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What Are Drug Interactions?

Every time you take more than one medicine or even mix it with several foods, beverages, or over-the-counter medications, you have a risk of a drug interaction. Most drug interactions are not significant, but a few are, it is vital to know the possible outcomes of interactions before you take any medication.

Drug-to-drug interactions

The most common type of interaction occurs between the two drugs. The more medicines you take, the higher the risks of one drug interacting with others. Drug to drug interactions decreases the effectiveness of your medications, may increase mild to severe unwanted side effects, or increase the blood levels and toxicity of the drug. For example, if you are simultaneously taking pain medication like Norco, and a sedating antihistamine, such as Benadryl, you will have additive drowsiness as it is a side effect associated with most the medicines.

Drug-to-food interactions

You must have seen the warning on your medicine label saying, “avoid grapefruit juice.” It may seem odd to you, but some medications interact with food or beverages. For example, the juice of grapefruit can lower enzyme levels in your liver that are responsible for breaking down the medicine. The interacting drug may have increased blood levels that lead to toxicity. These interactions can occur with frequently used statins to lower cholesterol levels, like lovastatin, atorvastatin, or simvastatin. The effects of interaction can be muscle pain or severe muscle injury known as rhabdomyolysis.

Drug-to-disease interactions

Medicines did not always interact with other drugs, foods, or beverages. Your medical condition can also affect your medication. Some medical conditions interact with medicines and change or modify the way they work. For example, oral decongestants, over-the-counter pseudoephedrine like Sudafed or phenylephrine like Sudafed PE increases blood pressure and can be life-threatening if you already have high blood pressure.

How the interactions of drugs occur?

Drug interactions occur in specific ways:

Pharmacodynamic interaction

This interaction occurs when two drugs taken together act at the similar or same receptor site and lead to a more significant additive or synergistic effect or a decreased antagonist effect. For example, when haloperidol, anti-psychotic medication for treating schizophrenia and chlorpromazine, useful to prevent nausea and vomiting, are taken together, they may have a higher risk of causing severe fatal, irregular heart rhythm.

Pharmacokinetic interaction

This interaction occurs when one drug affects the distribution, absorption, excretion, or metabolism of the other drug. Some examples will help you understand these complicated mechanisms:

  • Distribution: Interactions that bind protein can occur when two or more protein-bound drugs compete for binding sites on plasma proteins. For example, an interaction between warfarin, a blood thinner used to prevent blood clots and fenofibric acid or Trilipix, a medicine to lower cholesterol and triglycerides in your blood. Warfarin’s effects increase by fenofibric acid and cause you easily bleed more.
  • Absorption: Some drugs alter the process of absorption of another drug into the bloodstream. One example here is calcium, as it can bind with some medicines and block their absorption. It would be best if you did not take calcium carbonate, namely Maalox, Tums, or others with the HIV treatment dolutegravir, Trivicay, as calcium can reduce the amount of dolutegravir absorbed into your bloodstream, thus reducing its efficacy and effectiveness in the treatment of HIV infection. Take dolutegravir at least two hours prior to or 6 hours after taking medicines containing calcium or other minerals to prevent their interaction. In the same way, you should not take many drugs with milk or dairy products as they will bind with calcium. Drugs affecting intestine or stomach motility, natural flora, or pH can also lead to drug interactions.
  • Excretion: Several nonsteroidal anti-inflammatory drugs or NSAIDs such as indomethacin can lower kidney functions and affect the excretion of lithium, useful in the treatment of a bipolar disorder. It would be best if you had a dose adjustment or frequent dose monitoring by your health care expert to use both medicines together safely.
  • Metabolism: Medicines usually leaves our body as either the parent or unchanged drug or as a metabolite of the drug. Liver enzymes often the CYP450 enzymes are mainly responsible for the break down of medications for elimination from your body. However, the levels of enzymes may go up and down to affect the break down of drugs. For instance, taking diltiazem, a blood pressure medication with simvastatin, a medication to lower cholesterol, elevates the blood levels, and adverse effects of simvastatin. High simvastatin blood levels lead to severe liver and muscle effects.

Why is it so important to know about drug interactions?

It is essential to check the drug interactions of your medicines as they can:

  • Affect the working of your medication by changing its blood levels
  • Increase the risk for side effects and toxicity
  • Worsen your medical condition

Knowing about your medicine’s interaction before it actually takes place can drastically decrease the chance of risks associated with it. Generally, your doctor or pharmacist will do this if you are taking prescription medications, but it’s always better to double-check and learn about the interactions yourself. In case you are using over-the-counter medicines, including multi-vitamins, food or herbal supplements, etc. you need to be sure to know all the interactions of these products with your prescription medications and other drugs too. Ask your health care expert for some advice if you have any confusion due to the medical jargon.

Drug interactions also contribute to the cost of health care because a severe drug interaction may result in injury, medical conditions, hospitalization, and even death in serious cases.

All drug interactions are not harmful in nature. Some medicines may get better absorbed if you take them with food, or they may have some favorable blood levels when taken with other medications that affect metabolic enzymes.

How often drug interactions occur?

Significant life-threatening drug interactions are not frequent, but they are of serious concern. The interactions listed on medication labeling are often theoretical based on the pharmacology of a drug. However, if you avoid a possible drug interaction by selecting a different medicine or an adjusted dose of a medicine, then that is always the best way to handle your medications and their interactions.

It often occurs that people do not know about the interaction of two or more drugs, so it is important to see the status of your drug interaction with every new drug. In fact, some medicines can also be affected by stopping any other medication. It would help if you were proactive for your own health, check all the drug interactions, and discuss all the concerns with your health care provider to save yourself from the chances of any life-threatening risks.

Example of drug interaction along with alcohol can be understood through this post: Tramadol and Alcohol Reaction

How often a drug interaction occurs depends upon several factors, such as:

  • Number of medications you are taking
  • Age, liver, and kidney functioning
  • Your medical conditions
  • Your diet and possible drug interactions
  • Your genetics and the metabolic enzymes in your body

What are the other factors that can cause interactions?

You should not forget that caffeine, alcohol, and illegal drugs of abuse lead to severe drug interactions. For example, if you take pain medication such as Norco, contain the combination of hydrocodone and acetaminophen, with alcohol, it can cause additive sedating effects such as drowsiness, may result in decreased breathing rate, and at larger doses may cause intoxication to the liver due to the combination of alcohol and acetaminophen.

Taking medicine not prescribed to you can be dangerous, as it can lead to unexpected drug interactions. Avoid taking medicines prescribed to someone else or buying medicines without a prescription.

How to check for the interactions of drugs?

Communicate with your health care provider to help prevent drug interactions. Keep a list of all your medications, including prescription medicines, over-the-counter products, herbals, vitamin, or other health supplements, and also your medical conditions. Whenever you visit a doctor or pharmacist, please share this list with them at each visit so that they can quickly screen for possible drug interactions.

Read prescription information, medication guide, drug facts label, and warning label provided with each prescription and over-the-counter product. Information labeling may also change as researchers learn new information about the medicines, so it is important to review all the drug-related information frequently.

You should ask your health care provider about the latest information and news regarding your medications. However, you can also use online drug interactions checking tools to learn more about all the potential drug interactions. These tools will explain all about the interaction, its occurrence, it’s level of significance, and a suggested course of action. They display all the interaction between your drug and other drugs, food or beverages, additional products, and medical conditions.

What to do if I find a drug interaction?

Don’t worry. Always remember that most drug interactions are usually preventable with some proactive efforts. So, if you discover that you are at risk for potential drug interaction, call your health care provider as soon as you can. They understand the significance of interactions and will be able to tell you the best next steps for you. However, it is not advisable to stop your medicines or change their dosing without consulting your doctor or pharmacist first.

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