When a particular drug is taken by millions, some people may not respond in a predictable way, even though the drug has been tested.
A patient may also acquire a tolerance for a certain drug, which means the patient has to ______________________. Tolerance may lead to habituation, in which the person becomes so dependent on the drug that he or she becomes addicted to it. _________________________when the drug is taken away. Finally, drugs often have unwanted side effects. This usually causes only minor discomfort,____________________. Certain drugs, however, can produce serious adverse reactions.
