Paired bootstrapping

Hey everyone! Absolute newbie to R, would appreciate help with a question I have been struggling with.
Let's say I want to test the efficacy of a medicine in reducing blood pressure.
So I have a paired sample .
Three vectors are created in r. Before <-c(129,135,145,89,70) and after <-c(110,127,140,87,96)
Combined <- c(before, after)
How do I go about performing the bootstrapped version if the t-test if I want it sampled 500 times?
Thanks in advance!