drugs
Drug Interactions
Drug Drug Interactions
Drug-drug interactions can involve prescription or nonprescription (over-the-counter) drugs. Types of drug-drug interactions include duplication, opposition (antagonism), and alteration of what the body does to one or both drugs. When two drugs with the same effect are taken, their side effects may be intensified. Duplication may occur when people inadvertently take two drugs (often at least one is an Overview of Over-the-Counter Drugs ) that have the same active ingredient. For example, people may take a cold remedy and a sleep aid, both of which contain Awareness of drug ingredients is important, as is checking each new drug to avoid duplication. For example, many prescription-strength pain relievers contain an opioid plusacetaminophen. People taking such a product who do not know its ingredients might take over-the-counteracetaminophenfor extra relief, risking toxicity. Similar problems with duplication can arise when two different drugs with the same effect are taken. This is most likely to occur when people see several doctors, obtain prescriptions at more than one pharmacy, or both. Doctors who are not aware of what others have prescribed may inadvertently prescribe similar drugs. For example, excessive sedation and dizziness can occur when two doctors both prescribe a sleep aid or when one prescribes a sleep aid and the other prescribes another drug (such as an antianxiety drug) that has similar sedative effects. People can reduce the risk of this kind of duplication by keeping each doctor informed about all drugs being taken and by using one pharmacy to obtain all prescriptions. It is helpful to keep an up-to-date written list of all drugs being taken and to bring the list along on each doctor visit. Also, people should not take previously prescribed drugs (such as a sleeping pill or pain reliever) without checking with the doctor or pharmacist because that drug may duplicate or otherwise interact with one of their current drugs. Two drugs with opposing actions can interact, thereby reducing the effectiveness of one or both. For example, Nonsteroidal Anti-Inflammatory Drugs (NSAIDs), such as One drug may alter how the body absorbs, distributes, metabolizes, or excretes another drug (see Introduction to Administration and Kinetics of Drugs ). Consult the doctor or pharmacist before taking any new drugs, including over-the-counter drugs and dietary supplements, such as medicinal herbs. Keep a list of all drugs being taken. Periodically discuss this list with the doctor or pharmacist. Keep a list of all disorders. Periodically discuss this list with the doctor. Select a pharmacy that provides comprehensive services (including checking for possible interactions) and that maintains a complete drug profile for each person. Have all prescriptions dispensed in this pharmacy. Learn about the purpose and actions of all drugs prescribed. Learn about the possible side effects of the drugs. Learn how to take the drugs, what time of day they should be taken, and whether they can be taken during the same time period as other drugs. Review the use of over-the-counter drugs with the pharmacist. Discuss any disorders present and any prescription drugs being taken. Take drugs as instructed. Report to the doctor or pharmacist any symptoms that might be related to the use of a drug. If seeing more than one doctor, make sure each doctor knows all the drugs being taken. Acid-blocking drugs, such as histamine-2 (H2) blockers and proton pump inhibitors, raise the pH of the stomach and decrease absorption of some drugs, such asketoconazole, a drug for fungal infections. Many drugs are broken down and inactivated (metabolized) by certain enzymes in the liver. Some drugs affect these liver enzymes, either increasing or decreasing their activity, and may cause another drug to be inactivated more quickly or more slowly than usual. For example, by increasing the activity of liver enzymes, barbiturates such asphenobarbitalcause the anticoagulantwarfarinto be inactivated more quickly and thus to be less effective when taken during the same time period. Conversely, by decreasing the activity of the enzyme system, drugs such aserythromycinandciprofloxacincan increase the activity ofwarfarin, risking bleeding. When drugs that affect liver enzymes are used in people takingwarfarin, doctors monitor the people more closely and adjust the dose ofwarfarinto compensate for this effect. Thewarfarindose is adjusted again when other drugs are stopped. Many other drugs affect liver enzymes. Chemicals in cigarette smoke can increase the activity of some liver enzymes. As a result, smoking decreases the effectiveness of some drugs, includingtheophylline(a drug that widens the airways called a bronchodilator). Some drugs affect the rate at which the kidneys excrete another drug. For example, large doses of vitamin C increase the urine's acidity and thus may change the rate of excretion and activity of certain drugs. For example, the rate of excretion may be decreased for acidic drugs such asaspirinbut may be increased for basic drugs such aspseudoephedrine. Because there are so many drug interactions, many doctors and pharmacists reduce the risk of problems by checking reference books and computer software programs when prescribing or dispensing prescriptions for additional drugs. In most pharmacies, drug orders and prescriptions are reviewed using a computer system that automatically checks for drug interactions. 