How does a pill know where to go in the body?

Pills or drugs are the chemical compounds which react with other specific compounds now pill got its destination by searching for its reacting material as contraceptive pills are affected b the hormones secreated by ovary so they act on their only

We can see this by taking example of any pain killer which act only on nerve ending inhibiting the impulse transfer between neurons by acting on neurotranmitter (which helps in transferring nerve impulses)

now we also encounter with side effects of drugs or pills that is because these pills some time react with other non-target tissues due to presence of those chemical by which they react.