Gabapentin can help relieve nerve pain in some people with postherpetic neuralgia (nerve pain after shingles) and peripheral diabetic neuropathy (nerve pain in the feet in people with diabetes). A Cochrane review reported that 3 to 4 patients out of every 10 with either of these conditions experienced at least a 50% reduction in pain intensity when prescribed gabapentin at dosages of 1800mg-3600 mg/day (gabapentin encarbil: 1200mg-3600 mg/day). This compared with only 1 or 2 out of every 10 given a placebo (an inactive treatment). People who had an improvement in pain relief with gabapentin are also expected to experience an improvement in sleep, fatigue, and in their mood.
This same Cochrane review reported that over half of those treated with gabapentin did not experience any worthwhile pain relief, but did experience side effects.
What type of nerve pain is gabapentin approved to treat?
Gabapentin is approved to treat nerve pain (neuralgia) that results from nerve damage. Gabapentin may be used to treat:
- Nerve pain caused by a herpes zoster viral infection, also known as shingles. This pain is called post-herpetic neuralgia (PHN), and it can be severe and chronic
- Nerve pain as a result of diabetic neuropathy, which happens when nerves in the feet damaged by diabetes cause chronic burning pain.
How does gabapentin work in nerve pain?
The exact way that gabapentin works to relieve pain is not known. It may change the way the body senses and reacts to pain. Gabapentin is used to manage long-term (chronic) pain, not to be taken for pain as needed. Chronic pain can interfere with sleep and work, and lead to depression.
How quickly does gabapentin work?
Studies show that pain relief may start within one week and reach a maximum effect in about 4 weeks. It can take this long because gabapentin is usually started at a low dose and gradually increased over time until it works.
For treating neuralgia, gabapentin is often started at 300 mg per day and gradually raised by 300 mg per day. One 2017 review of 37 studies found that pain relief usually occurs at a dose of 1,200 mg or more.
The same review compared gabapentin to an inactive medicine (placebo) in almost 6,000 adults with chronic pain from PHN or diabetic neuropathy. Study participants were given either gabapentin or a placebo for 4 to at least 12 weeks. The results showed that 30-40% of people taking gabapentin were able to reduce their pain by half or more, compared to 10-20% of people taking the placebo.
Although some people may get significant relief, others may have side effects without relief of pain. More than half of people taking gabapentin did not get significant relief and had side effects from the drug.
According to the review, about 60% of people taking gabapentin had side effects, including:
- Dizziness
- Sleepiness
- Water retention (edema)
- Clumsiness while walking (ataxia)
It does not typically make pain worse: In trials comparing gabapentin side effects to placebo side effects, only 1% of people reported increased pain, and this was the same for gabapentin and placebo.
Once you find the dose that relieves neuralgia for you, it is important not to stop taking it suddenly. Stopping suddenly can lead to withdrawal symptoms such as:
- Anxiety
- Insomnia
- Nausea
- Pain
- Sweating
Gabapentin is highly lipophilic but not bound to plasma proteins, showing linear pharmacokinetics and not demonstrating any significant protein binding or liver metabolization. It has an oral bioavailability of greater than 90%, independent of dose. Generally, patients achieve steady-state plasma levels within 24 to 48 hours. There is no clinically significant effect in administration with food nor on the extent of absorption or elimination. The elimination half-life of the drug is approximately 6.5 hours. Gabapentin readily crosses the blood-brain barrier. It is primarily excreted renally, with no active metabolites. Dosage adjustment is necessary for patients with renal impairment. Pregabalin does not induce or inhibit CYP enzymes. Also, none of the CYP enzyme inhibitors alter its pharmacokinetics as a consequence.
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Initial treatment with gabapentin is usually started with one dose of 300 mg per day and later increases the frequency to 3 times a day and dosage up to 4800 mg per day. The recommendation is to start the first dose in the evening and then take the drug three times a day.
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Usually, the effects are apparent in the first week of treatment but sometimes take about a month for significant improvement.
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Taper the dose over more than seven days to discontinue the medication.
For Partial Seizure
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300 to 1200 mg 3 times per day by mouth
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Max: 3600 mg per day
For Post-Herpetic Neuralgia
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300 to 600 mg 3 times per day by mouth
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Max: 1800 mg per day
For Neuropathic Pain
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300 to 1200 mg 3 times per day by mouth
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Max: 3600 mg per day
For Fibromyalgia
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400 to 800 mg 3 times per day by mouth
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Max: 2400 mg per day
Renal Dosing
Adjust the dose amount and frequency.
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Creatinine clearance of 30 to 60: 200 to 700 mg twice per day
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Creatinine clearance of 16 to 29: 200 to 700 mg once daily
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Creatinine clearance of 15: 100 to 300 mg once daily
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Creatinine clearance of less than 15: 125 to 350 mg as a supplement