Drug Interactions: Reducing Your Risk

What Is a Drug Interaction?

Drug interactions occur when one drug interacts with another drug that you are taking or when your medications interact with what you eat or drink. Drug interactions can change the way your medications act in your body. Drug interactions can make your medications less effective or they can cause unexpected and potentially dangerous side effects.

Your risk of having a drug interaction increases with the number of prescription and over-the-counter medications that you use. Moreover, the type of medications you take, your age, diet, disease, and overall health can all affect your risk. The elderly are at greater risk for drug interactions than younger adults since a larger proportion of seniors take prescription medications or over-the-counter products.

There are three important types of drug interactions:

Drug-drug interactions occur when two or more drugs interact with each other. Interactions can occur with prescription drugs, over-the-counter drugs, vitamins, and alternative medications such as supplements and herbal products.

Some examples of drug-drug interactions include:
Mixing a prescription sedative to help you sleep with an over-the-counter antihistamine for allergies can cause daytime drowsiness and make driving or operating machinery dangerous.
Combining aspirin with a prescription blood thinner such as Plavix (clopidogrel) can cause excessive bleeding.
Some over-the-counter antacids interfere with the absorption of antibiotics into the bloodstream. Certain medications used to treat fungal infections can cause serious side effects when combined with cholesterol-lowering medications such as Lipton (atorvastatin).
The herbal supplement ginkgo balboa can cause bleeding if taken with aspirin.

Drug-food interactions occur when a drug interacts with something you eat or drink.

Some examples of drug-food interactions include:
Dairy products, such as milk, yogurt and cheese, can interfere with the absorption of antibiotics into the bloodstream.
More than 50 prescription drugs are affected by grapefruit juice. Grapefruit juice inhibits an enzyme in the intestine that normally breaks down certain drugs and hence allows more of a medication to enter the blood stream.
Vegetables containing vitamin K, such as broccoli, kale and spinach, can decrease the effectiveness of drugs, such as Coumadin (warfarin), given to prevent blood clotting.
Mixing alcohol with some drugs is particularly dangerous. Alcohol interacts with most antidepressants and with other drugs that affect the brain. The combination can cause fatigue, dizziness, and slow reactions. A small amount of beer, wine, or liquor can increase your risk of stomach bleeding or liver damage when mixed with over-the-counter anti-inflammatory drugs and medications used to treat pain and fever. These drugs include aspirin, ibuprofen, and acetaminophen.

Drug-condition interactions may occur when a medication interacts with an existing health condition.

Some examples of drug-condition interactions include:
Decongestants, such as pseudo ephedrine found in many cough and cold preparations, can increase blood pressure and may be dangerous for people with hypertension. 
Beta blockers, such as Toprol XL (metoprolol) and Tenormin (atenolol), used to treat high blood pressure and certain types of heart disease can worsen the symptoms of asthma and COPD.
Diuretics, such as Hydrodiuril (hydrochlorothiazide), can increase blood sugar in people with diabetes.
What Can I Do to Help Prevent Drug Interactions?
Before starting any new prescription drug or over-the-counter drug, talk to your primary healthcare provider or pharmacist. Make sure that they are aware of any vitamins or supplements that you take.
Make sure to read the patient information handout given to you at the pharmacy. If you are not given an information sheet, ask your pharmacist for one.
Check the labels of your medications for any warnings and look for the "Drug Interaction Precaution". Read these warnings carefully.
Make a list of all your prescription medications and over-the-counter products, including drugs, vitamins, and supplements. Review this list with all healthcare providers and your pharmacist. 
If possible, use one pharmacy for all your prescription medications and over-the-counter products. This way your pharmacist has a record of all your prescription drugs and can advise you about drug interactions and side effects.

Heart Disease - Cardiovascular Drugs and Medications FAQ

Why does smoking put a person at more risk for a heart attack?

Nicotine can cause vaso constriction, ie decrease the diameter of the blood vessels. It can also increase the heart rate initially. In addition to nicotine cigarettes may contain other toxic substances which may damage the blood vessels. I mention smoking here in this section because nicotine should be thought of as a drug, and specifically a drug that can complicate cardiovascular disease.

What does taking a baby aspirin each day do to help prevent a heart attack?

Aspirin makes it less likely for the blood to clot.

Platelets and platelet products are needed for blood to clot. This is useful when we have a cut or a nose bleed, but the same process may also facilitate the clot formation which leads to a heart attack. Aspirin blocks the formation of a factor called prostaglandin which is needed to produce another clotting factor called thromboxane A2, a powerful promoter of platelet aggregation. It therefore, indirectly, lowers the platelets ability to clump together to form a clot. Small amounts of aspirin 75-100 mg are needed for this process. Typical baby aspirin measure 81 mg each.

Who should be taking a baby aspirin as a preventative treatment each day?
Not everyone is recommended to take aspirin as a heart medication.

Evidence from basic research has provided strong support for the net benefits of aspirin in decreasing the risk of cardiovascular disease (CVD) in a wide range of patients. People who are at high risk for heart disease or other vascular diseases ( primary prevention) or people who have already suffered a cardiovascular event such as a heart attack, angina, or stroke ( secondary prevention) should take aspirin.

You should not start aspirin therapy without first consulting your physician. The risks and benefits of aspirin therapy vary for each person. If you’re taking aspirin and you must undergo even a simple surgical procedure or dental extraction, you must tell the surgeon or dentist your aspirin dosage.

What is a clot busting drug?

Tissue plasminogen activator (tPA) which is a thrombolytic or clot busting agent.

When would a person be given a clot busting drug?
This is usually done if the patient goes to a hospital that doesn’t have the capability to do angioplasty. The patient is usually then transferred after the tPA treatment to a facility that is able to do the angioplasty procedure.

What are the side effects of clot busting drugs?
Stroke, gastrointestinal bleed.

What is nitro glycerin?

It is a vasodilator that dilates all blood vessels and not just the heart blood vessels. This is why a common side effect is headache.

Is that the same nitro glycerin that explodes like dynamite?
Yes.

What does nitro do to your heart that helps?
It drops the blood pressure and the heart beats more effectively.

When should you take a nitroglycerin pill?
It should be taken for chest pain that occurs on exertion, or any typical cardiac chest pain with which the patient is familiar and recognizes as heart pain as opposed to muscular pain.

Why do you put nitro under your tongue instead of swallowing them?

Absorption into the arterial system occurs faster thus providing better treatment.

Does nitro lose it’s potency over time?
Yes. Monitor the expiration date on the bottle and keep your nitroglycerin prescription updated regularly.

What kinds of things make nitro loose potency faster?
Heat and sunlight. It should be kept in an airtight sealed container in a cool dark place.

Who should carry nitro with them all the time?

Any one with a history of heart attack or angina.

What is the best way to carry nitro?

In the brown bottle that it comes in which reduces the light exposure.

Should a heart attack patient take erectile dysfunction medication?

Yes, they may as long as the patient is stable and he is not taking nitroglycerin type medications. There are some nitroglycerin type medications that are taken regularly or there are circumstances where nitroglycerin may have been taken on that day.

Are there common non-prescription drugs that a heart attack patient should avoid?
In general it is best to check with your doctor about over the counter medications. There are certain medications such as Sudafed which may increase the heart rate or blood pressure and therefore increase the demand on the heart. If the patient is on aspirin or other blood thinner then ibuprofen or other non-steroidal anti-inflammatory medications should be avoided.

What is a beta blocker drug?
Beta blockers are a class of medications which is used after heart attacks and in treatment of arrhythmias. Their main cardio protective effect is to lower the heart rate. 

Why would a patient want their heart rate lowered?
This reduces the oxygen supply and demand ratio in favor of the patient.

Are there different types of beta blockers?
The 2 main types of beta blockers are cardio-selective which mainly effect the heart cells and to a smaller extent the lung, and the non-cardio-selective B-blockers which effect the body in general. Examples of the cardio-selective blockers are atenolol, bisoprolol, and metoprolol. Non-cardio-selective blockers include propranolol, carvedilol, and nadolol.

What are the side effects of beta blocker drugs?

Some common side effects of beta blockers are Fatigue, depression, erectile dysfunction, or asthma exacerbation.

Why would a person take the drug Plavix after a heart attack?

Plavix (clopidrogel) is taken to reduce the risk of another heart attack by reducing blood clot formation.

What does Plavix do that makes it different from taking asprin?

There are multiple stages to the clotting process. While aspirin effects this process indirectly as described in the previous question, Plavix works directly on the platelet.

Clopidogrel works by preventing a natural substance called ADP (adenosine diphosphatase) from binding to its receptors on platelets. ADP is one of the chemicals in the body that cause platelets to clump together and start the process of blood clotting. As clopidogrel stops ADP from binding to platelets, it reduces the likelihood of clots forming in the blood.