II. Precautions: Risk of Abuse
- Gabapentin and Pregabalin (Lyrica) are abused by patients on Opiates to potentiate CNS Opiate effects
- More than one quarter of Opiate patients have abused Gabapentin
- Pregabalin (Lyrica) is more potent with faster onset and has higher abuse potential than Gabapentin
- Lyrica is categorized as DEA Controlled Substance Class V (and Gabapentin in several states)
- Smith (2012) Br J Gen Pract 62(601):406-7 +PMID:22867659 [PubMed]
III. Indications
- Neuropathic pain (Peripheral Nerve syndromes)
- Multiple Sclerosis
- Parkinson's Disease
- Fibromyalgia
-
Restless Legs Syndrome
- Effective in idiopathic RLS
- Effective in RLS among Hemodialysis patients
-
Epilepsy
- Generalized Tonic Clonic Seizures (rarely used)
- Partial Seizures (adjunctive agent, FDA approved)
- Bipolar Disorder
- Anxiety Disorder
-
Alcohol Dependence
- Doses of 600 mg orally three times daily appear to decrease Alcohol cravings
- Opioid Dependence
IV. Efficacy
- Chronic Pain (NNT 4.3)
- Diabetic Neuropathy (NNT 2.9)
- Postherpetic Neuralgia (NNT 3.9)
V. Safety
- Pregnancy Category C
- Excreted in Breast Milk
- Safe in liver disease (not hepatically metabolized)
VI. Mechanism
- GABA Amino Acid derivative (does not bind GABA-A or GABA-B Receptors)
- Binds presynaptic alpha2-delta1 subunit of Central Nervous System voltage-gated Calcium channels
- Decreases excitatory Neurotransmitter release and activity
VII. Metabolism
-
Bioavailability varies by dose
- Larger doses have lower Bioavailability
- Divided doses result in better Bioavailability
- Primarily renal excretion in its original form (not metabolized)
- Half-Life: 5 to 7 hours
- Therapeutic Dose: 4-8 ug/ml
VIII. Adverse Effects: Standard Dosing
IX. Adverse Effects: Overdose
- Acute Overdose: Sedative-Hypnotic effects
- Sleepy or lethargic
- Normal Vital Signs
- Chronic toxicity (especially with Renal Insufficiency)
- Progressive weakness
- Fatigue
- Altered Level of Consciousness
- Falls
X. Preparations: Newer related agents
-
Pregabalin (Lyrica)
- Indicated in Neuropathy
- More potent than Gabapentin, and possibly less Fatigue
XI. Dosing: Neuropathy in Adults
- Starting Dose
- Start at 300 mg orally at bedtime
- Advance to 300 mg orally three times daily (over 4-7 days)
- Plan to ultimately increase to 600 mg three times daily
- Patients tolerate starting 300 three times daily without titrating
- Fisher (2001) Neurology 56(6):743-8 [PubMed]
- Average Dose: 600 mg orally three times daily
- Maximum Dose: 1200 mg orally three times daily
- No increase in Bioavailability above 1200 mg orally three times daily
- Minimal pain benefit above 1800 mg/day in most conditions studied
- Stopping (similar to Pregabalin)
- Taper off agent over 1 week or more
- Avoid stopping abruptly due to withdrawal symptoms
XII. Dosing: Seizure Prophylaxis
- Age 3-12 years old
- Gabapentin 10-15 mg/kg (max 40 mg/kg) daily divided three times daily
- Age >12 years old
- Gabapentin 300-900 mg (max 1800) daily divided three times daily
XIII. Dosing: Miscellaneous
-
Postherpetic Neuralgia
- Day 1: 300 mg orally once
- Day 2: 300 mg orally twice daily
- Day 3: 300 mg orally three times daily
- Titrate as needed for reduction in pain (up to 1800 mg/day)
-
Restless Leg Syndrome
- Start 300 mg orally 2 hours before bed
-
Alcohol Dependence
- Target dose 600 mg orally three times daily (start lower and titrate to dose)
XIV. Drug Interactions
- No significant Drug Interactions
- However, Renal Insufficiency results in drug accumulation
XV. Disadvantages
- Low potency as antiepileptic
XVI. References
- (2016) Crit Dec Emerg Med 30(9):24
- LoVecchio (2022) Crit Dec Emerg Med 36(4): 36
- Lapoint (2021) EM:Rap 21(6): 16-7
- Wiffen (2005) Cochrane Database Syst Rev (3):CD005452 +PMID: 16034978 [PubMed]
Images: Related links to external sites (from Bing)
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