Drug Interactions – Are you at risk?

Integrative Clinical Pharmacist Scott Berliner, RPh

Consider the vast number of prescription medications, over-the-counter drugs, vitamins, minerals, and herbal supplements on the market today. A compelling statistic from SUNY College of Pharmacy remarked that someone who is taking a combination of any six drugs, vitamins, minerals, or herbs, has an 80 percent chance of an interaction of some kind. At certain times of year, allergies are wreaking havoc with our sinuses, causing headaches and congestion, and simple aches and pains arise from doing yard work or playing outdoors. Anybody could reach the six medication/supplement combination threshold easily, increasing the risk for an interaction.

Why are drug interactions such a big deal? Prescription drug dosages need to be high enough to help fight a specific disease, and low enough to avoid causing serious side effects. Taking other prescription drugs, non-prescription drugs, recreational drugs, herbal products, vitamins or even food can cause large changes in the amount of medication in your bloodstream. This is called a “drug interaction.” Having too much of a drug in your bloodstream can cause serious side effects, and too little can mean that the drug will not work. These interactions are likely because whether it is a drug, herb, or vitamin, on its journey through the body, the relative pathway it will travel is the same. This pathway is studied in a specific science called “pharmacokinetics.” Basically, pharmacokinetics refers to the absorption, distribution, metabolism, and elimination of drugs and supplements. Drugs and supplements can interact at any stage of the pathway.

More specifically, absorption is how the drug, vitamin, or herb enters the bloodstream, usually from tablets or capsules, entering the stomach and intestines. For some products, the amount of acid or food in the stomach can substantially alter absorption. This is why some products have food requirements, such as “take on empty stomach”, “take with food”, or “take with fatty foods”, or why some have warnings not to take antacids with the drug. Many forms of calcium for the bone are similar to antacids, and can have the same affect on absorption.

Distribution, the next step in the pathway, is the movement of a drug from the bloodstream to various areas of the body and the relative proportions of drug in the tissues. Many things can affect distribution including, but not limited to, weight, age, dehydration, or the specific chemical structure of drug.

Metabolism is how the body chemically changes a drug, usually in the intestines and liver. Metabolism involves changing the drug by breaking it down or adding a chemical that makes it easier to pass into urine or stool. Many interactions occur because one substance interferes with the metabolism of another (called inhibition). Inhibition causes higher drug levels in the bloodstream. On the other hand, a substance can also speed up metabolism (called induction). Induction causes lower drug levels in the bloodstream.

The most common drug interactions involve the liver. Several substances can slow down or speed up the action of liver enzymes. This can cause dramatic changes in the blood levels of other drugs that are broken down or changed by the same enzyme. A few drugs slow down excretion of substances through the kidneys, which increases the blood levels of substances that are normally removed by the kidneys.

Finally, elimination is how the body gets the drug out , which is usually by passing the drug into the urine (via the kidneys) or stool (via the liver). Some forms of kidney or liver illness can cause the blood levels of some drugs to build to very high levels if the drug dose is not reduced.

Age can also be a significant factor in drug interactions. Children and the elderly are of greatest concern because they are more likely to have under-functioning kidneys or livers. Generally, older adults are more likely to experience adverse effects from medications. This is due not only to the number of drugs they use, but also to the age-associated changes that affect the body’s use of these drugs. Older people typically have more disorders than children and younger adults, and thus usually take more medications and supplements. Basically, the more drugs people take, the more likely they are to have problems caused by a drug interfering with another drug or disease state. Also, with aging, people may have more difficulty following complicated instructions for taking drugs, such as taking the drug at very specific times or avoiding certain foods.

For all these reasons, and many more not listed in this article, it is vitally important to screen for possible interactions. Just because you are able to purchase products such as over-the-counter drugs, vitamins, minerals, and herbal supplements without a prescription, doesn’t mean that they are always free of harmful effects. It’s always a good idea to consult with a physician and/or pharmacist who has an understanding of herbal supplements, vitamins, medications and their various interactions before you add anything to your regimen.