TRI DUC ENGLISH - How Drugs Are Studied TRI DUC ENGLISH Reading Practice: How Drugs Are Studied A It takes years, and sometimes decades, for a drug to move from the theoretical stage to the pharmacy shelf. Of the thousands of drugs under investigation at any one time, only a small fraction will produce the desired result without unacceptable side effects. B First, scientists target a step in the disease process where they believe a drug can have an effect. Then they manufacture compounds or take them from organisms such as viruses and fungi and test them in laboratory cultures. Once scientists isolate a chemical that produces a desirable effect, they analyze its structure and alter it as necessary to enhance the outcome. C The next step involves testing the drug in animals. Scientists look at how much drug is absorbed into the bloodstream, how it distributes to different organs, how quickly it is excreted or leaves the body, and whether it has any toxic effects or by-products. Researchers usually test at least two animal species because the same drug may affect species differently. D If a chemical passes laboratory and animal testing and is deemed appropriate to analyze in human volunteers, it is ready for clinical trials. Researchers follow a protocol that describes who may participate in the study, tests and procedures to follow, the length of the study, and outcomes to be measured. Drug trials may focus on treating a disease, preventing a disease from occurring or recurring, or enhancing the quality of life for people living with incurable, chronic conditions. E There are four phases of clinical trials; the first three phases study whether the drug is effective and can be safely administered to patients, and the fourth phase evaluates long-term safety and use once a drug is on the market. F Phase I clinical trials test a drug in small groups of healthy volunteers (fewer than 100) to ascertain its safety and the appropriate dose range. These studies last for six months to one year. G Phase II clinical trials test several hundred volunteers to de...