Thursday, May 10, 2012

Peak and Trough Tests for Methadone Maintenance Patients -- What are They Good For?


If you're a methadone patient you may or may not know about peak and trough testing.  Not knowing about P&T's might mean that they aren't widely used at your clinic, and that's probably a good thing.  What follows is a very, very broad explanation of what peak and trough testing is, and what it is used for.

Clinics usually use Peak and trough (P&T) testing when a patient requests an increase of their methadone dose above and beyond what the clinic considers "reasonable".  Basically, P&T tests measure the level of methadone in your blood.  Your blood is first tested immediately before you dose.  This is when the amount of methadone in your body would be lowest, the so-called "trough" part of the test.  Then your blood is tested approximately three hours after you dose, when the level of methadone in your body would be highest.  This is the "peak" measurement of the test.  The doctor then looks at the numbers from each part of the tests.  If the level of methadone measured at the trough is too low, then your dose might be too low.  If the doctor thinks the level measured at the peak is too high, then your request for an increase in your dose will be refused, and it may actually be cut.

There are two problems with this test.  The P&T test can be untrustworthy due to the makeup of methadone manufactured in the United States.  Note: things get pretty scientific here.  Methadone manufactured in the U.S, is composed of two different parts called "isomers".  The isomers are mirror images of each other, like your left and right hand.  However, one of the isomers is active, meaning that it produces the effects methadone is known for, and one of the isomers is inactive.  The inactive isomer does not have any effect on the body.  The P&T test measures both isomers without distinguishing between the active one and the inactive one.  The methadone levels in your body could be made up of more inactive isomers than active ones.  So while the test may show that you have adequate levels of methadone in your body, those levels could be primarily composed of the inactive isomer,  which has no effect on you.   In a nutshell, the P&T test can show that your methadone levels are adequate, when in reality you are need a higher dose.  For these reasons, P&T tests can be mistaken at best, and at worst totally unreliable.  Doctors should listen to their patients descriptions of how they feel, and base their dosing decisions primarily on that.  A patient's complaint that he still has cravings, or is in withdrawal, is better evidence that he needs an increase than a P&T test.

Many patients are afraid to ask for a dose increase, fearing that their clinic will slash their dose if the P&T shows that their methadone levels are too high.  This is a major problem.  Study after study proves that patients on higher methadone doses have better treatment outcomes.  These patients use fewer opiates and stay in treatment longer.  Furthermore, the patients in these studies are often on doses that most people in the treatment community consider far too low.  For instance, the "high dose" in the second study was only fifty milligrams.  Although the optimum methadone dose varies by patient to patient, most clinicians agree that a patient should be on at least sixty milligrams of methadone a day in order to reduce cravings, stop withdrawal, and block the effects of additional opiates.

So, can P&T testing ever be useful?  Yes, as long as it is used in conjunction with listening to the patient.  Sometimes patients don't adequately express how their dose makes them feel, and a P&T test can help decide if they are on the right dose.  P&T tests can determine whether someone should split dose, instead of taking all of their methadone at one point in the day.  However, it is medically unethical  to use P&T tests to arbitrarily deny dose increases.

4 comments:

  • Zac Talbott says:
    March 2, 2013 at 3:56 PM

    This is an article that ALL MMT patients should read... In the state of Tennessee (where I live) and the state of Georgia a P&T is required anytime a patient requests an increase that would result in a dosage higher than 120mg's/day. I agree that these tests can be useful if looked at as an indicator while taking into account the patient's own testimony, but it is CERTAINLY unethical (at the least) to use P&T tests to arbitrarily deny dose increases as the article attests. GREAT general info!! Thanks! :-)

  • Mari says:
    October 24, 2013 at 3:33 PM

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  • Julie says:
    November 14, 2013 at 4:09 PM

    Grey,
    It is true there are two isomers of metahone. It is not true your methadone level may reflect more of the inactive isomer. The isomers are always present in equal concentrations.

  • Scam Lackey says:
    March 3, 2014 at 4:57 PM

    Hey Julie...they are never in equal concentrations when they hit the body. Do a little more research. They have different actions in the body and are metabolized at different rates. The jury is still out on the differences. Some sources say one thing and some say the opposite.

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