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Biotech / Medical : VVUS: VIVUS INC. (NASDAQ)
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To: AlienTech who wrote (12019)7/23/1998 11:13:00 AM
From: DaiS  Read Replies (1) of 23519
 
Why has the FDA now flagged up this study correction. I never saw that site before, it has all the data on all the different tests. For the eye study you can see the ammendment memorandum and the original study.

The original study had 8 normal subjects and 7 diabetics. 'Three normal and 4 diabetic subjects reported color-related visual disturbances, all shortly after exposure to sildenafil..' (they were on 200mg). On their web site Pfizer refer to 3% of men having visual disturbance - good job isn't it that the clinically effective dose is not 200mg, Pfizer were lucky there.

I don't know much about vision but if you scan Table 1 in the memorandum, there is not much difference between placebo and sildenafil and given the small number of individuals examined - does this ring a bell? - this is not surprising. What stands out immediately however is the increase in blue wave amplitude with sildenafil. It is this that is flagged in the original article - abnormal blue vision. The difference is VERY large, but because of small sample size is only just, or is marginally significant.

However what appears to happen in the memorandum (penultimate paragraph) is that they argue essentially that the difference is non-significant by saying that such individual significant differences may be expected by chance, even with random data, when many comparisons are made. In statistical jargon - the result is significant in an a priori test (when you have no prior hypothesis) but is not significant in an a posteriori test.

The bottom line is that the experiment should have been repeated with larger sample size at the time.

IMO of course

DaiS
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