Millions of consumers are using the Internet to get health information. And thousands of web sites are offering health information. Some of those sites are reliable and up-to-date; some are not. How can you tell the good from the bad? Some websites that sell medicine can be not state-licensed pharmacies or aren't pharmacies at all; or may give a diagnosis that is not correct and sell medicine that is not right for you or your condition; or won't protect your personal information. Make sure the site requires a prescription and has a pharmacist available for questions. Buying your medicine online can be easy. Just make sure you do it safely.
Drug interactions may make your drug less effective, cause unexpected side effects, or increase the action of a particular drug. Some drug interactions can even be harmful to you. Reading the label every time you use a nonprescription or prescription drug and taking the time to learn about drug interactions may be critical to your health. You can reduce the risk of potentially harmful drug interactions and side effects with a little bit of knowledge and common sense. 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. The most important enzymes in the liver that metabolize drugs are called the cytochrome P450 family of enzymes. These enzymes break down drugs when they pass through the liver or small intestine. Not everything that happens in a test tube will become meaningful in humans, though. Results from these test-tube studies can tell us whether need to do further testing in people to find out if an interaction is clinically significant. 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. 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. Some antibiotics, such as rifampin, can lower the effectiveness of birth control pills. Sildenafil, the active ingredient in the erectile dysfunction drug Viagra, should not be taken with nitrates for heart treatment because of the potential for dangerously low blood pressure. Drug interactions with food and beverages, for example, taking quinolone antibiotics such as ciprofloxacin with food and drinks such as colas, coffee, and chocolate that contain caffeine may cause excitability and nervousness. There can be a potentially fatal increase in blood pressure if food containing tyramine is eaten when taking monoamine oxidase inhibitors, drugs that treat mood disorders. Examples of food with tyramine are cheese and soy sauce. Grapefruit juice should not be taken with certain blood pressure-lowering drugs or cyclosporine for the prevention of organ transplant rejection. Alcohol should not be taken with pain relievers such as Tylenol (acetaminophen) or ibuprofen because of the increased risk of liver damage or stomach bleeding.

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