Half Life and Maximum Concentration of Baclofen

[ignominious]

Every one is different and their reactions to drugs will be influenced by a great many factors.

When looking at the side effects of baclofen its useful to consider the half life of baclofen. Generally it is accepted that this is 2.5 - 6 hours in plasma/serum (blood). And that it takes about 1 hour for newly swallowed baclofen to get taken up.

There is an interesting graph program that can be downloaded here
Suboxone Withdrawal Taper Chart - Blood Plasma Level Taper Chart - Suboxone, Subutex & Reality
that will allow you to put in a daily dose and a half life and let you see when you get to maximum concentration in your blood.

Baclofen has a certain amount of trouble crossing the blood brain barrier and I think its likely that the half life in the brain would be longer.

If you look at the graph and put 6 hours as the half life then the concentration will pretty much maximise out after about 3-4 days. If you increase that half life to 12 hours which it maybe for the brain (central nervous system, cerebral spinal fluids) then the maximum concentration will occur after about 5 days.

At overdose levels the CNS may react in a different way to expelling the drug. There is some evidence that it will take up to 35 hours to eliminate 1/2 of the drug.
http://www.ncbi.nlm.nih.gov/pmc/arti...00240-0056.pdf

I think that its possible as we get near our switch that we increase the half life of baclofen in our CNS and therefore our SEs are affected less by the daily frequency of the dose.

[bleep]

Half Life and Maximum Concentration of Baclofen

Sober posted a link in my thread a while back that was interesting in this regard. With chronic dosing, the half life actually increases to about 6.5 hours. What a chronic dosing schedule is, I don't know, but I would imagine that most people here fit that bill.

[ignominious]

Half Life and Maximum Concentration of Baclofen

I think that's just about right. One article I read said that at 30mg a day, the bac in the cerebral spinal fluid was negligible but at higher doses it acts as a CNS deppressant.

As we go to higher doses we slow the CNS more and therefore the elimination half life gets longer. I think it may be one of the reasons why the SEs change and become stronger suddenly.

According to health dept. guidelines we are all taking high doses likely to affect our CNS. Which of course is the whole point of it.

[Evey]

Half Life and Maximum Concentration of Baclofen

Thanks for posting this, Ig. I guess I need to take this in to consideration more as I move along.

[ignominious]

Half Life and Maximum Concentration of Baclofen

I think it just helps to explain why some features change as we titrate up. I was a bit alarmed myself when I wasn't getting used to the dosage and my SEs wouldn't go away at the higher dose.

I think it worth pointing out that even, at a chronic overdose level of half life (35 hours), the build up to maximum concentration in your CNS will still take less than 2 weeks and a 10% reduction in dose will still drop the amount in your CNS substantially in 2-3 days.

I know the graph is intended for another med and is limited to one dose a day but it makes sense of why originally the protocol was 20mg every 3 -4 days and now Dr L is saying that in some cases to wait for a week or longer before increases.

[bleep]

Half Life and Maximum Concentration of Baclofen

Some good stuff here Ig - it explains perfectly why reducing the dose even a little seems to result in a massive decrease in SE's after a couple of days.

[ignominious]

Half Life and Maximum Concentration of Baclofen

It does illustrate that exactly. Have you been playing with the graph download?

[bleep]

Half Life and Maximum Concentration of Baclofen

I've done some fiddling. It's strange how you can end with a higher concentration than your actual dose would indicate. I would be interested to find out if it actually applies to baclofen, given that it's designed for a different drug, but I think that once you have changed the half-life to 6.5 hours, I can't see why it wouldn't.

[ignominious]

Half Life and Maximum Concentration of Baclofen

This was designed for a different drug but the way half life works is the same way for everything whether plutonium or baclofen. It's a logarithmic formula that I don't know and gets very confusing when you extrapolate over a few days!

With this download you can see the amount in your body if your titrating or tapering according to different half lives. The only limitation is that you have to lump your daily dose together for this download to work.

At the levels of baclofen that we are taking there is not so much information around about SEs and how long to expect them to last. This graph (which I assume can be done on EXEL) goes some way to explaining some things. Not much but better than nothing.

[bleep]

Half Life and Maximum Concentration of Baclofen

It will come in handy then for working out how much plutonium I can take. I would imagine it's relatively simple to do in Excel, once you know the formula. If I get bored at work this week I'll have a bash, but it's looking to be a pretty hectic week after such a nice long break!

[ignominious]

Half Life and Maximum Concentration of Baclofen

If you get the formula and can plug it into excel (spellin not too good!). I'd love to know how to do it but maybe I should join an evening class.

[ignominious]

Half Life and Maximum Concentration of Baclofen

DON'T EAT PLUTONIUM unless you're a fisherman off Tokyo. Barium has a half life of about 10 years but a biological half life of about 20 minutes because you will be rushing for the toilet.

For our purposes here its worth remembering that it takes a drug about 4 to 5 times as long as its half life to get up to a steady level in your body with regular doses. If the half life of baclofen in the CNS is say 25 hours then it will take 5 days before you get the full effect. Then a few more days until you get used to it and the SEs start reducing.

[beatle]

Half Life and Maximum Concentration of Baclofen

Thank you for this information and thread Ig. Very interesting. Still not sure what it means, but it's like a big puzzle, and we keep finding pieces, but we just don't know where they fit in. (Not a good analogy, I know.)

Also, I wonder if the actual half-life of any medication is different from individual to individual (in that their body processes, takes up, and eliminates chemicals at different rates and efficiencies)?

I know that I feel baclofen about 10 minutes after I take it on an empty stomach. It hits me with such a "bac" feeling that can't be confused with anything else. (Tingling fingers, buzzing brain.) In fact, this is sometimes how I determine whether I've skipped a dose or not.

With a meal, however, it is not very noticeable.

[ignominious]

Half Life and Maximum Concentration of Baclofen

Hi there beats

I'm sure that you're right, the half life varies for individuals, rates of metabolism. efficiency of kidneys etc.

Where I think this fits in is that the half life will vary for an individual as the dose increases which explains why for instance increasing the dose every 4 days may work well at the beginning but doesn't do the same thing later.

You clearly get a very quick uptake of bac into your system, for me I will feel it after 30 mins or so. There do seem to be 2 different effects going on which cause SEs. One is the concentration in the blood plasma (felt after a dose) and the other is the concentration in the brain which takes longer to seep in. Its the one in the brain that causes the main desired effect.

[bleep]

Half Life and Maximum Concentration of Baclofen

Hey Beatle, good to see you, it's been a while!

I was am still am confused by how long baclofen takes to hit me. Because I took it every two hours, for a long time I thought it was the current dose hitting me soon after I took it. Then I thought it was the previous dose. Now, I get no SE's at all, so will never know which dose it was that caused SE's. So for me, it was either 20 minutes, or two hours 20 minutes.

I think the distinction Ig makes here, between the blood plasma concentration and the CNS concentration is crucial. It's why people who don't experience bad SE's shouldn't just scream up through the doses, something I've been saying for a while, but not knowing the reason why.

I'm sure the half-life is different per individual, but not greatly so. You can probably take the given half-life as being accurate for each individual, give or take half an hour.

The ramifications for high dose baclofen actually require a bit of thought to be thrown at it, it goes a long way to explaining a lot of the mysteries of high dose baclofen SE's.