[Code of Federal Regulations]
[Title 49, Volume 1]
[Revised as of October 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR40.137]

[Page 575]
 
                        TITLE 49--TRANSPORTATION
 
          Subtitle A--Office of the Secretary of Transportation
 
PART 40_PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING 
 
     Subpart G_Medical Review Officers and the Verification Process
 
Sec.  40.137  On what basis does the MRO verify test results involving 

marijuana, cocaine, amphetamines, or PCP?

    (a) As the MRO, you must verify a confirmed positive test result for 
marijuana, cocaine, amphetamines, and/or PCP unless the employee 
presents a legitimate medical explanation for the presence of the 
drug(s)/metabolite(s) in his or her system.
    (b) You must offer the employee an opportunity to present a 
legitimate medical explanation in all cases.
    (c) The employee has the burden of proof that a legitimate medical 
explanation exists. The employee must present information meeting this 
burden at the time of the verification interview. As the MRO, you have 
discretion to extend the time available to the employee for this purpose 
for up to five days before verifying the test result, if you determine 
that there is a reasonable basis to believe that the employee will be 
able to produce relevant evidence concerning a legitimate medical 
explanation within that time.
    (d) If you determine that there is a legitimate medical explanation, 
you must verify the test result as negative. Otherwise, you must verify 
the test result as positive.
    (e) In determining whether a legitimate medical explanation exists, 
you may consider the employee's use of a medication from a foreign 
country. You must exercise your professional judgment consistently with 
the following principles:
    (1) There can be a legitimate medical explanation only with respect 
to a substance that is obtained legally in a foreign country.
    (2) There can be a legitimate medical explanation only with respect 
to a substance that has a legitimate medical use. Use of a drug of abuse 
(e.g., heroin, PCP, marijuana) or any other substance (see Sec.  
40.151(f) and (g)) that cannot be viewed as having a legitimate medical 
use can never be the basis for a legitimate medical explanation, even if 
the substance is obtained legally in a foreign country.
    (3) Use of the substance can form the basis of a legitimate medical 
explanation only if it is used consistently with its proper and intended 
medical purpose.
    (4) Even if you find that there is a legitimate medical explanation 
under this paragraph (e) and verify a test negative, you may have a 
responsibility to raise fitness-for-duty considerations with the 
employer (see Sec.  40.327).