[pacman_789]

Does anyone know the half life of lithium (the immediate release, not the extended release)? I know the ER version is a 24 hour pill, but not sure about the IR one. My pdoc started me on lithium carbonate 150mg IR since the 300 mg ER was too strong for me (i'm very sensitive to medications and usually have to take them at the lowest dose available). She said I could start out at once a day even though most people take it twice a day. So, just wondering if anyone has insight as to how long it actually is supposed to last. I find myself always wondering about it after about 12 hours have passed, and I start analyzing my behavior to see if it has worn off lol (prob my OCD kicking in).

Thanks,

Andrew

The following paragraphs are included at Lithium Carbonate - FDA prescribing information, side effects and uses, which is generally a reliable site.

Pharmacokinetics

After oral administration, lithium is reported to be completely absorbed in the upper gastrointestinal tract. Peak serum concentrations (Tmax) occur 0.25 to 3 hours after oral administration of immediate release preparations and 2 to 6 hours after sustained-release preparations.

The distribution space of lithium approximates that of total body water, and the plasma protein binding is negligible. After equilibrium, the apparent volume of distribution is 0.7 to 1 L/kg. Lithium is not metabolized.

Lithium is primarily excreted in urine, proportionally to its serum concentration. Lithium is filtered by the glomerulus, and 80% is reabsorbed by passive diffusion in the proximal tubule. The elimination half-life of lithium is approximately 18 to 36 hours. Lithium excretion in feces is insignificant.

I only ever took Lithium ER, not the instant release. I was always prescribed to take it twice per day, despite it being an extended release form, though I took much higher daily doses than you. In general, I usually need fairly high doses of medications, with just a couple of exceptions.

I hope your new arrangement works out better for you.

[Pookyl]

I’ve taken both types of Lithium and always twice a day. I’ve been on Lithium for almost 4 years.
I’m on a high dose of 1350mg/day but my Lithium blood levels are stable and healthy at 0.8

[pacman_789]

Originally Posted by BirdDancer

The following paragraphs are included at Lithium Carbonate - FDA prescribing information, side effects and uses, which is generally a reliable site.

Pharmacokinetics

After oral administration, lithium is reported to be completely absorbed in the upper gastrointestinal tract. Peak serum concentrations (Tmax) occur 0.25 to 3 hours after oral administration of immediate release preparations and 2 to 6 hours after sustained-release preparations.

The distribution space of lithium approximates that of total body water, and the plasma protein binding is negligible. After equilibrium, the apparent volume of distribution is 0.7 to 1 L/kg. Lithium is not metabolized.

Lithium is primarily excreted in urine, proportionally to its serum concentration. Lithium is filtered by the glomerulus, and 80% is reabsorbed by passive diffusion in the proximal tubule. The elimination half-life of lithium is approximately 18 to 36 hours. Lithium excretion in feces is insignificant.

I only ever took Lithium ER, not the instant release. I was always prescribed to take it twice per day, despite it being an extended release form, though I took much higher daily doses than you. In general, I usually need fairly high doses of medications, with just a couple of exceptions.

I hope your new arrangement works out better for you.

Thanks, Bird Dancer. For some reason, I had trouble finding articles written about the IR since most people seem to take the ER. 18 to 36 hours is a wide range, so I guess I just need to do a trial period and try not to overthink it too much.