Vivus: into single digits Message Board

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Biotech / Medical : Vivus: into single digits

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To: BigKNY3 who wrote (64)	2/17/1998 3:05:00 PM
From: Tunica Albuginea	of 1016

Big K, concerning " blue halos " side effect of Viagra and possible retinal degeneration/ blindness. I have made several calls and found out several items. I will post some of the preliminary findings and replies to your points. First however let me point out you still have not told us why patients get blue halos. This can be an early sign of toxicity. For example "color vision " seen when a patient is on digitalis, means that it is at toxic levels with risk of sudden cardiac death due to an arrhythmia. The points: 1)"In the definitive research book on PDEs "Phosphodiesterase Inhibitors" by Christian Schudt et al, Academic Press." Answer: -Book was published in 1996. Their data thus only goes to ~ 1993 ( there is usually a 2-3 year lag on references ). -from reading your post one could get the opinion that the word "definitive" means that that's it. All work is done, and this is all there is to know and this is not so in fact as I will point out. 2)"-"The type VI PDEs are found in the photoreceptors and are involved in visual signaling pathways". Answer: - the reason PDE VI have been primarily described in the retina is because =it is the most abundant =it is the most easily reached in the surface aerea, in the rods. -fact is that PDE VI was initially part of PDE V !!;( PDEV is the one in the penis, the one that Viagra inhibits ). -PDE V was later separated into PDE V and VI; BUT, 75% OF penile PDE V has the SAME STRUCTURE as retinal PDE VI and share the same characteristics and possibly react the same to Viagra. - The PDE content of retinal cones is not known and can very well contain PDE V. I can't comment on the textbook you have quoted because it is a subreference book. I am in the process of getting it through interlibrary loan and I will comment when I see it. It is very easy to quote something out of context. Again, so far what we know for sure is that: -Patients on Viagra get "blue halos", [ and "other visual disturbances" per DrBennett's article in Feb (* Geriatrics, that I posted earlier ).] -Color disturbances can be a sign of some form of tissue injury. -No Retinal Electrograms were done that we know off on patients receiving Viagra, which is the only sure way to detect early retinal damage. -PDEs as a group are a very toxic group of drugs; thus it would be unusual for one of them (n Viagra) to be different. however am still in process of gathering more data. I will post as they come in. TA

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