that using pregabalin alone and using it with an opioid pain reliever can depress breathing function. The other trial showed gabapentin alone increased pauses in breathing during sleep. The three observational studies at one academic medical center showed a relationship between gabapentinoids given before surgery and respiratory depression occurring after different kinds of surgeries. The FDA also reviewed several animal studies that showed pregabalin alone and pregabalin plus opioids can depress respiratory function. Overdose An overdose of Pregabalin usually consists of severe drowsiness, severe ataxia, blurred vision, slurred speech, severe uncontrollable jerking motions (myoclonus), tonic clonic seizures and anxiety. Despite these symptoms an overdose is not usually fatal unless mixed with another depressant. Several people with kidney failure developed myoclonus while receiving pregabalin, apparently as a result of gradual accumulation of the drug. Acute overdosage may be manifested by somnolence, tachycardia and hypertonia. Plasma, serum or blood concentrations of pregabalin may be measured to monitor therapy or to confirm a diagnosis of poisoning in hospitalized people. Pharmacology Interactions No interactions have been demonstrated in vivo. The manufacturer notes some potential pharmacological interactions with opioids, benzodiazepines, barbiturates, ethanol (alcohol), and other drugs that depress the central nervous system. ACE inhibitors may enhance the adverse/toxic effect of pregabalin. Pregabalin may enhance the fluid-retaining effect of certain anti-diabetic agents (thiazolidinediones). Pharmacodynamics Pregabalin is a gabapentinoid and acts by inhibiting certain calcium channels. Specifically it is a ligand of the auxiliary α2δ subunit site of certain voltage-dependent calcium channels (VDCCs), and thereby acts as an inhibitor of α2δ subunit-containing VDCCs. There are two drug-binding α2δ subunits, α2δ-1 and α2δ-2, and pregabalin shows similar affinity for (and hence lack of selectivity between) these two sites. Pregabalin is selective in its binding to the α2δ VDCC subunit. Despite the fact that pregabalin is a GABA analogue, it does not bind to the GABA receptors, does not convert into or another GABA receptor agonist in vivo, and does not directly modulate GABA transport or metabolism. However, pregabalin has been found to produce a dose-dependent increase in the brain expression of L-glutamic acid decarboxylase (GAD), the enzyme responsible for synthesizing GABA, and hence may have some indirect GABAergic effects by increasing GABA levels in the brain. There is currently no evidence that the effects of pregabalin are mediated by any mechanism other than inhibition of α2δ-containing VDCCs. In accordance, inhibition of α2δ-1-containing VDCCs by pregabalin appears to be