What Is Drug Interaction

What are drug interaction?

Anytime you take more than one medication, or even mix it with certain foods, beverages, or over-the-counter drugs, you are at risk of a drug interaction. Most drug interactions are not harmful, but because a handful are, it is vital to understand the probable outcome before you take your drugs.

Drug-drug interactions - These are the most common type of drug interaction. The more prescriptions you take, the greater the possibility for your drug reacting with another medicine. Drug-drug interactions can lower how well your prescriptions work, may raise minor or significant unanticipated side effects, or even increase the blood level and possible toxicity of a certain drug. For example, if you take a pain medicine, like Vicodin, and a sedating antihistamine, such as Benadryl, at the same time you will have an additional level of sleepiness as both medications induce this adverse effect.

Drug-food/beverage interactions - You have definitely seen the stickers on your prescription bottle to “avoid grapefruit juice” at one time or another. This may seem unusual, but certain drugs can interact with foods or beverages. For example, grapefruit juice can diminish the levels of enzymes in your liver responsible for breaking down drugs. Blood levels of an interacting medicine may rise, resulting to toxicity. This interaction can occur with the regularly used statins to decrease cholesterol, including atorvastatin, lovastatin, or simvastatin. The result can be muscle soreness, or even serious muscle injury known as rhabdomyolysis.

Drug-disease interactions - Drug interactions don't usually occur with simply other drugs or foods. Your existing medical condition can alter the way a medicine works, too. For example, over-the-counter oral decongestants like pseudoephedrine (Sudafed) or phenylephrine (Sudafed PE) may increase blood pressure and can be harmful if you have already high blood pressure.

How do medication interactions occur?

Drug interactions can occur in numerous ways:

1. A "pharmacodynamic interaction " occurs when two medications given simultaneously act at the same or comparable receptor location and contribute to a larger (additive or synergistic) effect or a lower (antagonist) effect. For example, when chlorpromazine, commonly used to assist prevent nausea and vomiting, and haloperidol, an antipsychotic medicine for schizophrenia, are administered together there may be an increased risk for producing a significant, possibly fatal abnormal heart rhythm.

2. A "pharmacokinetic interaction " may occur if one medicine affects another drug's absorption, distribution, metabolism, or excretion. Examples can help to clarify these sophisticated mechanisms:

• Absorption: Some medications can influence the absorption of another substance into your circulation. For example, calcium can bind with some drugs and inhibit absorption. The HIV medicine dolutegravir (Tivicay) should not be taken at the same time as calcium carbonate (Tums, Maalox, others), because it can lower the quantity of dolutegravir absorbed into the bloodstream and reduce its efficiency in treating HIV infection. Dolutegravir should be used 2 hours before or 6 hours after drugs that include calcium or other minerals to help prevent this interaction. In the same manner, many medicines cannot be taken with milk or dairy products because they will bind with the calcium. Drugs that influence stomach or intestine motility, pH, or natural flora can also lead to drug interactions.

• Distribution: Protein-binding interactions can arise when two or more highly protein-bound medicines compete for a limited number of binding sites on plasma proteins. One example of such interaction is between fenofibric acid (Trilipix), used to decrease cholesterol and triglycerides in the blood, and warfarin, a common blood thinner to help avoid clots. Fenofibric acid can exacerbate the effects of warfarin and cause you to bleed more easily.

• Metabolism: Drugs are normally removed from the body as either the unmodified (parent) substance or as a metabolite that has been transformed in some way. Enzymes in the liver, notably the CYP450 enzymes, are often responsible for breaking down medications for removal from the body. However, enzyme levels may go up or down and alter how medications are broken down. For example, using diltiazem (a blood pressure drug) with simvastatin (a treatment to decrease cholesterol) may boost the blood levels and side effects of simvastatin. Diltiazem can inhibit (block) the CYP450 3A4 enzymes needed for the breakdown (metabolism) of simvastatin. High blood levels of simvastatin might lead to significant liver and muscle adverse effects.

• Excretion: Some nonsteroidal antiinflammatory medicines (NSAIDs), such indomethacin, may lower kidney function and influence the excretion of lithium, a drug used for bipolar disorder. You may need a dose change or more frequent monitoring by your doctor to properly utilize both drugs together.

How often a drug interaction occurs, and your risk for a drug interaction, Also depends upon factors such as: Total amount of drugs you take Age, kidney and liver function Diet and probable medication interactions Medical conditions Metabolic enzymes in your body and your genetics

What should I do if I notice a drug interaction?

Remember that medication interactions are typically avoidable with your proactive efforts. However, if you realize you are at risk for a probable drug interaction, notify your doctor or pharmacist as immediately as you can. They will grasp the relevance of the contact, and will be able to offer the next best measures you should take. Do not stop your medicine without