman, Aurora, Colo.; I. Klimberg, Ocala, Fla.; V. Longo, New London, Conn.; T.

Less common

Malloy, Philadelphia; A. McCullough, New York; J. McMurray, Huntsville, Ala.; D.F. ; J Susset, Providence, R.I.; J. Tuttle, Lexington, Ky.; G. Multi-view semi-supervised adversarial attention network for drug repurposing, Computer Methods and Programs in Biomedicine, 282, (109406), (2026).

What other information should I know?

We found that sildenafil improves sexual function in men with erectile dysfunction. In keeping with sildenafil's mode of action (i.e., the drug causes erection only in response to sexual stimulation), the studies were performed entirely in a natural environment, which meant that we had to rely on the men's own reports of efficacy. However, the self-administered International Index of Erectile Function has a high degree of sensitivity and specificity for detecting treatment-related changes in men with erectile dysfunction.13 This questionnaire, together with the global-efficacy question, provided a comprehensive assessment of erectile function during a specified recall period (four weeks), and the event log provided information about individual events during treatment. The men's partners were questioned in each of the studies, and although the results corroborated the men's efficacy assessments, only 25 percent of the partners completed the optional questionnaire. Recognizing the fact that in most men erectile dysfunction is a multifactorial problem, we enrolled men with a broad variety of causes of erectile dysfunction.

How Supplied

The identification of an organic abnormality does not establish it as the cause of erectile dysfunction.14 Conversely, failure to identify an organic cause does not prove a psychogenic origin. In the dose–response study, increasing doses of sildenafil (25 to 100 mg) were increasingly effective in improving the frequency of penetration and the maintenance of erections after penetration, the mean score for the erectile-function domain of the International Index, and the percentage of men reporting better erections. In the dose-escalation study, sildenafil treatment was associated with improvements in the frequency of penetration and the maintenance of erections after penetration. The therapeutic response to sildenafil was similar in men with various causes of erectile dysfunction. The mean scores after sildenafil therapy approached those of normal men of the same age. Multi‐Target Mechanisms of Moroccan Aphrodisiac Plants: An Integrative Computational and Phytochemical Investigation, Food Science & Nutrition, 14, 5, (2026). Artificial intelligence in drug research and development: a review of methods and applications in drug repurposing, Briefings in Bioinformatics, 27, 3, (2026). Endocrine-metabolic crosstalk in erectile dysfunction: mechanistic insights and therapeutic implications, International Journal of Impotence Research, (2026). Therapeutic applications of phosphodiesterase inhibitors in male reproductive health: narrative review, Sexual Medicine Reviews, 14, 2, (2026). Oral suspension versus tablet sildenafil for erectile dysfunction: a prospective multicenter comparative study on patient satisfaction, International Journal of Impotence Research, (2026).

Condition / Situation	Reason	Recommendation
Use with Nitrates	Risk of severe hypotension	Avoid concomitant use
Cardiovascular conditions	Increased heart attack risk	Consult doctor before use
Recent stroke or unstable angina	Potential for worsening condition	Avoid until stabilized
Liver or kidney impairment	Altered drug metabolism	Dose adjustment necessary
Allergies to sildenafil or excipients	Risk of allergic reactions	Check ingredients carefully

Low‐intensity shockwave therapy for erectile dysfunction: An abridged Cochrane review, BJU International, 137, 6, (949-957), (2026).

2. Timing matters.

Burnett, Baltimore; R. Castellanos, Fort Myers, Fla.; L. Charles, Stratford, N.J.; F. Eid, New York; R. Feldman, Waterbury, Conn.; W.

Pulmonary Arterial Hypertension

Fitch III, San Antonio, Tex. ; T. Garland, Lawrence, N.J.; M. Gittelman, North Miami, Fla.; D. Gleason, Tucson, Ariz.; F. Current state of the problem, Andrology and Genital Surgery, 25, 4, (33-40), (2026).

2. How does Viagra work?

Wells, Birmingham, Ala.; C. White, Mobile, Ala.; J. Young, Laguna strongest viagra pill Hills, Calif.; and N. Zinner, Torrance, Calif. Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. Emerging Trends and Research Focus in Erectile Dysfunction Treatment: A 1993–2023 Bibliometric Analysis, Andrologia, 2026, 1, (2026). VIAGRA- sildenafil citrate tablet, film coated Pfizer Laboratories Div Pfizer Inc For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. However, VIAGRA may be taken anywhere from 30 minutes to 4 hours before sexual activity. The maximum recommended dosing frequency is once per day.

• Viagra is a prescription medication used to treat erectile dysfunction in men.
• Its active ingredient is sildenafil citrate, which relaxes blood vessels.
• Viagra was approved by the FDA in 1998 as the first oral treatment for ED.
• It typically takes 30 to 60 minutes to start working after ingestion.
• The effects of Viagra can last up to 4-6 hours, depending on the individual.
• Common side effects include headaches, flushing, and nasal congestion.
• Viagra should not be taken with nitrates or certain heart medications.
• Overuse or misuse can lead to serious health complications.

Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. VIAGRA was shown to potentiate the hypotensive effects of nitrates and its administration in patients who use nitric oxide donors such as organic nitrates or organic nitrites in any form is therefore contraindicated [see Contraindications (4.1), Drug Interactions (7.1), and Clinical Pharmacology (12.2)]. When VIAGRA is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating VIAGRA treatment and VIAGRA should be initiated at 25 mg [see Warnings and Precautions (5.5), Drug Interactions (7.2), and Clinical Pharmacology (12.2)].

Adverse effects

Goldstein, Lue, Padma-Nathan, Rosen, and Steers have served as consultants to Pfizer, manufacturer of sildenafil, as well as to other companies making products for the treatment of erectile dysfunction. We are indebted to all the investigators who participated in the trials; to Dr. Ian Osterloh and Dr. David Cox of Pfizer for their help with the study design and logistics; to Dr. Michael Collins and Dr.

What can I do to make Viagra work faster?

Michael Smith of Pfizer for their assistance with data analysis; and to Dr. Patricia Leinen and Dr. Michael Sweeney for aid in the preparation of the manuscript. The other members of the Sildenafil Study Group are S. Auerbach, Newport Beach, Calif.; A.L. The recommended dose for ritonavir-treated patients is 25 mg prior to sexual activity and the recommended maximum dose is 25 mg within a 48 hour period because concomitant administration increased the blood levels of sildenafil by 11-fold [see Warnings and Precautions (5.6), Drug Interactions (7.4), and Clinical Pharmacology (12.3)]. Consider a starting dose of 25 mg in patients treated with strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, or saquinavir) or erythromycin. Clinical data have shown that co-administration with saquinavir or erythromycin increased plasma levels of sildenafil by about 3 fold [see Drug Interactions (7.4) and Clinical Pharmacology (12.3)].

Aspect	Description	Notes
FDA Approval	Approved for erectile dysfunction and pulmonary hypertension	Ensures safety and efficacy
Prescription Requirement	Yes, prescription needed in most countries	Legal distribution restrictions
Counterfeit Risks	High risk online; authenticity varies	Purchase from reputable sources
Patent Duration	Patented until 2020s; generics now available	Price reduction post-patent expiry
Advertising Regulations	Strict rules on direct-to-consumer advertising	Limits false or misleading claims

Consider a starting dose of 25 mg in patients > 65 years, patients with hepatic impairment (e.g., cirrhosis), and patients with severe renal impairment (creatinine clearance <30 mL/minute) because administration of VIAGRA in these patients resulted in higher plasma levels of sildenafil [see Use in Specific Populations (8.5, 8.6, 8.7) and Clinical Pharmacology (12.3)]. VIAGRA is supplied as blue, film-coated, rounded-diamond-shaped tablets containing sildenafil citrate equivalent to 25 mg, 50 mg, or 100 mg of sildenafil.

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