Medicines can enter the body in many different ways, including through an inhaler, a skin patch, a pill or a hypodermic needle. As drugs make their way through the body, many steps happen along the way. Understanding how medicines work in your body can help you learn why it is important to use medicines safely and effectively. In this section on taking medicines, we’ll focus on medicines you take by mouth, since those are the most common.
When you take medicines by mouth, they move through the digestive tract and are taken up by internal organs like the stomach and small intestine. Often, they are then sent to the liver, where they might be chemically altered. Finally, they are released into the bloodstream.
As the bloodstream carries medicines throughout the body, the drugs can interact with many tissues and organs. Side effects can occur if a drug has unintended effects anywhere in the body.
Just as it does with food, the body tries to chemically break down medicines as soon as they enter the body. Most drugs taken by mouth enter the stomach or small intestine and then are sent to the liver.
The liver contains protein molecules called enzymes that chemically modify drugs and other non-food substances. The chemical alteration of a medicine by the body is called drug metabolism.
Often, when a drug is metabolized by the body, it is converted into products called metabolites. These metabolites are not usually as strong as the original drug, but sometimes they can have effects that are stronger than the original drug. For example, codeine in the prescription pain killer Tylenol#3 becomes fully active only after the medicine is metabolized in the liver.
Because most drugs and other “foreign” substances are broken down in the liver, scientists refer to the liver as a "detoxifying" organ. As such, the liver can be prone to damage caused by too much medicine in the body.
Drug metabolites often return to the liver and are chemically altered once again before they exit the body.
After a drug’s metabolites have circulated in the bloodstream, where they work as medicine, the body eliminates them the same way it eliminates other wastes—in the urine or feces. Age-related changes in kidney function can have significant effects on how fast a drug is eliminated from the body.
While everyone needs to be careful when taking a medicine, older adults frequently take more than one medication at a time. Medicines can interact with each other in unexpected ways, so anyone taking several medications at the same time should be extra careful. Also, as the body ages, its ability to absorb foods and drugs changes.
As people age, the body's ability to break down substances can decrease. Because older people may not be able to metabolize drugs as well as they once did, they might need smaller doses of medicine per pound of body weight than young or middle-aged adults do.
All medicines have risks as well as benefits. The benefits of medicines are that they can improve your health and well-being by doing what they were designed for, like treating a disease, curing infection, or relieving pain. The risks are the chances that something unwanted or unexpected will happen when you use medicines. Unwanted or unexpected symptoms or feelings that occur when you take medicine are called side effects.
Side effects can be relatively minor, such as a headache or a dry mouth. They can also be life-threatening, such as severe bleeding or irreversible damage to the liver or kidneys.
Stomach upset, including diarrhea or constipation, is a side effect common to many medications. Often, this side effect can be lessened by taking the drug with meals. Always check with your doctor, nurse, or pharmacist to see if you should take a particular medication with food.
Here are some more tips to help you avoid side effects.
You should always be sure to tell your doctor and/or pharmacist about any and all medications that you take every day or even once in a while. Be sure to include products like pain relievers, antacids, alcohol, herbal remedies, food supplements, vitamins and other substances you might not think are medicines.
Unwanted effects can occur when any substance interacts, or interferes with, another one. These chemical interactions change the way your body handles one or both substances.
In some cases, the overall effect of an interaction is greater than desired. Combining aspirin with blood-thinning drugs such as Coumadin®, also called warfarin, can cause serious bleeding. Mixing Viagra®, also called sildenafil, and the heart drug nitroglycerin can cause blood pressure to plunge to dangerously low levels.
Even if a product is not called a drug, your body handles it the same way it handles drugs. Some herbal and other substances can interact in potentially dangerous ways with prescription drugs or other over-the-counter products.
Some foods and beverages are known to interact with certain drugs. For example, a single glass of grapefruit juice can raise the level of some medications in the blood. This can occur with several types of drugs commonly used to treat heart conditions. Years ago, scientists discovered this "grapefruit juice effect" by luck, after giving volunteers grapefruit juice to mask the taste of a medicine.
Nearly a decade later, researchers figured out that grapefruit juice blunts the effects of an enzyme that breaks down drugs. This leads to higher levels of medicine remaining in the blood, which can cause health problems. Be sure to ask your doctor or pharmacist if it is safe to consume foods or beverages that contain grapefruit with the medication you are taking. You may still be able to enjoy grapefruit or its juice if you consume it at a different time of day than when you take medicine. Your doctor or pharmacist can advise you.
Some drugs or foods can also prevent other drugs from working properly. For example, calcium-rich dairy products or certain antacids can prevent antibiotics from being properly absorbed into the bloodstream. Ginkgo biloba can reduce the effectiveness of blood-thinning medications and raise the risk for serious complications such as stroke.
The medications a doctor prescribes for you are called prescription drugs. You can only pick them up at a pharmacy. Medicines you can get without a doctor's prescription, which you can buy at a grocery or convenience store, are called over-the-counter drugs. It is important to remember that over-the-counter products include many different substances such as vitamins and minerals, herbal and dietary supplements, laxatives, cold medicines, and antacids. Any of these can interact with each other to cause unexpected or unwanted effects.
Prescription and over-the-counter medicines almost always contain several ingredients. Check the labels of your medicines before you start taking them to ensure you are not allergic to any of the ingredients. Make sure your doctor and pharmacist have an up-to-date list of your allergies so they don’t give you a medicine that contains something you are allergic to.
Some of the ingredients in a medicine are not directly involved in its main job. These are called inactive ingredients. Examples of inactive ingredients include the substances that give a lozenge color or flavor or ingredients that ensure the drug within a capsule gets released at a controlled rate.
The active ingredients in medicines are the chemical compounds that work with your body to treat your condition or bring relief of your symptoms. Learn which active ingredients are in the prescription and over-the-counter medicines you are taking.
For example, over-the-counter pain relievers usually contain one or more of the active ingredients below:
Some medicines are designed to treat more than one condition, so they have more than one active ingredient. Many cold and flu remedies are an example of this. They might contain a combination of ingredients to sooth a sore throat, calm a cough, stop up a runny nose and bring down a fever.
Don't take more than one medicine that contains the same active ingredient(s). For example, if your cough syrup contains acetaminophen, don’t take a pain reliever that contains acetaminophen while you are using the cough syrup. Taking more than one medicine that has the same active ingredient could result in getting too much of that ingredient. Too much of any one ingredient might damage your liver or lead to other serious health problems.
Always read the labels on the over-the-counter products you are taking to find out whether the active ingredients have side effects. For example, antihistamines can cause drowsiness. Caffeine, which is present in some over-the-counter medicines, can interact with certain drugs or can cause problems with underlying conditions such as high blood pressure.
Older people as a group tend to have more long-term, chronic illnesses such as arthritis, diabetes, high blood pressure and heart disease than any other age group. Because they may have a number of health problems or issues at the same time, it is common for older people to take many different drugs. Here are some tips on how to take medicines safely and get the best results from them.
If your doctor prescribes a medication for your condition, try to find out as much about it as you can, including how to take it properly. Ask the following questions and write down the answers before leaving the doctor's office.
Ask your doctor, pharmacist, or nurse about the right way to take any medicine before you start to use it. Ask questions when you don't know the meaning of a word, or when instructions aren't clear. Here are some specific questions to ask.
Taking different medicines is not always easy to do properly. It may be hard to remember what each medicine is for, and how and when you should take each one. Here are some helpful hints about taking medicines.
Keeping track of your medicines is very important. Making sure that they are stored properly, that they have not expired when you take them, and that prescriptions are refilled requires time and attention.
Also, taking many different medications at the same time is difficult. It can be hard to remember what each drug is for, when you should take it, and how you should take it. This is especially true for people with memory problems. However, there are simple strategies you can use to help you manage your medicines wisely.
Finally, the pharmacist is a good source of information about your medicines. In addition to answering questions and helping you select non-prescription medications, your pharmacist keeps records of all the prescriptions you get filled at that store.
Because the pharmacist keeps these records, it is a very good idea to have the same store fill your prescriptions whenever possible.
Be prepared in case of accidental poisoning involving medications or other substances. Call Poison Help at 1-800-222-1222 to speak with a poison expert at the poison center serving your area. The service is free and available 24 hours a day, 7 days a week, and calls are always free and confidential. Interpreter services are also available in 160 languages. Keep the number programmed in your home phone and mobile device.
For more information, visit the Poison Help website at www.poisonhelp.hrsa.gov
The Food and Drug Administration, or FDA, is the federal agency responsible for making sure that foods and cosmetics are safe, and that drugs and medical devices are safe and effective. Clinical trials are a key part of drug discovery and development, and the FDA requires that new drugs be tested in clinical trials before they are put on the market. A clinical trial is a research study to find out if a new drug or treatment is both safe and effective for people to use.
Clinical trials are sponsored or funded by pharmaceutical companies, federal agencies like the National Institutes of Health, foundations, individuals, and voluntary groups. Trials can take place in a variety of locations, such as hospitals, universities, doctors' offices, or community clinics.
Clinical trials are used to test new therapies and to compare existing drugs. Their goal is always see which medication or combination of medications is the safest or most effective for treating a particular ailment.
Both prescription drugs and over-the-counter drugs are tested in clinical trials before they become available to the public. However, according to a 1994 law, ingredients used in dietary supplements no longer have to be tested in clinical trials before they go on the market. Also, there are no regulations that govern the way these substances are manufactured.
Scientists usually do years of experiments in the laboratory and in animals before they can even consider testing an experimental medication in people. Most of this early research occurs at universities and medical centers across the country and much of it is funded by the National Institutes of Health.
Most of the medicines tested in scientists' laboratories fail in laboratory or animal studies, and it can take years to bring a new medicine from the laboratory to your local pharmacy.
Developing drugs is a time-consuming and expensive process. Yet, clinical trials are the only way doctors can know for sure whether medicines are both safe and effective in people.
Enrolling in a clinical trial offers benefits and risks. If you choose to participate in a clinical trial, you may get therapies not yet available to most patients. Also, patients in clinical trials are watched very closely, and they typically benefit from a high standard of care.
Importantly, scientists who wish to test drugs in people must follow strict rules that are designed to protect those who volunteer to participate in clinical trials. Special groups called Institutional Review Boards, or IRBs, evaluate all proposed research that involves human volunteers or patients.
The goal of an IRB is to make sure that the risks to humans are minimized and that these risks are reasonable compared to the knowledge researchers expect to gain by doing the study. Clinical studies cannot go forward without IRB approval.
Testing potential new drugs in people is done through a process known as clinical trials. A clinical trial is a research study with people to find out if a new drug or treatment is both safe and effective. This type of medical research has led to treatments for many diseases, such as Hodgkin's lymphoma, arthritis, heart disease, and childhood leukemia.
People who participate in clinical studies must provide informed consent. That means they need to be told (informed) about the goals, procedures, and potential risks of the trial. They must agree (consent) to participate by signing a form, required by law, that says they understand the possible risks and benefits of the study.
Throughout a study, patients are kept informed about anything that may affect their willingness to continue. Clinical trial patients may withdraw from a study at any time, even after signing the consent form.
Scientists conduct clinical trials in three steps, called phases I, II, and III. Each phase provides the answer to a different question about a potential new drug: Is it safe? Does it work? Is it better than the standard treatment?
Many phase II and phase III studies are randomized, meaning that patients are randomly assigned to get either the experimental drug, a standard treatment (if there is one) or a placebo (if there isn’t a standard treatment). A placebo often comes in the form of a "dummy" pill or injection that doesn’t contain any medicine. The use of placebos helps researchers compare the effects of a given treatment against no treatment.
Usually, phase II and phase III studies are "double-blinded" -- neither the patients nor the researchers know who is getting the experimental drug. This helps to prevent bias on the part of the researcher or the patient.
Finally, once a new drug has completed phase III testing, a pharmaceutical company can request approval from the Food and Drug Administration to market the drug. Once a drug goes on the market, it undergoes a period called phase IV, or "post-market surveillance."
Just after a new drug becomes available, patients and doctors may notice uncommon and unexpected problems with the medicine. This is because rare problems, which range from mild to severe side effects, can only surface when huge numbers of people begin taking the medication.
To find out more about participating in a clinical study, talk to your doctor or search on-line for the clinical trials that are available. For more information visit http://nihseniorhealth.gov/
participatinginclinicaltrials/toc.html or the federal Web site: ClinicalTrials.gov.
Studies have shown that bad reactions to properly prescribed medicines cause a number of hospitalizations each year. Researchers believe that many of these errors show that when it comes to taking medicines, "one size does not fit all."
For example, allergy medicines simply don't work for everyone who takes them. For some people, taking the standard dosage of a prescription pain reliever such as codeine offers no pain relief, and can even cause side effects that are uncomfortable or life-threatening.
As the body ages, fat and muscle content change, affecting how the body absorbs and processes drugs. Many other factors -- exercise habits, diet, and general state of health -- also influence how a person responds to medications.
Another key factor is heredity -- the genes we inherit from our parents and other ancestors. Genes can influence the way people respond to many types of medicines, such as Tylenol#3®, which is acetaminophen plus codeine; antidepressants like Prozac®, also called fluoxetine; and many blood pressure and asthma medicines.
Your genes determine the shape and function of your proteins. As drugs travel through the body, they interact with dozens of proteins.
Everyone’s genes are slightly different, so everyone’s proteins are different. Variations in some proteins can affect the way we respond to medicines. Such proteins include those that help the body absorb, metabolize, or eliminate drugs.
Many scientists around the country are conducting research to understand how genes affect the way people respond to medicines. This type of research is called pharmacogenomics.
As pharmacogenomics research progresses, it will become increasingly important to identify all the possible variations in genes that play a role in drug response. To identify which versions of these genes a person has, researchers examine DNA from that person. An easy, painless, and risk-free way to obtain DNA is from mouth cells that stick to a cotton swab rubbed on the inside of a volunteer's cheek.
Uncovering differences in people's genetic backgrounds will help doctors prescribe the right medicine in the right amount for each person, making medicines more safe and effective for everyone.
Scientists will also better understand the role that genes play in causing or contributing to diseases including cancer, heart disease, diabetes, depression, and many others. Research in pharmacogenomics will help scientists make future medicines as safe and effective as possible.
Source: NIHSeniorHealth, NIH