Common Drug Interactions You Should Know About

Many people, including children and most especially the elderly, are taking more than one drug or supplement on a daily basis. Healthy individuals sometimes take different over-the-counter diet supplements, herbal products, energy drinks containing various chemicals, birth control pills, pain medications as needed, topical creams and ointments, and others. Patients with chronic conditions often receive prescriptions for various drugs, including supplements to boost health, and more. Most of us are not aware that we are perhaps using more than one chemically active substance that may react with other substances, including food and drinks, that may be harmful to our health. Although some reactions are not harmful, some substances may reduce or cancel the effect of another, which may or may not be a disadvantage.

Most doctors warn us about the side effects of drugs and how they may interact with each other. However, some of us do not inform our doctors about every over-the-counter (OTC) medication or supplement we are taking, which may interact with prescription drugs. Most of us also presume that OTC medications are probably safe, since one does not need a prescription to buy them. And when unexpected symptoms take place and we consult the doctor, we sometimes omit information, such as that of taking self-prescribed medications.

It is common for patients with chronic disease to receive prescriptions for more than one drug at a time. Studies show that the rate of adverse drug reactions increases exponentially when patients take at least four medications daily.

Common Types of Drug Interactions

There are various ways by which drugs can interact:

• Some drugs enhance/increase the effects of another drug. For example, taking a sedative with an antihistamine (for allergies) can cause excessive drowsiness. Fluconazole (an antifungal agent) increases the blood levels of warfarin (an anti-clotting drug), which can result in increased tendency for internal bleeding.

• Some drugs reduce the effects of another drug. For example, calcium supplements decrease the absorption of some antibiotics like tetracycline if they are taken together. Antacids and oral iron supplements also reduce the absorption of antibiotics like azithromycin and tetracycline in the gastrointestinal tract. St. John's wort, a popularly used herbal product, reduces the therapeutic effects of some drugs, including digoxin, a heart medication, and Cyclosporine, an immunosuppressant, by increasing their breakdown.

• Combining some medications can cause bizarre side effects. For example, an antidepressant combined with a prescription pain reliever can lead to delirium, euphoria, and restlessness.

• Taking some drugs with certain foods or beverages such as alcohol can cause side effects like excessive drowsiness and heart irregularities. Spinach and broccoli may reduce the effects of warfarin, while grapefruit juice increases the effects of other drugs, including felodipine (for high blood pressure). Taking some antibiotics with milk products can reduce their absorption, thus reducing their therapeutic effects. People who smoke may need to take higher dosages of certain drugs (such as theophylline), since it increases the latter's clearance from the blood, making it less effective.

• Drug-disease interactions occur when a drug exacerbates a pre-existing medical condition or when the presence of a specific disease alters the expected effect of a drug. Recognizing and understanding these interactions is crucial to preventing unwanted side effects and ensuring the optimal therapeutic outcome for the patient. For example, nonsteroidal anti-inflammatory drugs (NSAIDs), like ibuprofen, can elevate blood pressure and reduce the effectiveness of antihypertensive medications. NSAIDs can also exacerbate heart failure due to fluid retention. Some anti-diabetic drugs might also pose a risk to heart failure patients.

• Drug-environment interactions refer to changes in the effect or side effects of a medication due to environmental factors. These interactions can be caused by various environmental exposures, including temperature, humidity, altitude, air pollution, and radiation (like sunlight). Recognizing these interactions is important to prevent unwanted effects and achieve the best therapeutic outcome. Some drugs can make the skin more sensitive to the damaging effects of UV radiation, leading to an increased risk of sunburn or other skin reactions when exposed to sunlight. Examples include certain antibiotics (like tetracyclines and sulfa drugs), thiazide diuretics, and some antipsychotic medications.

See Also: Are Brand Name Drugs Better Than Their Generic Equivalents?

Drugs Interacting with Disease

Drugs can interact with a medical condition, such as high blood pressure, to make it worse or produce other side effects. Examples of common medications that can increase blood pressure readings are nasal decongestants and anti-allergy drugs that contain phenylephrine, which can tighten blood vessels. In people who have advanced liver disease or kidney disease, drug metabolism and excretion may be decreased, which may lead to exaggerated drug effects and toxicity. Therefore, a relatively safe drug such as acetaminophen can cause toxic effects in a person who has liver cirrhosis.

Factors Leading To Drug Interactions

Studies show that drug interactions significantly contribute to the number of hospital admissions and ER visits. There are various factors that lead to patients taking drugs that can cause unwanted effects and interactions. One study has demonstrated that more than 20% of its participants are taking at least one drug that can worsen their existing condition. In some cases, drugs taken together by participants were found to work against each other in a competitive manner. One factor that contributed to this was that participants had coexisting conditions, for which physicians prescribed medications that worked for one condition but worked against the other condition. Examples of medical conditions that can compete with each other include diabetes and hypertension, and coronary artery disease and diabetes.

Avoid Adverse Side Effects and Drug Interactions

Many patients take prescribed drugs from their doctors, trusting that these will help improve their condition. However, if you feel that something is causing you to experience symptoms that were not there before, or if you feel that your medications are not working as they should, inform your doctor about it. Ask him/her for more information on the expected therapeutic effects and side effects that may occur with your drugs. You can also inquire about the effects of diet on drug intake. Knowing how to take combinations of drugs and which ones should not be taken together also helps reduce drug competition and drug interactions.

Inform your doctor if you are taking other OTC medications or dietary supplements, since they may affect the action of prescribed drugs. Ask your pharmacist for more information about OTC drugs and learn how to read labels. Look for the following information when reading labels:

• active ingredients, their amount and purpose

• inactive ingredients

• indications or uses of the drug/supplement

• directions on how to take the drug, including any special instructions

• dosage recommended

• warnings on the label, which includes drug interactions

• date of expiration

See Also: The Dangers Of Prescription Drugs

Many people are convinced to take various types of dietary supplements, nutritional products, and other over-the counter antibiotics after hearing other people's advice or reading promising claims in the internet. Studies suggest that people often self-medicate because it is more convenient and less costly than going to a doctor's clinic. However, one risks taking inappropriate medications and suffering from dangerous side effects in doing so. Caution is likewise advised, especially for elderly patients, pregnant or lactating women, and patients with chronic conditions, in taking medications without proper medical consultation.