Crazy Viagra blog.

Viagra, an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). 

The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of nitric oxide (NO) by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. 

Studies in vitro have shown that sildenafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (10-fold for PDE6, >80-fold for PDE1, >700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11). The approximately 4,000-fold selectivity for PDE5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility. Sildenafil is only about 10-fold as potent for PDE5 compared to PDE6, an enzyme found in the retina which is involved in the phototransduction pathway of the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels (see Pharmacodynamics). 

In addition to human corpus cavernosum smooth muscle, PDE5 is also found in lower concentrations in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle. The inhibition of PDE5 in these tissues by sildenafil may be the basis for the enhanced platelet antiaggregatory activity of nitric oxide observed in vitro, an inhibition of platelet thrombus formation in vivo and peripheral arterial-venous dilatation in vivo.

What is Viagra?

Viagra is a prescription medicine taken by mouth for the treatment of erectile dysfunction (ED) in men. ED is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. Viagra may help a man with ED get and keep an erection when he is sexually excited. Viagra must be used only under a doctor’s care.

Viagra does not:

• cure ED
• increase a man’s sexual desire
• protect a man or his partner from sexually transmitted diseases, including HIV. Speak to your healthcare professional about ways to guard against sexually transmitted diseases.
• serve as a male form of birth control

Viagra is only for men with ED. Viagra is not for women or children. Viagra must be used only under a healthcare professional’s care.

Who Should Not Take Viagra?

Do not take Viagra if you:

• take any medicines called “nitrates”
• use recreational drugs called “poppers” like amyl nitrate and butyl nitrate
• have been told by your healthcare professional to not have sexual activity because of health problems

What are The Risks?

The following are the major possible risks and side effects of Viagra therapy. This list is not complete.

Viagra can cause your blood pressure to drop suddenly to an unsafe level if it is taken with certain other medicines such as nitrates and alpha-blockers, and recreational drugs that contain nitrates called “poppers”. A sudden drop in your blood pressure could cause you to become dizzy, faint, or have a heart attack or stroke.

Tell all your healthcare professionals that you take Viagra. If you need emergency medical care for a heart problem, it will be important for your healthcare professionals to know when you last took Viagra.

Viagra may uncommonly cause:

• an erection that won’t go away (priapism)
• vision changes, such as seeing a blue tinge to objects or having difficulty telling the difference between the colors blue and green

Some common side effects with Viagra include:

• headache
• flushing
• upset stomach
• stuffy or runny nose
• urinary tract infection
• diarrhea

What Should I Tell My Healthcare Professional?

Tell your healthcare professional if you:

• have or had heart problems
• have low blood pressure or have high blood pressure that is not controlled
• have had a stroke
• have liver problems
• have ever had severe vision loss
• have kidney problems or require dialysis
• have retinitis pigmentosa, a rare genetic (runs in families) eye disease
• have stomach ulcers
• have a bleeding problem
• have a deformed penis shape or Peyronie’s disease
• have had an erection that lasted more than 4 hours
• have blood cell problems such as sickle cell anemia, multiple myeloma, or leukemia
• are taking a medicine called a protease inhibitor for the treatment of HIV
• are taking medicines called alpha blockers (alpha blockers are sometimes prescribed for prostate problems or high blood pressure)

Can Other Medicines or Food Affect Viagra?

Viagra and certain other medicines can interact with each other. Tell your healthcare professional about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Know the medicines you take. Keep a list of them with you to show your healthcare professional.