Sildenafil

Pfizer Viagra tablet in the trademark blue diamond shape
Crystal structure of human PDE5 with bound sildenafil, PDB entry
Bulk bag of counterfeit Viagra
Sildenafil 100 milligram tablets - (prescription in the European Union)

Medication used to treat erectile dysfunction and pulmonary arterial hypertension.

- Sildenafil
Pfizer Viagra tablet in the trademark blue diamond shape

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Pulmonary hypertension

Pulmonary hypertension

Condition of increased blood pressure in the arteries of the lungs.

Condition of increased blood pressure in the arteries of the lungs.

Pulmonary hypertension
Right ventricle (on left side)
Micrograph showing arteries in pulmonary hypertensive with marked thickening of the walls.
Three major signaling pathways involved in the pathogenesis of pulmonary arterial hypertension
Phonocardiogram and jugular venous pulse tracing from a middle-aged man with pulmonary hypertension caused by cardiomyopathy. The jugular venous pulse tracing demonstrates a prominent a wave without a c or v wave being observed. The phonocardiograms (fourth left interspace and cardiac apex) show a murmur of tricuspid insufficiency and ventricular and atrial gallops.
Pulmonary artery catheter
Severe tricuspid regurgitation
Pulmonary artery hypertension and emphysema as seen on a CT scan with contrast
Cor pulmonale
4-month-old with pulmonary hypertension as seen on ultrasound

Medications specifically used to treat pulmonary hypertension include epoprostenol, treprostinil, iloprost, bosentan, ambrisentan, macitentan, and sildenafil.

Three different forms of nitroglycerin: intravenous, sublingual spray, and the nitroglycerin patch.

Nitroglycerin (medication)

Medication used for heart failure, high blood pressure, anal fissures, painful periods, and to treat and prevent chest pain caused by decreased blood flow to the heart (angina) or due to the recreational use of cocaine.

Medication used for heart failure, high blood pressure, anal fissures, painful periods, and to treat and prevent chest pain caused by decreased blood flow to the heart (angina) or due to the recreational use of cocaine.

Three different forms of nitroglycerin: intravenous, sublingual spray, and the nitroglycerin patch.

It should not be used together with medications within the sildenafil (PDE5 inhibitor) family due to the risk of low blood pressure.

role of PKG in cellular system

Cyclic guanosine monophosphate

Cyclic nucleotide derived from guanosine triphosphate (GTP).

Cyclic nucleotide derived from guanosine triphosphate (GTP).

role of PKG in cellular system

For example, Sildenafil (Viagra) and similar drugs enhance the vasodilatory effects of cGMP within the corpus cavernosum by inhibiting PDE 5 (or PDE V).

Pfizer

American multinational pharmaceutical and biotechnology corporation headquartered on 42nd Street in Manhattan, New York City.

American multinational pharmaceutical and biotechnology corporation headquartered on 42nd Street in Manhattan, New York City.

The headquarters of Pfizer In Tokyo, Japan
Charles Pfizer (1824–1906)
Bottles of Zoloft (sertraline), an antidepressant

In 1989, Pfizer scientists Peter Dunn and Albert Wood created Viagra (sildenafil) for treating high blood pressure and angina, a chest pain associated with coronary artery disease.

Cross-section of a flaccid penis

Erectile dysfunction

Type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity.

Type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity.

Cross-section of a flaccid penis
Transverse ultrasound image, ventral view of the penis. Image obtained after induction of an erection, 15 min after injection of prostaglandin E1, showing dilated sinusoids (arrows).
One ad from 1897 claims to restore "perfect manhood. Failure is impossible with our method". Another "will quickly cure you of all nervous or diseases of the generative organs, such as Lost Manhood, Insomnia, Pains in the Back, Seminal Emissions, Nervous Debility, Pimples, Unfitness to Marry, Exhausting Drains, Varicocele and Constipation". The U.S. Federal Trade Commission warns that "phony cures" exist even today.
Testosterone Supplementation - Content 88 g Gel
An unhappy wife is complaining to the qadi about her husband's impotence. Ottoman miniature.
Graphs representing the color Doppler spectrum of the flow pattern of the cavernous arteries during the erection phases. A: Single-phase flow with minimal or absent diastole when the penis is flaccid. B: Increased systolic flow and reverse diastole 25 min after injection of prostaglandin.
Longitudinal, ventral ultrasound of the penis, with pulsed mode and color Doppler. Flow of the cavernous arteries at 5, 15, and 25 min after prostaglandin injection (A, B, and C, respectively). The cavernous artery flow remains below the expected levels (at least 25–35 cm/s), which indicates ED due to arterial insufficiency.

In many cases, treatment is attempted by drugs, specifically PDE5 inhibitors (such as sildenafil ), which dilate blood vessels, allowing more blood to flow through the spongy tissue of the penis (akin to opening a valve further in order to allow more water to enter a fire hose).

Chemical structure of sildenafil (Viagra), the prototypical PDE5 inhibitor

PDE5 inhibitor

Vasodilating drug which works by blocking the degradative action of cGMP-specific phosphodiesterase type 5 (PDE5) on cyclic GMP in the smooth muscle cells lining the blood vessels supplying various tissues.

Vasodilating drug which works by blocking the degradative action of cGMP-specific phosphodiesterase type 5 (PDE5) on cyclic GMP in the smooth muscle cells lining the blood vessels supplying various tissues.

Chemical structure of sildenafil (Viagra), the prototypical PDE5 inhibitor
Tadalafil STADA Pharma - T20 - 20 mg

Sildenafil was the first effective oral treatment available for ED.

Illustration depicting angina

Angina

Chest pain or pressure, a symptom of coronary heart disease, usually due to insufficient blood flow to the heart muscle .

Chest pain or pressure, a symptom of coronary heart disease, usually due to insufficient blood flow to the heart muscle .

Illustration depicting angina
Diagram of discomfort caused by coronary artery disease. Pressure, fullness, squeezing or pain in the center of the chest. Can also feel discomfort in the neck, jaw, shoulders, back or arms.

Nitroglycerin should not be given if certain inhibitors such as sildenafil, tadalafil, or vardenafil have been taken within the previous 12 hours as the combination of the two could cause a serious drop in blood pressure.

Bulk bag of counterfeit Viagra

CGMP-specific phosphodiesterase type 5

Enzyme from the phosphodiesterase class.

Enzyme from the phosphodiesterase class.

Bulk bag of counterfeit Viagra

Sildenafil, vardenafil, tadalafil, and avanafil are PDE5 inhibitors that are significantly more potent and selective than zaprinast and other early PDE5 inhibitors.

The tele tautomer (Nτ-H-histamine), on the left is more stable than the pros tautomer (Nπ-H-histamine) on the right.

Cimetidine

Histamine H2 receptor antagonist that inhibits stomach acid production.

Histamine H2 receptor antagonist that inhibits stomach acid production.

The tele tautomer (Nτ-H-histamine), on the left is more stable than the pros tautomer (Nπ-H-histamine) on the right.

Like several other medications (e.g. erythromycin), cimetidine interferes with the body's metabolization of sildenafil, causing its strength and duration to increase (therefore also its side effects to be more likely and prominent).

A flaccid penis, with surrounding pubic hair removed to show anatomical detail

Human penis

External male intromittent organ that additionally serves as the urinal duct.

External male intromittent organ that additionally serves as the urinal duct.

A flaccid penis, with surrounding pubic hair removed to show anatomical detail
Lateral cross section of the penis
Anatomical diagram of a human penis
Various sized penises
Stages in the development of the male external genitalia
A urinating puer mingens by Annibale Carracci, 1600, Palazzo Farnese
The development of a penile erection, also showing the foreskin gradually retracting over the glans. 
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See also: Commons image gallery''
A ventral view of a penis flaccid (left) and erect (middle); a dorsal view of a penis erect (right).
Hypospadias
Kanamara Matsuri festival in Japan
Papuan man wearing traditional penis sheath
A labelled dorsal view of a circumcised penis: (1) Shaft, (2) Circumcision scar, (3) Corona, (4) Glans, (5) Meatus.
Dissection showing the fascia of the penis as well as several surrounding structures
Image showing innervation and blood-supply of the human male external genitalia

Erectile dysfunction is the inability to develop and maintain an erection sufficiently firm for satisfactory sexual performance. Diabetes is a leading cause, as is natural aging. A variety of treatments exist, most notably including the phosphodiesterase type 5 inhibitor drugs (such as sildenafil citrate, marketed as Viagra), which work by vasodilation.