Remember those chemistry projects in high school where you mixed two innocuous compounds and got a strange reaction? When you take two prescriptions at the same time, you may be doing a similar experiment on yourself. When certain medications are combined, they have a powerful reaction and can have dangerous side effects. Drug interactions can be fatal in rare situations.
Drugs can interact with one another in a variety of ways. A medication’s action can often be blocked or enhanced by another. Antibiotics, for example, can be less effective when taken with certain over-the-counter antacids (see below). In some circumstances, medications may interact too well with one another. Aspirin and the prescription medicine warfarin (Coumadin), for example, can thin the blood and help prevent blood clots. However, when used together, they can increase the risk of major bleeding.
What should I be on the lookout for?
Fortunately, you can take precautions to avoid potentially harmful drug interactions. First and foremost, inform all of your doctors about all of your existing medications, including over-the-counter medications and herbal medicines. Every doctor’s appointment should ideally include a list of your prescriptions. Better still, bring all of your medications to your doctor’s office so you can discuss them. You should also read the labels on all of your drugs carefully. If you have any concerns, don’t hesitate to seek advice from your doctor or pharmacist.
You might also want to do some preliminary study on possible interactions so that you’re better prepared when you see your doctor or pharmacist. Every prescription comes with a package insert that explains the drug’s potency, dose, and adverse effects. If you’ve misplaced yours or thrown it away, you can look up your medication’s package insert online or ask your pharmacist for a copy. Carefully read the sections on possible side effects and drug interactions. (Some box inserts are available in consumer and medical professional versions; the handout for doctors is more comprehensive, so you may wish to request both.)
What drug combos should I stay away from?
Here are some instances of common medications that can interact with one another.
This over-the-counter pain medicine also prevents platelets in your blood from adhering together, putting you at greater risk of bleeding. When aspirin is combined with a prescription blood thinner like warfarin (Coumadin), the risk of bleeding is greatly increased. In rare situations, your doctor may advise you to take both but will do frequent blood tests to assess your blood’s clotting ability. Because aspirin can affect uric acid levels in the blood and make a gout attack worse, it should not be taken with some gout treatments.
When these infection-fighting medications are used with antacids (such as Mylanta, Maalox, or Tums) or other calcium-containing treatments, their effectiveness may be reduced. Furthermore, it has been discovered that the antibiotic rifampin reduces the efficiency of birth control pills. Other antibiotics may work in a similar way, but further research is needed. Probenecid (Benemid), an antibiotic used to treat gout, can cause antibiotic levels in the blood to rise. In some circumstances, doctors may even benefit from this interaction: Doctors occasionally prescribe this medicine in conjunction with antibiotics to give it a stronger antibacterial punch.
SSRIs, such as fluoxetine (Prozac) and paroxetine (Paxil), are newer antidepressants that should not be combined with MAOIs, which are older mood-lifters (such as phenelzine). Serotonin syndrome, a potentially life-threatening illness marked by muscle rigidity, fever, elevated blood pressure and heart rate, confusion, and possibly coma, can result from this combination. Fluoxetine and related medicines can elicit similar symptoms when combined with St. John’s wort. Confusion, fever, elevated blood pressure, and tremors are all possible side effects of such combos. Antidepressants known as tricyclics (such as Elavil) can also interact with MAOIs, resulting in disorientation, seizures, and coma.
When taken with MAOIs or tricyclic antidepressants like nortriptyline, the common medication albuterol (Proventil HFA, Ventolin HFA) can induce hazardous blood pressure rises (Aventyl, Pamelor).
Medications for the heart
When used with antacids like Maalox, the popular heart medication digoxin (Lanoxin) can lose its effectiveness. However, some other drugs, such as diazepam (Valium) and several antiarrhythmic treatments, can amplify its effects. When combined with the erectile dysfunction medicine sildenafil, nitrates can cause dangerously low blood pressure (Viagra). The blood pressure medicine atenolol (Tenormin) combined with various calcium channel blockers (particularly verapamil) can result in a potentially hazardous decrease in heart rate.
According to an American Heart Association scientific statement, administering these cholesterol-lowering treatments with a variety of heart medications can result in serious drug interactions. The statement, which was published in the journal Circulation, stated that the following medicines could create issues when used with statins:
- Fibrates are also used to reduce cholesterol levels.
- Calcium channel blockers are drugs that block calcium channels in the body.
- Blood thinners are drugs that thin the blood.
- Antiarrhythmic medications
- Medications for heart failure
- Immunosuppressive medications
Prescription and over-the-counter pharmaceuticals aren’t the only things to be concerned about. Herbal medicines like ginkgo Biloba, which slows blood clotting, can also interfere with medications. When taken with an anticoagulant like Coumadin, or ginkgo, among other herbs, can raise the risk of severe bleeding (warfarin).
Is it possible that food has an impact on how medications work?
Yes. Food has the ability to alter the way medications work in the body. Grapefruit juice, for example, inhibits enzymes that metabolize calcium channel blockers and statins, resulting in greater amounts of medicine in the bloodstream.
If you routinely consume alcohol, you should be cautious when taking over-the-counter pain medicines. If you take acetaminophen (Tylenol) with alcohol, you run the risk of liver damage, and taking aspirin, ibuprofen, or naproxen with alcohol can lead to peptic ulcers and other stomach problems.
Drug-to-drug interactions are still the main source of worry. Remember that the following list barely touches the surface of possibly harmful medication interactions.
You might wish to use internet resources to see if there are any potential interactions between the foods you eat and the medications you’re taking. Online drug checkers are available on websites for seniors, such as the AARP and those from hospitals, which can inform you about potential interactions.
There is a slew of additional possible dangers out there. Consult your doctor about the medications you have on hand. It’s possible that you’ll find out that they don’t always get along.