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11-03-15 Why is Gabapentin ingestion increasing in nonmedical prescription opioid users?

Question of the Week

November 3, 2015

Why is Gabapentin ingestion increasing in nonmedical prescription opioid users?

A recent letter sent to poison centers around the country notified us that Gabapentin, typically an anticonvulsant, is being diverted. 

Gabapentinoids are used to treat seizure disorders as they decrease central neuronal excitability by binding at the calcium channel of hyperexcited neurons decreasing the release of excitatory molecules. They are also prescribed for neuropathic pain and generalized anxiety disorders.  They possess Gamma-aminobutyric acid (GABA)-mimetic properties through modulation of GABA metabolism and reversal of synaptic transporters.   Administration of Gabapentin to healthy volunteers increased GABA concentration by 56%.  (GABA is an inhibitory neurotransmitter whose receptors are stimulated by drugs like benzodiazepines) There is some evidence that Gabapentinoids have direct/indirect effects on the dopaminergic reward system.  At high concentrations, Gabapentinoids may possess both sedative and dissociative/psychedelic effects.

Surveys in substance misuse clinics report 22-38% of respondents admit to abusing gabapentin with other drugs to potentiate high or using Gabapentin by itself.  They report the following experiences with gabapentin abuse: euphoria, improved sociability, marijuana-like high/relaxation, zombie-like effects, and sedative-opiate buzz.

So what is happening in Tennessee?

One factor that may reflect the gabapentin abuse is the number of poison center calls we have received about Gabapentin.  These are exposure cases in which the patient intentionally took the medication, excluding suicide gestures.   Here are the numbers:

Year                            Calls

2011                            0

2012                            13

2013                            41

2014                            79

2015                            59 to date

Bottom Line:  Add this to your questions/knowledge about drugs of abuse/misuse.  Tennessee is one of the top states with opiate diversion.  I suspect there is a lot more gabapentin floating around than we realize.

This question prepared by:  Donna Seger, MD  Medical Toxicologist.  Data analysis by Justin Loden, PharmD  (Certified Specialist in Poison Information) Tennessee Poison Center.