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Pfizer, maker of blockbuster erectile dysfunction drug Viagra, is expected to face new competitors in the UK when its patent on the drug's process expires later this month.
This animation explains the malfunctioning chemical process which Viagra's active ingredient treats.
During sexual arousal, the brain signals nerves fibers in arteries. These fibers release nitric oxide which triggers a chemical reaction. Cyclic guanosine monophosphate (cGMP) is then released causing the arteries' walls to relax, increasing blood flow and producing an erection."
Meanwhile, the enzyme phosphodiesterase-5, (PDE5) is counteracting the cGMP. As long arousal continues, the heightened blood flow and erection is maintained.
In cases of erectile disfunction, insufficient cGMP is produced and is overwhelmed by PDE5.
Viagra contains a PDE inhibitor which bonds with the enzyme and stops it from counteracting the cGMP. This allows enough of the chemical to accumulate and relax the artery walls, producing an erection.
Take between 30 and 60 minutes (and up to 4 hours) before sex; works for about 4 hoursRecommended dose for most men is 50mgs; after that, dosage may go to as high as 100mg, or as low as 25mg, which may be prescribed for men over 65.Quickly absorbed by the body, less effective after a high-fat meal, and best taken on an empty stomach. Erectile Dysfunction Drugs Comparison Chart Compare Viagra, Cialis, Levitra
Take 1 hour before sex; works for 4 to 5 hours, and may be slightly more effective than ViagraStarting dose for most men is 10mgs a day, but men over 65 often start on the 5mg pill.Can be taken with or without food, although slightly less effective after a high-fat meal. Avoid anything containing grapefruit juice; it may make side effects worse. Cialis New Viagra for femalesAchat Cialis sans ordonnanceWhat if a woman took CialisGeneric Cialis cheapest priceBuy Viagra for cheapHow does Viagra worksViagra delivery UKCialis works goodFree Viagra order online Comes in two forms. The daily pill stays effective in between doses, but may take 4 to 5 days before it begins working. The “weekender” version of Cialis can start working in as little as 30 minutes for men who take the highest dose of the drug (20mgs); it stays effective in the body for up for 36 hours.Daily pill comes in both a 2.5mg and 5mg tablet; most men start with the lower dose. The use-as-needed, “weekender” pill comes in 5, 10 and 20mg strengths; recommended starting dose is 10mg,Can be taken with or without food. Avoid heavy drinking (5 glasses of wine or 5 shots of whiskey); when combined with Cialis, it can lead to headaches, dizziness, an increase in heart rate, and a drop in blood pressure.