Paul goes to the doctor for an infection. His doctor writes two prescriptions and tell him that he must take both drugs if he wants to get better and that if he takes only one drug, he might not get better. He notice that they are both anitbiotics and wonder why he must take two instead of one. Is the doctor just trying to make Paul buy more drugs?
Taking two antibiotics at the same time is safe and can sometimes be the most effective treatment. If a bacterial infection is particularly bad or in a difficult to treat location, a combination of two different types of antibiotics can be used to make sure that the infection is fully eliminated. Once might be a more targeted antibiotic and the other a more broad spectrum antibiotic. The most important thing to remember is that once an antibiotic regimen is started it should be fully completed, even if you feel better before the medication cycle is complete. This is to make absolutely sure that all of the bacteria has been eradicated and cannot come back as more resistant to the drug. So the doctor is probably acting in Paul's best interest and not trying to make him spend more money.