This is often the question that most people have when talking to a pharmacist. A drug interaction is when a substance affects the activity of a prescription drug in or out of the body. This activity could be an increased effect such as higher blood pressure, a decreased effect such as decreased sex drive or some new effect that hasn’t been seen before. Today we are taking so many prescription pills that it is inevitable that drug-drug interactions will occur. There are three main groups of drug interactions. We have drug-drug interactions, food-drug interactions and drug-herb interactions.
Pharmaceutical companies can’t test every possible combination of drugs to determine what side effects or what drug interactions are possible. Pharmaceutical companies try to theorize and determine which class of drugs might be affected based on the body’s chemistry. They base their findings on what other drugs are used to a targeted area. As an example let’s use Fluoxetine (Prozac) in determining drug-drug interactions.
Fluoexetine has a negative effect with ibuprofen (used for pain relief) which causes significant intestinal bleeding with extended use. This is a good case of negative drug-drug interactions. The more complex the prescription drug, the greater the possibility of drug-drug interactions.
There are instances where your diet can negatively affect the prescription drug you are taking. Food is the basis by which we consume most of our nutrients. There are numerous prescription drugs that need to be taken with food to be absorbed by the body. Yet there are some prescription drugs that will cause side effects if taken with food.
Naproxen (Aleve) is suggested to be taken with food since it might develop ulcers when taken on an empty stomach. Grapefruit is a nice example of a food that negatively affects prescription drugs. Take Simvastatin (Zocor) as an example. Grapefruit contains furanocoumarins which slows down the body’s ability to use Simvastatin so it stays in your blood longer. High concentrations of Simvastatin circulating will become toxic and cause rashes and allergic reactions.
When we say herbs, it is not slang for the illegal kind of herb. We are discussing natural herbs on a chemical level such as oregano and thyme (rosmarinic acid). It is hard to believe that herbs can cause drug interactions but they do.
As an example Hydralazine (Apresoline) is a class of antidepressant called monoamine oxidase inhibitor (MAOI). Tyramine occurs naturally in animals and plants. It is found in high doses in most pork, alcoholic beverages, chocolate, figs, avocados, bananas, soy sauces and certain aged cheeses just to name a few. Hydralazine in the presence of tyramine causes hypertensive crisis in which blood pressure increases tremendously followed by organ damage and even the possibility of stroke. As you can see, you have to strictly watch what you eat when using Hydralazine. That is also why Hydralazine is used as a prescription drug of last resort.
The study of drug interactions is complex and never ending. As new drugs are brought to market and doctors report back with additional side effects, drug interactions can be closely monitored. The development of prescription drugs occurs in a controlled laboratory environment until clinical trial. Until that prescription drug is exposed to the real mix of prescription drugs, no one knows for sure what the drug-drug interactions will be.