<div class="FTQUOTE"><begin quote><i>Originally posted by: <b>chroma7</b></i> most drugs get approved in phase 4. 770 got approved in phase 3. p.</end quote>
No, all drugs are required to go through 3 phases of clinical trials.
From the FDA's website. As you can see, Phase IV is post-marketing study aka, after the drug has been FDA approved and hit the market:
<a class="header2" name="Q19"></a>What are the phases of clinical trials?<span>Clinical trials are conducted in phases. The trials at each phase have a different purpose and help scientists answer different questions:<span>In<a href="http://clinicaltrials.gov/ct2/info/glossary#phasel">Phase I trials</a><span>, researchers test an experimental drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.<span>In<a href="http://clinicaltrials.gov/ct2/info/glossary#phasell">Phase II trials</a><span>, the experimental study drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.<span>In<a href="http://clinicaltrials.gov/ct2/info/glossary#phaselll">Phase III trials</a><span>, the experimental study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the experimental drug or treatment to be used safely.<span>In<a href="http://clinicaltrials.gov/ct2/info/glossary#phaselv">Phase IV trials</a><span>, post marketing studies delineate additional information including the drug's risks, benefits, and optimal use.
Source:<a href="http://clinicaltrials.gov/ct2/info/understand">http://clinicaltrials.gov/ct2/info/understand</a>