Methadone to Suboxone Conversion

From tonight’s keywords, a question about the potency of Suboxone in relation to methadone.  Remember that Suboxone is a ‘partial agonist’; this property is what allows the unique action of Suboxone in treating opiate dependence.  Opiate agonists like oxycodone, morphine, or heroin will have an increasing opiate effect as the dose is increased.  A graph of dose vs effect for agonists yield a straight line.

This is not the case with Suboxone.  With Suboxone the line would start out diagonal but then level off and become horizontal, as increasing doses would not increase the opiate effect.  Again, this is the basis for the use of Suboxone for opiate addiction treatment.  The horizontal portion of the curve would have an opiate effect equal to 30 mg of methadone, meaning that a person taking Suboxone would not be able to get a greater effect from Suboxone or other forms of buprenorphine. 

For most people, if Suboxone is taken correctly the flat part of the response occurs at about 2-4 mg of the drug.

The ceiling effect is also the reason for precipitated withdrawal;  if a person is taking an opiate agonist at a dose and effect greater than 30 mg of methadone, taking Suboxone will force the opiate effect lower, causing withdrawal symptoms.  The ceiling effect is also the reason that buprenorphine is a bit safer than a pure agonist;  the ceiling occurs at a level below that at which respiratory arrest is likely.  However, combining buprenorphine with other substances like alcohol or xanax will greatly increase the respiratory depression, and increase the risk of fatal respiratory depression– particulary if the substances are taken late at night and kick in when the person is sleeping, a time when respiratory drive is reduced a bit compared to during daytime.

Using your science knowlege…  what would the lines look like for agonists with different potencies such as morphine vs oxycodone?  (tic… tic…tic…) You would see lines that meet at the lower left corner and slope upward with different slopes, with the more potent agonists having steeper lines.  For antagonists like naloxone (effective intravenously) or naltrexone (effective orally) you would have flat lines that lie against the bottom of the chart.

My last point is that I take issue when I hear someone compare Suboxone to methadone, as they are totally different types of substances.  I find the comparison of Suboxone to naltrexone to be more appropriate, as the primary action of Suboxone with chronic use is opiate receptor blockade, not receptor activation.  I will point out to AODA counselors who despise Suboxone that they have no problem at all with giving a ‘sober’ recovering addict naltrexone;  the only difference with Suboxone is a small amount of opiate receptor activation that disappears with tolerance after a few days, essentially leaving behind a drug that looks identical to naltrexone.