1.  Washout Periods - You should always obey washout periods.  The minimum washout period for all clinics in the US for any study you have dosed in, (regardless of whether or not you completed the study) is 30 days.  Some studies will have longer washout periods.  Radiolabel studies usually have a 1 year washout before you can do another radiolabel study. 

2.  Participate in only one study at a time - You should only be enrolled and participating in one study at a time.  You should never participate in more than one study at a time.  Interactions between multiple study medications can have unknown reactions and side-effects that can be life-threatening or even fatal. 

3.  Follow all procedures of the study - You should follow all procedures, cutoffs and guidelines of the study as outlined in the informed consent form.  When you sign the informed consent form, you are agreeing to comply.  You are being paid to do so and failure to comply is a breech of contract.  If you are found to be in violation of procedures, cutoffs and guidelines, you can be removed from a study without pay and not allowed to participate in future studies.  While it may not seem necessary to eat all of your food or urinate at the urine monitoring station, if it's part of the study, then you must comply.  All procedures, cutoffs and guidelines are there to ensure the integrity of the study results and if people are not following these, then the results of the study may be skewed which in turn can affect the ability and timeliness of the study drug from reaching it's targeted patients. 

4.  Follow all rules of the clinic - You should follow all rules of the clinic.  Again, when you sign up for a study, you also sign a form agreeing to follow the rules of the clinic.  Failure to follow these rules and can result in monetary fines and if your infractions are serious enough, you can be removed from a study without pay and not allowed to participate in future studies.  While it may seem silly to have to follow rules like bedtimes, sharing the TV and not sneaking in camera phones, if the clinic has rules, then you must follow them.  Again, you are being paid to do so.  If you break the law and run a red light and you are caught, you will be fined.  The same with most clinics. 

5.  Compete all parts of the study - Once you sign up to screen for a study, you should be committed to follow through with the study.  Once you screen for a study, you should make every effort to check in.  It is inappropriate to cancel a study once you've screened just because a better study comes out.  If a study doesn't have enough volunteers checking in, it may be postponed or cancelled.  How would you feel if a study that you really wanted to do got cancelled because a bunch of people quit at the last minute?  Okay then.  it's a two way street.  Once you start the study, you should finish all parts including multiple stays, out-patients and follow-up phone calls.