As others have stated, patient education and responsibility is key; however, medical professionals, drug companies, and researchers definitely still have a huge role to play. There have been deadly mistakes by doctors and pharmacies. While patients need to keep a list of what medications they are taking, the medical professionals need to be proactive and really listen to concerns and symptoms that some patients may be having before prescribing them more or different medicine.
Patient education is, as others on the thread have pointed out, the key. If you're taking medication, you need to familiarize yourself with its side effects, and the drugs that it can react harmfully with. That would be sort of the first line of defense. I've often thought that doctors, when they prescribe these medications, ought to double-check with the patients as to what other drugs they are taking. In this day and age, when there is so much information out there, there really is no reason not to think about it and act responsibly, whether you are a caregiver or a patient.
The best way to prevent drug interactions starts with the patient. The patient needs to let their health care providers (doctors, pharmacist, etc) know about every medication they are taking including herbal supplements and over the counter medications. Each time a patient picks up a prescription, a medication pamphlet is attached to the prescription bag. It is the patients responsibility to read this pamphlet. A patient who understands what side effects to look for as well as what drugs could interact is much better prepared to avoid harmful interactions. A patient should ask their doctor or pharmacists questions about medication interaction before beginning the medication. Any questions not answered by a health care provider or the medication pamphlet can easily be found on the the Internet at sites like the FDA, the CDC, and the medication's producer. As a society, we need to teach patients how to be better advocates.
Although there is an amazing amount of misinformation and outright fabrication online, I think that in many cases the Internet should be your first and best resource for drug interactions. Every site has an opinion; I would trust the FDA, CDC, and similar sources before I went to alternative sites. Also, check hospital and local medical institution sites for easier access to information; a lot of medical sites have life staffers available to chat and answer questions.
Here is another perspective. I think many would agree that we are over-drugged as a society. Hence, there might be some merit in starting a campaign to tell people not to think twice before taking even legal over the counter medication. With that said, another possible way to help people not take dangerous combination of drugs is to provide a fact sheet, every time a person picks up medication at the pharmacy. This should not be difficult to do. All you need is a database. All the pharmacist needs to do it type in the drug and press print.
I agree with the above posters that a person needs to be informed. There is no other way to be informed than for the information to be out there to find in the first place. Therefore, both society (drug companies/researchers) need to work with individuals wanting information on the drugs/medications that they are taking.
On a societal level, I think that the best thing to do would be to make a database available online and publicize it well. You ought to be able to go online, look up the drug you are going to be taking, and see all the possible interactions it might have with other drugs, with alcohol, etc.
The first and most important personal step is to be responsible for the monitoring of my own personal medications. This involves obtaining all my medications from a single source so the pharmacist is able to help me track possible interactions. It means I need to be proactive in asking my pharmacist, doctor, nurse, therapist, and anyone else who might want to prescribe a medication for me if it is really needed, what side effects it might cause, and what known drug interaction problems are associated with it. This means I have a list of all my regularly taken drugs (including over the counter) in my billfold along with my personal identification, so that if I were in an accident and unable to communicate, the EMTs and others providing first aid would be able to become aware of drugs in my system before they started adding more medications.