Gabapentin

How it works

     * Gabapentin is a medicine that may be used for the treatment of
       certain seizure disorders or nerve pain.
     * Experts aren't sure exactly how gabapentin works, but research has
       shown that gabapentin binds strongly to a specific site (called the
       alpha2-delta site) on voltage-gated calcium channels. This action
       is thought to be the mechanism for its nerve-pain relieving and
       anti-seizure properties.
     * Gabapentin enacarbil (brand name Horizant) is a prodrug of
       gabapentin which has been designed to overcome the limitations of
       gabapentin, such as poor absorption and a short duration of action.
       Gabapentin enacarbil is effective for restless legs syndrome (RLS)
       and postherpetic neuralgia (nerve pain that occurs following
       Shingles).
     * Gabapentin belongs to the group of medicines known as
       anticonvulsants.

Upsides

     * May be used in addition to other medication to reduce seizure
       frequency in adults and children aged three and older with partial
       onset seizures.
     * May be used in the management of postherpetic neuralgia (persistent
       nerve pain following Shingles infection) in adults.
     * Gabapentin enacarbil (brand name Horizant) may be used to relieve
       restless legs syndrome (RLS) or nerve pain associated with
       postherpetic neuralgia. This prodrug of gabapentin only requires
       once-daily dosing.
     * Gabapentin is available as a generic; however, not all generics are
       interchangeable with some branded versions of gabapentin.
     * Gabapentin may be used off-label (this means for an indication that
       has not been approved by the FDA but may still have a place in
       therapy) for some other indications such as fibromyalgia,
       persistent hiccups, migraine prevention and hot flashes.

Downsides

   If you are between the ages of 18 and 60, take no other medication or
   have no other medical conditions, side effects you are more likely to
   experience include:
     * Dizziness, drowsiness, tiredness, fever, and nystagmus (a rapid and
       uncontrollable movement of the eyes). Drowsiness caused by
       gabapentin may affect your ability to drive or operate machinery.
       Alcohol and other drugs with sedative properties enhance this
       effect.
     * May cause behavioral problems, hostility or aggression, or thought
       disturbances when used to treat epilepsy in children aged three to
       twelve years.
     * Other side effects may include blurred vision, amblyopia (lazy
       eye), dry mouth, peripheral edema (fluid retention in the feet and
       hands), tremor, sexual dysfunction and gastrointestinal
       disturbances.
     * Best titrated up slowly to reduce the risk of side effects;
       however, this may delay the onset of an effect.
     * Similar to other anticonvulsant medicines, gabapentin may increase
       the risk of depression and suicidal thoughts, particularly in young
       adults under the age of 24.
     * Gabapentin has been associated with a discontinuation syndrome when
       abruptly stopped. Symptoms include anxiety, insomnia, nausea, pain,
       and sweating. It should be tapered off slowly under a doctor's
       advice.
     * The dosage of gabapentin needs to be reduced in kidney disease.
     * Rarely, hypersensitivity reactions may occur. Symptoms may include
       fever, rash, swollen lymph nodes, swollen facial features or
       throat.
     * May interact with some other medications including antacids,
       hydrocodone, morphine, and other drugs that cause sedation or
       dizziness. May also cause false positive results on some urinary
       protein tests.
     * There have been some reports of gabapentin misuse and abuse,
       particularly in people with a history of drug abuse. Be alert for
       this possibility.
     * Gabapentin requires three times daily administration because of its
       short duration of effect. Gabapentin enacarbil (brand name
       Horizant) only requires once-daily dosing.
     * Only effective for partial onset seizures, not other types of
       seizure disorders.
     * Some branded and generic forms of gabapentin are not
       interchangeable.

   Notes: In general, seniors or children, people with certain medical
   conditions (such as liver or kidney problems, heart disease, diabetes,
   seizures) or people who take other medications are more at risk of
   developing a wider range of side effects. For a complete list of all
   side effects, [84]click here.

Bottom Line

   Gabapentin may be used in the treatment of partial onset seizures and
   nerve pain but is likely to cause dizziness or drowsiness. Gabapentin
   enacarbil (brand name Horizant), a prodrug of gabapentin that can be
   taken once daily, may be used in the treatment of RLS and postherpetic
   neuralgia.

Tips

     * The Neurontin brand of gabapentin can be taken with or without
       food. If you break a 600mg or 800mg Neurontin tablet in half, be
       sure to take the other half at your next dose or within 28 days.
     * The Gralise brand of gabapentin cannot be substituted for other
       gabapentin products due to differing administration requirements
       (once daily versus three times daily for other products). Gralise
       should be taken with food at the evening meal. Gralise tablets
       should be swallowed whole; do not cut, crush, or chew.
     * Horizant (gabapentin enacarbil) tablets should be swallowed whole
       and taken with food. For restless leg syndrome, take at roughly 5
       PM in the evening. Do not cut, crush, or chew the tablet. Do not
       interchange Horizant with other gabapentin products.
     * Use a manufacturer-provided or pharmacist-provided measuring cup
       calibrated for liquid formulations when measuring liquid doses of
       gabapentin. Do not use a kitchen measuring device or teaspoon
       because these may be inaccurate.
     * For dosage schedules of three times daily do not allow more than 12
       hours between doses.
     * Monitor for mood changes and report any evidence of new or
       worsening mood or depression to the prescribing doctor.
     * Do not take gabapentin at the same time as antacids such as Maalox
       or Gaviscon. Separate administration by at least two hours. Take
       exactly as directed by your doctor, do not increase or decrease the
       dose without his or her advice.
     * Avoid operating machinery, driving, or performing tasks that
       require mental alertness if gabapentin makes your drowsy or impairs
       your judgment.
     * The side effects of gabapentin, such as dizziness or drowsiness,
       may increase your risk of falling. Remove any fall hazards from
       your home if possible (such as loose rugs), and be careful when
       ascending or descending stairs.
     * Talk to your doctor if you experience any worsening of your mood or
       if you develop any suicidal thoughts.
     * Do not stop taking gabapentin without your doctor's advice as it
       may precipitate a withdrawal reaction (symptoms include agitation,
       disorientation, confusion). When the time comes to discontinue
       gabapentin your doctor will tell you how to taper it off.
     * Seek urgent medical advice if you develop a rash, fever, difficulty
       breathing or facial swelling while taking gabapentin.

Response and Effectiveness

     * Peak concentrations of gabapentin (immediate-release) occur within
       2 to 3 hours. Although gabapentin may improve sleep problems due to
       nerve pain within a week, it may take up to two weeks for symptom
       relief from nerve pain to occur. A reduction in seizure frequency
       is usually apparent within a few weeks.
     * Gabapentin enacarbil (brand name Horizant), a prodrug of
       gabapentin, is rapidly absorbed by nutrient transporters along the
       gastrointestinal tract and then quickly hydrolyzed to gabapentin.
       This means gabapentin enacarbil only needs to be given once a day.
       However, symptom relief from RLS or postherpetic neuralgia may take
       several days or weeks to develop.
     * Immediate-release gabapentin capsules require three times daily
       dosing (except in kidney disease).

References