What factors can affect when taking viagra?
Given the need for your body to metabolize Viagra, eating a large meal before using Viagra can slow down the absorption of the drug into your bloodstream. Conversely, the slowdown could make the effects last longer.
Mixing it with Viagra and Caffeine could lead to some side effects like headaches listed here https://www.edrugstore.com/blog/erectile-dysfunction/viagra/caffeine-vodka-red-bull-and-viagra/?amp =1
In general, all questions regarding the use of Viagra are best discussed with your doctor.