Metadoxine for ADHD

Metadoxin (pyridoxine pyrrolidone carboxylate; pyridoxol L-2-pyrrolidone-5-carboxylate).
Metadoxine is an ion-pair salt of pyridoxine (vitamin B6) and 2-pyrrolidone-5-carboxylate (PCA, L-PGA).¹

Metadoxine retarded is referred to as METADOXINE EXTENDED RELEASE (MDX) in the USA.

Metadoxine is currently being researched for the treatment of ADHD.²

is a selective serotonin 2B receptor antagonist³
- It is assumed that a disturbed balance of serotonin-dopamine neurotransmission is involved in ADHD symptoms in adults.⁴
shows high affinity to the GABA transporter
- Metadoxin inhibits the activity of the enzyme GABA transaminase, which breaks down GABA.
- Metadoxin increases inhibitory GABA-ergic synaptic transmission through a presynaptic effect.
- As it does not affect dopamine, noradrenaline or serotonin levels, metadoxine has a novel mechanism of action as a monoamine-independent GABA modulator[8].
inhibits the excitatory transmission of glutamate
- this may improve attention in people with ADHD⁵

Metadoxin does not bind:¹

Dopamine receptors or dopamine transporters
Noradrenaline receptors or noradrenaline transporters
Serotonin receptors
Does not change the level of dopamine, noradrenaline or serotonin

Several double-blind, placebo-controlled studies in adults with ADHD with metadoxine sustained-release (1400 mg/day) found a significant clinical improvement compared to placebo (only) in patients with predominantly inattentive symptoms (ADHD-I).⁶⁵⁷

The drug did not pass a Phase III trial. No significant improvement was found compared to placebo, although this could also have been due to above-average improvements with placebo.⁸ According to another source, the Phase III trial was terminated prematurely by the FDA due to safety concerns.⁹

Metadoxine could also be helpful in acute alcohol intoxication and in fragile X syndrome (FXS), which has symptoms that can be confused with ADHD.¹⁰

Metadoxin improved in an FXS animal model (Fmr1 knockout mouse)

Learning behavior
Memory
social interaction

Metadoxin also reversed the overactivation of the biomarkers Akt and extracellular signal-regulated kinase (ERK) in the blood and brain of juvenile and adult mice. Metadoxin restored the aberrant neuronal morphology in FXS and reduced the excessive basal protein production that is thought to be responsible for learning and memory deficits in FXS.¹¹¹²

Side effects of Metadoxin

Metadoxin did not show any severe side effects.
The most common side effects were

Nausea
Tiredness
Headache.