erectile dysfunction

Erectile dysfunction (ED)is the inability to reach and maintain an erection (hard-on)satisfactory for a sexual intercourse. Viagra is definitely the most popular, and the most used drug for the treatment of this disease.

Even if you do not belong to the category of people who buy products for the treatment of erectile dysfunction, you must have heard of Viagra. It is probably one of the most popular pills in the world, and is accidentally discovered by a pharmaceutical giant called Pfizer during a clinical trial of heart disease treatment.

It contains an active substance called Sildenafil.Sildenafil is a potent inhibitor of cyclic guanosine monophosphate (cGMP) specific phosphodiesterase type 5 (PDE5) in the cavernous body of the penis. By inhibition of this enzyme, Viagra leads to relaxation of the cavernous body, thereby enabling erection. However, in order for Viagra to work, sexual stimulation is needed. Its effectstarts within 30 minutes after oral administration and lasts for 4-5 hours.

Contraindications and Precautions

Viagra should not be used in people who are allergic to the active substance Sildenafil, or other chemically similar substances, such as Tadalafil (Cialis), or Vardenafil (Levitra).

Concurrent administration of Viagra with a drug called Riociguat(stimulator of guanylate cyclase used to treat pulmonary hypertension) is contraindicated. Viagra can also interact with the following drugs:

  • Calcium channel blockers, such as Amlodipine (used to treat hypertension).
  • Ritonavir – a medicine used to treat HIV.
  • Clarithromycin, Telithromycin, Erythromycin – antibiotics used to treat bacterial infections. These antibiotics significantly increase Viagra blood levels, thus increasing risk of side effects.
  • Amprenavir, Atazanavir, Cobicistat, and Indinavir – drugs used to treat HIV. Concomitant use increases the risk of lightheadedness, tinnitus, nausea, vision loss, hearing loss, chest pain, priapism, irregular heartbeat and fainting.
  • Grapefruit or grapefruit juice. Grapefruit may increase blood levels of Viagra therefore it should not be used while taking this drug.
  • Antifungal drugs, such as Itraconazole, Ketoconazole, and Fluconazole. These drugs inhibit the enzyme through which Viagra is metabolized, thus leading to increased Viagra blood levels. Call your doctor if you notice nausea, palpitations, arrhythmias, visual disturbances and fainting.

Since clinical studies have shown that Viagra can cause anterior ischemic optic neuropathy, this drug is contraindicated in patients who have a positive history of ischemic optic neuropathy, whether it is associated with the use of the PDE5 inhibitor or not.

Due to lack of clinical studies that would confirm the safety of its use, Viagra should not be used in the following conditions:

  • Hypotension – low blood pressure (<90/50 mmHg).
  • Recently suffered heart attack or stroke.
  • Retinitis pigmentosa– hereditary, degenerative eye disease.
  • Severe liver or kidney damage.

Viagra must be very carefully applied in patients suffering from cardiovascular diseases because the active substanceSildenafilexhibits vasodilatory effect (widens blood vessels and lowers blood pressure). Due to this effect, clinically significant interactions with nitrates have been observed with drugs used for the treatment of angina pectoris, such as nitroglycerin, isosorbidedinitrate, isosorbidemononitrate, and amyl nitrite.

Dosage

The recommended dose is 50mgthat should be taken 30-60 minutes before the planned sexual intercourse. If this dosage is too strong for you, then it can be reduced to 25mg. The maximum daily dose is 100mg.

Viagra should not be taken more than once a day.It is best to take the pill on an empty stomach, because foods slow down the effects of Viagra. Simultaneous use with alcoholic drinks reduces the effectiveness of this drug.

It is not recommended for use in patients under the age of 18, and above the age of 65.

Overdose:Clinical trials that observed effects of Viagra in a dose of 800mg/day have shown that high doses cause side effects more frequently, including headache, hot flushes, dizziness, dyspepsia, stuffy nose, and visual disturbances. Therefore, taking doses greater than 200mg/day is not recommended.In case of an overdose, supportive measures should be applied.

 

Side Effects of Viagra

The most common side effect of Generic Viagra is headache, which occurs due to the widening of blood vessels in the brain. Usually, the headache rapidly disappears after stoppingthe treatment.

Common side effects (affect1-10% of patients) of Viagra include:

  • Dizziness
  • Blurred vision
  • Hot flushes
  • Perception disorders
  • Stuffy nose
  • Nausea
  • Digestions disorders
  • Dyspepsia
  • Visual disturbances

Occasional side effects (affect0.1-1% of patients) include:

  • Somnolence
  • Rhinitis
  • Photophobia
  • Conjunctivitis
  • Vertigo
  • Tinnitus
  • Hypertension – high blood pressure
  • Hypotension – low blood pressure
  • Tachycardia – rapid heartbeat
  • Palpitations
  • Sinus congestion
  • Muscle pain
  • Abdominal pain
  • Epistaxis (nosebleeds)
  • Chest pain
  • Limb pain
  • Muscle pain
  • Hematuria – presence of red blood cells in the urine
  • Photopsia – presence of perceived flashes of light
  • Eye pain
  • Fatigue

Rare side effects (affect0.01-0.1% of patients) include:

  • Convulsions
  • Arteriosclerotic retinopathy
  • Nonarteritic anterior ischemic optic neuropathy
  • Occlusion of retinal artery
  • Retinal hemorrhage
  • Glaucoma
  • Dilation of pupils
  • Eye irritation
  • Double vision
  • The swelling of the eyes
  • Loss of hearing
  • Changed color perception
  • Sudden cardiac death
  • Ventricular arrhythmias
  • Unstable angina
  • Heart attack
  • Irritability
  • Penis hemorrhage
  • Priapism – painful and long erections (lasting for more than 6 hours)
  • Steven-Johnson syndrome
  • Toxic epidermal necrolysis
  • Cerebrovascular adverse events (stroke, convulsions, syncope)
  • Feeling of numbness in the mouth (oral hypoesthesia)

You should inform your doctor if you experience any adverse effects. Avoid using doses higher than recommended, because this greatly increases risk of side effects.

Where Can You Legally Buy Viagra?

In most countries, Viagra cannot be purchased without a prescription. However, it is legal to buy Viagra online, as long as you use it for your own purposes. But be careful, choose only reliable and verified online pharmacies to avoid a fraud.

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