Posted by Larry Hoover on August 15, 2004, at 13:27:21
In reply to half lifes, posted by andromeda on August 14, 2004, at 11:28:53
> It seems like I take a med for awhile and then its just to much in my system after awhile. Is the half life med building up on itself?
For most medications, dosing schedules are set up so that you take a med again at roughly the length of the half-life. So, if a med has a half-life of eight hours, you take it three times a day. The idea is to maintain, as closely as possible, a steady blood concentration of the drug.
There is a "building" effect going on, but if you take a full dose at the point where the half of the original dose still remains (the definition of half life), and continue on in that pattern, the effect is to create a more or less stable blood concentration that stays between one and two times the peak concentration seen after the very first dose.
After a number of doses, you get a blood concentration which is represented by the infinite series: 1 + 1/2 + 1/4 + 1/8 + 1/16....
Again, using mathematical concepts, the sum of that series approaches the limiting value 2. At the half-life time, it falls to about 1, but then you take another dose, bringing it back to 2 again.
This assumes linear kinetics, but I'll stop there.
> I am very sensitive to meds in the first place.
Maybe you're simply being prescribed too much?
> Is it better to take a med about every 3 days instead of daily as not to get to much med in ones body?
No. Absolutely not. Your blood concentration would drop far too low before you took your next dose. You'd feel like a yo-yo.
> Am on abilify at this time for depression for bi-polar and am not exactly a happy camper to be honest.
Abilify has a very long half-life, about three days. Bear with me....what I just said is still true.
When a drug with a long half-life like Abilify is considered, the daily dosing is adjusted so that the buildup in the blood is the only consideration. The mathematical calculation of the total blood concentration is far more complicated under such conditions (I wouldn't even attempt it here), but the effect is known. You actually come out better off with daily dosing of a long half-life med, for two reasons. The decline in blood concentration is much smaller, proportionately, than that of shorter half-life meds, before the next dose. And, you don't have to try and remember which day your dose is to be taken. It's much easier to take a drug daily than every third day.
> Ended Lamictal and will probably be started on Topamax next. Been doing this for 12 years now and not getting much relief from any of the meds in the depressive phase. SSRI's actually cause mania in me.
I hope you will start using fish oil. It sounds like it might be just the ticket.
Lar
poster:Larry Hoover
thread:377551
URL: http://www.dr-bob.org/babble/20040811/msgs/377917.html