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Can somebody explain the math behind the reason larger doses of gabapentin are wasteful?

DeathRow

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So I’ve heard that doses beyond 300mgs of gabapentin are a waste, and that you should only take 300/hr to achieve better effects.

I did some research and found that 100mg of gabapentin has a bioavailability of 80%, 300mg is 60%, 400mg is 47%, 800mg is 34%, 1,200mg is 33%, and 1,600mg is 27%.

With simple math, 300mgs at 60% BA should mean 180mgs are absorbed, but 1,600mg at 27% BA should mean 432mgs are being absorbed, right? So wouldn’t it be more effective to take 1,600mg once an hour than 300mg once an hour?

Am I looking at this wrong? Am I retarded? I’m a little high and a little sleep deprived so totally might be.
 

WitchDr

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No the more you take the more effect you get. Maybe they meant there's no need to use over 300mg for new users? Idk but more mgs means more effect of course more addiction too.
 

PrincessDiz

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“Following oral administration, gabapentin is rapidly and reliably absorbed from the small intestine and. This occurs via a specific, though unidentified, transport mechanism that becomes saturated at higher doses.”

Basically, when you’re taking higher doses most of it is excreted in your urine, it’s not absorbed so it’s a waste of capsules. When the transport mechanism is saturated it can’t absorb any more of the drug. So why would you waste 1600mg for a mere 432mg? And that’s counting on the fact that you’re able to metabolise it properly.
 

DeathRow

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N
No the more you take the more effect you get. Maybe they meant there's no need to use over 300mg for new users? Idk but more mgs means more effect of course more addiction too.
No trust me, I did tons of research on this last night after I read about it here on BL and it is indeed true, the lat1 transporter gets over saturated at 300+mg so anything more than that is excreted. I can’t say I understand pharmacokinetics very well but after I sobered up it made sense to me. I was overthinking it.
 

DeathRow

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“Following oral administration, gabapentin is rapidly and reliably absorbed from the small intestine and. This occurs via a specific, though unidentified, transport mechanism that becomes saturated at higher doses.”

Basically, when you’re taking higher doses most of it is excreted in your urine, it’s not absorbed so it’s a waste of capsules. When the transport mechanism is saturated it can’t absorb any more of the drug. So why would you waste 1600mg for a mere 432mg? And that’s counting on the fact that you’re able to metabolise it properly.
Yeah I get it now I was indeed being retarded.
 

WitchDr

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Hmm well I take 1200 mg a day an if I take only 300 I start having withdrawals an 300mg isn't that strong but if I take 1200 mg at once I get fucked up
 

Skorpio

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Basically, when you’re taking higher doses most of it is excreted in your urine

Sorry for advance for the pedantry.

Non absorbed gabapentin is excreted in feces. For it to be filtered by the kidneys into the urine, it would have to make its way into the bloodstream, and the impediment to up take is the saturation of intestinal amino acid transporters.
 

PrincessDiz

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Sorry for advance for the pedantry.

Non absorbed gabapentin is excreted in feces. For it to be filtered by the kidneys into the urine, it would have to make its way into the bloodstream, and the impediment to up take is the saturation of intestinal amino acid transporters.
You’re incorrect, gabapentin is excreted solely through urine. Dose adjustments have to be made when it comes to people who have renal failure for example due to the fact that they can not clear it correctly and it can build up in the system becoming toxic.

here’s an interesting study for you to read.
 

Skorpio

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You’re incorrect, gabapentin is excreted solely through urine. Dose adjustments have to be made when it comes to people who have renal failure for example due to the fact that they can not clear it correctly and it can build up in the system becoming toxic.

here’s an interesting study for you to read.

I think we are both somewhat correct. Excretion happens after drug is absorbed into the blood. Hence the increase in dose with kidney failure.

That being said, gabapentin that is not being absorbed due to transporter saturation is passed in the feces.

What mechanism would there be to move drug not absorbed in the intestine into the urine?
 

PrincessDiz

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I think we are both somewhat correct. Excretion happens after drug is absorbed into the blood. Hence the increase in dose with kidney failure.

That being said, gabapentin that is not being absorbed due to transporter saturation is passed in the feces.

What mechanism would there be to move drug not absorbed in the intestine into the urine?
Did you read the study?
 

Skorpio

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Did you read the study?

Yes, excretion refers to the removal of a compound that has made it into the blood. The issue with gabapentin's limited absorbtion is that it does not enter the blood, as it needs to be actively transported from the intestines. The fraction of a dose that is not taken up by the amino acid transporters is not excreted because it has never been absorbed.

If you don't understand this, possibly read up on some principles of pharmacology re absorbtion distribution metabolism and excretion.
 

PrincessDiz

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Yes, excretion refers to the removal of a compound that has made it into the blood. The issue with gabapentin's limited absorbtion is that it does not enter the blood, as it needs to be actively transported from the intestines. The fraction of a dose that is not taken up by the amino acid transporters is not excreted because it has never been absorbed.

If you don't understand this, possibly read up on some principles of pharmacology re absorbtion distribution metabolism and excretion.
Gabapentin is absorbed from the proximal small bowel into the blood stream. The reason the bioavailability is limited with gabapentin is because it goes through the L amino acid transport system which is thought to be capacity limited. It does not induce hepatic enzymes and is excreted unmetabolised by the kidneys.
 

Skorpio

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Gabapentin is absorbed from the proximal small bowel into the blood stream. The reason the bioavailability is limited with gabapentin is because it goes through the L amino acid transport system which is thought to be capacity limited. It does not induce hepatic enzymes and is excreted unmetabolised by the kidneys.
You are getting close. Where are those transporters located?


I'm probably going to stop with this back and forth, neither of us are adding new info.. Here's a source for location and function of L amino acid transporters, search pubmed for other ones supporting it if you don't buy it,, there is a lot of published research.
 

Deru

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Gabapentin is absorbed from the proximal small bowel into the blood stream

If the transporters are saturated in the intestines, the rest would largely be eliminated as feces just like anything else that follows that path.
 
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PrincessDiz

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You are getting close. Where are those transporters located?


I'm probably going to stop with this back and forth, neither of us are adding new info.. Here's a source for location and function of L amino acid transporters, search pubmed for other ones supporting it if you don't buy it,, there is a lot of published research.
I’m enjoying the back and forth, if I’m learning something it’s worth it.

I’m gonna read a few more things today and get back to you. I will say, I have tested my own urine and faeces and found minimal amounts of gabapentin in the latter and I was on the max amount per day. Although, I do have a rare condition and gastroparesis which is maybe why I was so badly effected by gabapentin.
 

Skorpio

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I have tested my own urine and faeces and found minimal amounts of gabapentin in the latter and I was on the max amount per day.

That's extremely interesting and relevant. What method did you use?
I'm down to reply as long as new stuff keeps occurring.

Slowed gi movement should increase absorbtion, as it would allow for the drugs to have more time near the transporters. I wonder how significant of an effect this is with the gut slowdown of mu opioid use, as that could really change up the commonly viewed paradigm with gabapentin.
 

PrincessDiz

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That's extremely interesting and relevant. What method did you use?
I'm down to reply as long as new stuff keeps occurring.

Slowed gi movement should increase absorbtion, as it would allow for the drugs to have more time near the transporters. I wonder how significant of an effect this is with the gut slowdown of mu opioid use, as that could really change up the commonly viewed paradigm with gabapentin.
Well I had use of a GC/MS to test. I actually work in a lab and test drugs and drug batches (medications basically). I work with rodents too and double check studies carried out by drug companies, a fail safe i think someone called it recently.

I actually am on tapentadol also due to my condition but again i have a rare condition and weird genes. I metabolise most medication super quick. I’ve woken up during every surgical procedure I’ve had for example. Although not gabapentin or pregabalin which was weird. They seem to go through my system at a much slower than usual pace. I’m basically going to do my PHD in pharmacogenetics which is another 4 years but whatever. It interests me quite a bit. Obviously I have a lot to learn.

As for the gut slowdown for a normal opiate/opioid user I have seen studies suggest a much higher bioavailability when it comes to gabapentin.
 

LordOfThisWorld

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I just took 6 mg of Etizolam, 50mg of seroquel, and do to serious shoulder socket pain where it’s unbearable I took 800mg Ibuprofen prescription strength, well after 4 hours, the pain can back, so after 5 hours I took 1000mg of Tylenol , so about 5 hours the pain came so I took naproxen 500mg, my question is can I take 300 mg of gabapentin after taking all these pain meds and 6mg Of Etizolam?

I don’t want to die but the pain is unbearable and keeps coming back, and I figure maybe the gabapentin would take the pain away, but I don’t want all these mixtures I took to make me sick or overdose.

can someone help this is harm reduction I’m asking for.
 
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