When looking up a pill with the imprint G6 (or G 6), identification depends heavily on the tablet’s physical characteristics (color and shape).
The most common prescription medications imprinted with “G6” or “G 6” are:
- Gabapentin 600 mg (Imprint: G 6 on a White, Oval tablet)
- Chlorpromazine Hydrochloride 50 mg (Imprint: G6 on a Gray, Round tablet)
- Fexofenadine Hydrochloride 180 mg (Imprint: G6 on a Peach/Pink, Oval/Capsule-shaped tablet)
Below is a detailed guide focusing primarily on Gabapentin 600 mg (the white oral tablet marked G 6), along with essential context for the other variants.
Physical Identification
Characteristic | Primary Matching Identification (Gabapentin) | Alternative Matching Identification (Chlorpromazine)
- Imprint G 6 (often with a space between G and 6) G6
- Color White Gray
- Shape Oval / Elliptical Round
- Active Ingredient Gabapentin (600 mg) Chlorpromazine HCl (50 mg)
- Drug Class Anticonvulsant / GABA Analog Phenothiazine Antipsychotic / Antiemetic
- Verification Warning: Always confirm both the imprint, shape, and exact color with a pharmacist before taking any unknown medication.
Mechanism of Action (Gabapentin 600 mg)
Although gabapentin is structurally related to the neurotransmitter gamma-aminobutyric acid (GABA), it does not directly bind to GABA-A or GABA-B receptors, nor does it affect GABA uptake or degradation.
- Target Receptor: Gabapentin binds with high affinity to the (alpha-2-delta) auxiliary subunit of voltage-gated calcium channels in central nervous system (CNS) tissues.
- Effect: Binding decreases calcium influx into presynaptic nerve terminals. This reduction modulates the release of excitatory neurotransmitters (such as glutamate, substance P, and norepinephrine), thereby dampening abnormal electrical activity in the brain (anticonvulsant effect) and interrupting pain signaling along damaged nerves (neuropathic pain relief).
Indications & Dosage
Gabapentin is FDA-approved for the management of postherpetic neuralgia (nerve pain following shingles) and as an adjunctive therapy for partial-onset seizures in adults and children.
Standard Adult Dosage Guidelines
- Postherpetic Neuralgia (PHN):
- Day 1: Single 300 mg dose.
- Day 2: 600 mg/day (given as 300 mg twice daily).
- Day 3: 900 mg/day (given as 300 mg three times daily).
- Maintenance: Doses are typically titrated up to 1,800 mg to 3,600 mg daily divided into three doses.
- Epilepsy (Partial Seizures):
- Starting Dose: 300 mg three times daily (900 mg/day).
- Maintenance: Effective daily range is usually 900 mg to 1,800 mg per day (divided into three doses). Doses up to 2,400 mg or 3,600 mg per day have been tolerated in clinical studies.
- Dosing Schedule Note: The maximum time between doses in a 3-times-daily regimen should not exceed 12 hours to avoid breakthrough seizure activity.
Precautions & Warnings
Key Warnings
- Suicidal Thoughts and Behaviors: Antiepileptic drugs (AEDs), including gabapentin, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication.
- Respiratory Depression Risks: The FDA warns that serious breathing difficulties may occur when gabapentin is used in patients with respiratory risk factors (such as COPD or asthma) or when co-prescribed with central nervous system depressants.
- Abrupt Withdrawal Hazard: Do not stop taking gabapentin abruptly. Sudden discontinuation may precipitate status epilepticus (continuous seizures) in patients taking it for epilepsy, or severe anxiety, sweating, insomnia, and pain in non-epileptic patients. Doses should be tapered gradually over at least 1 week.
- Misuse and Dependence Potential: While not a federally controlled substance in every jurisdiction, gabapentin is increasingly monitored due to potential for off-label abuse, especially among individuals with a history of substance use disorders.
Major Drug Interactions
Drug / Substance Interaction Risk Precaution
- Opioid Analgesics (e.g., oxycodone, morphine, fentanyl) Synergistic CNS and respiratory depression; severe sedation, profound dizziness, and overdose risk. Dose reductions of one or both drugs may be necessary; monitor breathing closely.
- Antacids (containing Aluminum or Magnesium) Antacids reduce gabapentin bioavailability and intestinal absorption by approximately 20%. Take gabapentin at least 2 hours after taking an antacid.
- Alcohol & CNS Depressants Additive sedation, drowsiness, impaired motor skills, and memory impairment. Avoid consuming alcohol while on gabapentin therapy.
- Hydrocodone Concomitant administration decreases hydrocodone exposure while increasing gabapentin levels. | Monitor for increased side effects of both medications.