How long should the half life of ten milligrams of methadone in a 120 lb person be?

[Orchid_Suspiria]

I feel abit ignorant asking this question,but I've never been one for math and no one has been able to answer this for me.Any ideas?

[Forthesevenlakes]

Wikipedia gives the half-life as 24-36 hours, this sounds about right, given the drug's long duration of action. While looking for the half life, SWIM found one journal article stating that the duration of action for methadone is only 4-6 hours. This is a little odd, in SWIM's experience, methadone has always seemed to last much longer...up to a day in some cases.

[Dr.Jones]

Originally Posted by Forthesevenlakes

Wikipedia gives the half-life as 24-36 hours, this sounds about right, given the drug's long duration of action. While looking for the half life, SWIM found one journal article stating that the duration of action for methadone is only 4-6 hours. This is a little odd, in SWIM's experience, methadone has always seemed to last much longer...up to a day in some cases.

Some of the variability of enzyme activity in different people likely accounts for the large differences in clearance and half life of methadone seen within a population.15 For example, due to a polymorph of CYP 2D6, a subset of the white population, less than 10%, are considered to be poor metabolisers of methadone.18 Estimates of methadone half life vary from 15 to 55 hours.



That is what it says in the article and that is correct. Where did you get 4-6 hours. Auctually, I read a paper that was researching methadone doses and the idea of many (opiate naive/not on a program) die after taking the EXACT same dose as they did the day before or the day before that.

Day 1 =20mg dose
Day 2= 15mg dose
Day 3-12mg dose.

The blood plasma concentration should remain stable if that dose schedule is followed.

EG:

I take 20mg methadone today. I got super fucked up and it was great. The next day I take 20mg again. In reality, my methadone blood levels is high than it was the first day. And then the 3rd day I take 20mg again and die. The 3rd day, taking 20mg of methadone would give me the same blood concentration as taking ~28mg of methadone with none in your system, as even the 3rd day you have methadone in your system from the first day. I bet you want a source on this too huh. Well, Ill look here in a sec.

[Forthesevenlakes]

The source for the 4-6 hour statement is in the link above...note though that they state that those numbers are the duration of action, not the half-life.

[Dr.Jones]

Originally Posted by Forthesevenlakes

The source for the 4-6 hour statement is in the link above...note though that they state that those numbers are the duration of action, not the half-life.

Some of the variability of enzyme activity in different people likely accounts for the large differences in clearance and half life of methadone seen within a population.15 For example, due to a polymorph of CYP 2D6, a subset of the white population, less than 10%, are considered to be poor metabolisers of methadone.18 Estimates of methadone half life vary from 15 to 55 hours




That block of text was cut and pasted directly from the link your pasted. You must have misread. Even the sources cited are still linked. We are not talking about duration of action, but halflife. Even though its bassically the same thing, I didn't see anything about 4-6 hours duration of action

[Forthesevenlakes]

" Given the short duration of analgesia (4–6 hours) relative to methadone’s half life, the use of methadone as an analgesic agent requires a more frequent dosing regimen than the daily dosing used for the treatment of opioid dependence."

That's from the same article, in the 2nd paragraph of the "Methadone for Chronic Pain" section. I know the post was about half-life, I was just making an aside since that article came up when I was looking up the half-life. It just seemed odd that they'd say the duration of action is so short, to SWIM.

Good find on the halflife though, the 15-55 hour one seems like a more accurate representation of the widely varying half-life of this drug than wikipedia's 24-36 hours.