Comment · Fri, September 6, 2013 · Ceretropic
Is it necessary to maintain a piracetam blood serum level?
Original post in this thread
Damderiam · 20 points
With a half life of 4-5 hours it would require measuring and taking exact doses 3-4 times a day, and that's just not feasible all the time. However, there are plenty of medicines that continue to act, indirectly, after they've been eliminated. Am I getting any effect at all by taking it prior to bedtime, or would a morning dose be necessary as well? Since we don't know exactly how piracetam works I'll have to go by anecdotes and experimental evidence, but it's better than winging it. I figure it may, for example, increase the efficiency of sleep, or have lingering effects.
What they were answering
AgentLiquid · 3 points
Yeah this is the study that shows CSF levels being about 5% of blood levels: http://www.ncbi.nlm.nih.gov/pubmed/2384121
I couldn't find a similar study regarding piracetam. What are the general CSF concentrations with it?
In general though, it seems like the issue of BBB penetration is more complicated than just polarity of the molecule. See here: http://www.ncbi.nlm.nih.gov/pubmed/15207256
u/MisterYouAreSoDumb · Ceretropic
I read about 5 different piracetam pharmacodynamic studies in full last night, and none of them gave me ratios of CSF to plasma concentrations. Some said that piracetam "easily" crosses the blood brain barrier. However, none of them gave me numbers. So given that we know oxiracetam only reaches 5% plasma concentrations in the brain, piracetam "easily" crosses the BBB, and adding a hydroxyl group makes the molecule more polar, It's reasonable to assume piracetam reaches higher than 5% in CSF. However, I cannot unequivocally confirm that.
And yes, permeability of the BBB is more complicated than just lipid solubility. There is a bell curve to the relationship between permeability, lipid solubility, and the molar mass of the molecule. If a functional group adds lipid solubility to a molecule, that will only increase BBB permeability up to a certain mass. At that point it will reduce permeability, even though it's solubility goes up. But for sure adding a hydroxyl group will decrease lipid solubility and increase molar mass, so in oxiracetam's case it's pretty clear to me.