Side effects of phenibut include sedation, sleepiness, nausea, irritability, agitation, dizziness, and headache, among others. Overdose of phenibut can produce marked central nervous system depression including unconsciousness. The medication is structurally related to the neurotransmitter γ-aminobutyric acid (GABA), and hence is a GABA analogue. Phenibut is thought to act as a GABAB receptor agonist, similarly to baclofen and γ-hydroxybutyrate (GHB). However, at low concentrations, phenibut mildly increases the concentration of dopamine in the brain, providing stimulatory effects in addition to the anxiolysis. Subsequent research has found that it is also a potent blocker of α2δ subunit-containing voltage-dependent calcium channels (VDCCs), similarly to gabapentinoids like gabapentin and pregabalin.