The Internet has changed the way we live, work and shop. The growth of the Internet has made it possible to compare prices and buy products without ever leaving home. But when it comes to buying medicine online, it is important to be very careful. Some websites sell medicine that may not be safe to use and could put your health at risk.

First, it's important to carefully consider the source of information and then to discuss the information you find with your health care professional. These questions and answers can help you determine whether the health information you find on the Internet or receive by e-mail from a Web site is likely to be reliable.

Make sure the site requires a prescription and has a pharmacist available for questions.

For example, every time you get into a car, there are risks---the possibility that unwanted or unexpected things could happen. You could have an accident, causing costly damage to your car, or injury to yourself or a loved one. But there are also benefits to riding in a car: you can travel farther and faster than walking, bring home more groceries from the store, and travel in cold or wet weather in greater comfort.

To obtain the benefits of riding in a car, you think through the risks. You consider the condition of your car and the road, for instance, before deciding to make that trip to the store.

For example, if facing a life-threatening illness, you might choose to accept more risk in the hope of getting the benefits of a cure or living a longer life. On the other hand, if you are facing a minor illness, you might decide that you want to take very little risk.

To lower the risks and obtain the full benefits of medicines you need a)talk with your doctor, pharmacist, or other health care professionals; b)know your medicines--prescription and over-the-counter; c)read the label and follow directions; d)avoid interactions; e)monitor your medicines' effects--and the effects of other products that you use

You need keep an up-to-date, written list of ALL of the medicines (prescription and over-the-counter) and dietary supplements, including vitamins and herbals, that you use--even those you only use occasionally.

Read and follow the directions on the label and the directions from your doctor, pharmacist, or other health care professional. If you stop the medicine or want to use the medicine differently than directed, consult with your health care professional.

Ask your doctor if there is anything you can do to minimize side effects, such as eating before you take a medicine to reduce stomach upset.

You always have to pay attention to how you are feeling; note any changes. Write down the changes so that you can remember to tell your doctor, pharmacist, or other health care professional.

You have to know what to do if you experience side effects and when to notify your doctor, and know when you should notice an improvement and when to report back.

There are more opportunities today than ever before to learn about your health and to take better care of yourself. It is also more important than ever to know about the medicines you take.

Early in a drug's development, companies conduct research to detect or predict potential interactions between drugs. Experts evaluate the drug-interaction studies as part of assessing a drug's safety.

When a drug is taken orally, it usually travels from the stomach to the liver, where it can be metabolized-the process of breaking down and removing chemicals from the body. Enzymes are complex proteins that act as catalysts in starting or speeding up chemical reactions. They cause a specific chemical change in other substances without being changed themselves.

It used to be that the only way to test for drug interactions was in people. Now drug companies can take five test tubes with the five major pathways for metabolism and put their drugs in to see whether it's metabolized by CYP450. This allows to generate a list of possible interactions based on their findings.

This phase of research in test tubes, known as in vitro studies, allows researchers to perform drug-interaction studies in labs by testing a drug with other drugs that have the same route. This has made the research faster and more accurate. If two drugs go through the same enzyme, the presence of one drug can prevent the metabolism of the other. So this allows you to look at the worst-case scenarios and ask: 'What if we put this drug with that one, knowing that they have the same route?'"

Three phases of clinical trials in humans must happen before a drug can be marketed. Phase 1 studies focus on a drug's side effects and how the drug is metabolized and eliminated from the body. Phase 2 studies focus on a drug's effectiveness. And Phase 3 studies gather more information on safety and effectiveness, which includes using the drug in combination with other drugs.

Researchers say there are several important variables that affect individual differences in how drugs are metabolized, including race, gender, age, and health conditions. For example, people with kidney or liver disease don't eliminate drugs from their system as well as people who are healthy. Very young children and older people have slower drug metabolism than others, and women may metabolize drugs differently than men in some cases.

The large number of drugs on the market, combined with the common use of multiple medications, makes the risk for drug interactions significant. Consumers need to tell doctors what they're taking and ask questions, and health professionals could do a better job at trying to get the information they want.

So rather than asking patients what medications they take, doctors should make the questions specific: "Are you taking any over-the-counter medication? Are you taking any herbal treatments or vitamins?"

Drug interactions with other drugs includes both prescription and over-the-counter medicines. Tricyclic antidepressants such as Elavil (amitriptyline) and Pamelor (nortriptyline) can interfere with blood pressure-lowering Catapres (clonidine). Taking the antibiotic Cipro (ciprofloxacin) with antacids lowers Cipro's effectiveness.

Drug interactions with dietary supplements includes herbs and vitamins, which can interact with drug-metabolizing enzymes. St. John's wort is an herb commonly used by people with cancer to improve mood, but research has shown it interferes with the metabolism of irinotecan, a standard chemotherapy treatment. Vitamin K (in dietary supplements or food) produces blood-clotting substances that may reduce the effectiveness of blood-thinning medicines like warfarin.

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