What can happen to a person tht drinks nd at the same time takes medication over the counter?

Depends on drinking. How much of what, and what otc drugs you are talking about. Anything that is potentially sedating, like antihistamines that are in cold/allergy medications or otc sleeping aids, can cause major problems when taken with excessive amounts of alcohol. If we are talking 1 or 2 standard drinks, probably few if any problems, but higher doses of alcohol can cause harm.
It depends on the me. If a person is drinking alcohol and is taking prescription medication or even over the counter medicine at the same time, it can sometimes make a person get very sick with nausea and vomiting. Other side effects may be to cause central nervous system depression-your mind gets sleepy and you don't think as clearly as without the medicine. Your reaction time may also be impaired/slower.