gabapentin

sources:

• https://en.wikipedia.org/wiki/Gabapentin
• https://en.wikipedia.org/wiki/Gabapentinoid
• https://en.wikipedia.org/wiki/Pregabalin
• https://slatestarcodex.com/2019/07/18/know-your-gabapentinoids/

Confusingly, although gabapentin is a structural analogue of GABA (adding a cyclohexane ring to the GABA backbone): it doesn't bind to GABA receptors, doesn't convert into GABA, and doesn't appear to modulate GABA transport or metabolism. Instead it seems that the primary mechanism of action is binding to and inhibiting the α2δ subunit of voltage dependent calcium ion channels (note that phenibut also does this, in addition to its GABAergic action), preventing the release of excitatory neurotransmitters like glutamate, dopamine, norepinephrine, etc.

When taken orally it is absorbed via the "large neutral amino acid transporter" LAT1, which is easily saturated, so there are diminishing returns to larger doses: a 100mg dose is 80% bioavailable while a 300mg dose only 60%. The time to peak levels ($T_{max}$) is about 1.7 hours, and elimination half-life is 5-7 hours.