Safety and preliminary efficacy, pharmacokinetics ...

Unlike the other drugs, tier 2 Viagra is slightly more expensive than tier 1 on average ($17.025 vs. $16.465) and the average price of tier 3 Viagra is much higher than the other two tiers if the sample is authentic ($19.166) but much cheaper than the other two tiers if the sample is not authentic ($12.773). ................
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