In a drug interaction, a substance affects the activity of a drug. Interactions can occur between:
Sometimes, drug interactions are purposely used for a certain effect. However, often they are unwanted. In the worst case, an interaction can harm your health.
Drug-drug interactions often result from a medication affecting the body’s metabolic enzyme systems. When you take medication, your body uses metabolic enzymes to help break down and remove it. Certain medications increase the amount of some of these enzymes. This means other drugs removed by these enzymes are broken down and made inactive more quickly, weakening their effect. With vital medications, a reduced effect can be very serious. For instance, an ineffective blood thinner could lead to a stroke, blood clot, or heart attack.
On the flip side, the opposite can happen. Some medications reduce the number of certain metabolic enzymes. This in turn can make other drugs stay in the body. As medication accumulates, the risk of side effects increases. For instance, a blood pressure medication could cause an excessive drop in blood pressure, dizziness, fainting or falls. Falls can have terrible consequences, especially for an elderly person with poor bone strength. Fractures, immobility, pressure sores, and various other complications - all because of a simple drug interaction.
Combining two medications with similar therapeutic or side effects can cause another type of drug-drug interaction. For instance, glyburide and gliclazide are two medications that lower blood glucose. By taking them together, you risk dangerously low blood glucose. Similarly, combining two medications that affect the beating of the heart can lead to an irregular heartbeat.
Many people assume that herbal or ‘natural’ products are safe since they come from a natural source. However, this is not the case. Herbal products can affect your body as much as any prescription medication. They carry their fair share of interactions and side effects as well. One of the greatest challenges in dealing with drug-herb interactions is that people often do not mention the herbal products they take. As a result, it is very difficult to watch for potential interactions.
Common examples of drug-herb interactions include those with natural products such as ginger, garlic, ginseng, and St.John’s wort. Ginger is used for nausea, and garlic can lower cholesterol. Both interact with blood thinners like warfarin, plavix and Aspirin™ to raise the risk of bleeding.
Ginseng, often used to boost the immune (defence) system, increases bleeding risk. It can also lower blood glucose levels, affecting diabetes control. St. John’s Wort is most often used to treat depression. It has similarities to certain prescription anti-depressants. Mixing St. John’s Wort with prescription anti-depressants puts you at risk of severe side effects such as mania.
Almost any medication taken by mouth can cause stomach upset as a side effect. A common way to reduce this feeling of nausea is to take it with food. However, not all medications can be safely combined with food. Some medications will not absorb well. Their effectiveness is reduced. For instance, thyroid hormone tablets, certain antibiotics (like penicillin, cloxacillin, tetracycline), and sotalol are all affected by food.
Others do not react to food in general, just certain types. Grapefruit and dairy products often cause problems. Dairy products such as milk, cheese and ice cream reduce the absorption of certain drugs. The large amounts of calcium in these foods bind to drug molecules, such as those in the antibiotic ciprofloxacin.
Grapefruit interferes with a metabolic enzyme responsible for breaking down various drugs in the body. Certain medications accumulate in response, leading to a greater risk of side effects and toxicity. For instance, grapefruit affects Lipitor™ (atorvastatin) and Zocor™ (simvastatin), both common cholesterol medications. Keep in mind that this effect is unique to grapefruit. It does not apply to similar fruit like oranges, lemons or limes.
You can do many things to lessen the impact of drug interactions.
Get to know your local pharmacy staff. This gives them the chance to know you better. Take the time to talk to your pharmacist and discuss your health care goals. Whether you want to stop smoking, lose weight, or get your blood glucose under control, they can guide you in achieving your goals.
Keep all of your prescriptions at the same pharmacy. Your pharmacist then has easy access to your complete medication history on one computer system. This helps with any questions or an emergency. Report any over-the-counter medications to your pharmacist. It will be noted on your list of medications. Whenever you fill a prescription, your pharmacy team knows about everything that you are taking, including herbal and over-the-counter products. They can catch problems and drug interactions that they would not be aware of without a complete list.
Carry a wallet card listing all of your prescription and non-prescription medications. Include dose, instructions, and any allergies you may have. Show the wallet card to any health care provider caring for you. This ensures that decisions are made with complete knowledge of your entire medication history. Open and regular communication with your health care providers is the best way to lessen the risk of drug interactions.
Be sure to read the labels and handouts that come with your prescription and non-prescription medications. Taking the time to learn about medications is critical to maintaining health and avoiding drug interactions. Don’t be afraid to ask questions. Part of your health care provider’s job is to educate you and answer questions about your health.
Every year new drugs and natural products come on the market. More and more medications and supplements become available and can potentially interact with each other. Although there is no way to fully eliminate drug interactions, staying informed and proactive is the best way to protect yourself.