Thursday, 26 May 2011

Gabapentin (Neurontin)

(...Treatments 4)
It's another long-winded post I'm afraid. You may well be prescribed Gabapentin or Neurontin so it'll help you get an idea of how or whether it works.
Gabapentin (Neurontin)belongs to the group of drugs normally used to treat epilepsy and seems to be a treatment with more plusses than negatives mainly because it very importantly doesn't clash with existing HIV drugs. It works by stabilising electrical activity in the brain and has thus been found to help with neuropathic nerve disruption or disfunction.
You need to look out for skin problems, dizziness or sleepiness, especially if you're driving any sort of vehicle (even a bicycle) and you also have to be alert to sudden depression or even suicidal feelings. You should try to be consistent with the times you take the drug and shouldn't suddenly stop taking it without advice, or you may run the risk of a seizure. It's something that needs to taken under advice and be controlled but remember, as always, the first control post is yourself - if anything doesn't feel right, ask the doctor.




Title: Fast Fact and Concept #49: Gabapentin for Neuropathic Pain

Author(s): Anita Kishore; Linda King

Gabapentin (Neurontin) is now widely used for neuropathic pain. Controlled clinical trials in diabetic neuropathy and postherpetic neuralgia show that gabapentin at 2400-3600 mg/day has an efficacy similar to the tricyclic antidepressants. Consistent, though less compelling clinical evidence supports its use for a variety of other neuropathic pain syndromes, including cancer pain syndromes, pain associated with HIV infection, chronic back pain and others. The exact mechanism and site of action of gabapentin is unknown. Its use for neuropathic pain has become widespread because it is generally well-tolerated, easily titrated, has few drug interactions, and does not require laboratory monitoring. However, cost may be a limiting factor for some patients.

Patients suitable for Neurontin should ideally have a clear neuropathic pain syndrome, characterized by sharp, shooting, lancinating and/or burning pain, in a nerve root (radicular) or stocking/glove distribution.

Adult Dosing
Gabapentin is started at low doses (100 mg qD to 100 mg TID) and increased by 100 - 300 mg every 1-3 days to effect (a typical schedule might include: Day 1: 300 qhs; Day 3: 300 mg BID; Day 5: 600 mg BID, Day 7: 600 mg TID). The usual effective total daily dose is 900-3600 mg, administered in three divided doses per day; higher doses may be needed. Titration should proceed more slowly in elderly patients.

Dosing in Renal Failure
Gabapentin doses must be reduced for patients with renal insufficiency.

Adverse Reactions
Sedation and confusion, as well as dizziness and ataxia, are the most common side effects, especially with rapid dose titration. Tolerance to these effects appears to develop within a few days if the dose is held at the highest tolerated dose until symptoms improve or stabilize.

Dosage Formulations
Neurontin is available in 100 mg, 300 mg, and 400 mg capsules, 600 mg and 800 mg tablets, and as a liquid (250mg/5mL).

Cost
Neurontin is more expensive ($100-$200 per month) than other agents used for neuropathic pain (tricyclic antidepressants and older anti-epileptic drugs such as carbamazepine). An indigent drug program is available from the manufacturer.

Summary

Gabapentin is a safe and effective adjuvant analgesic for neuropathic pain. Physicians should become comfortable using and titrating gabapentin in patients with neuropathic pain syndromes.


References
American Pain Society. Principles of Analgesic Use in the Treatment of Acute Pain and Cancer Pain. 1999.

...and the results of placebo trials are also generally positive:

A placebo-controlled trial of gabapentin for painful HIV-associated sensory neuropathies.

Hahn K, Arendt G, Braun JS, von Giesen HJ, Husstedt IW, Maschke M, Straube ME, Schielke E; German Neuro-AIDS Working Group.

Source
Department of Neurology, Charité Campus Mitte, Schumannstr. 20/21, D-10117 Berlin, Germany. katrin.wetzel@charite.de


BACKGROUND:

Painful HIV-associated sensory neuropathies (HIV-SN) are a common complication of HIV infection. The pathogenesis is unknown and the treatment very limited. Gabapentin (GBP) is effective in painful diabetic neuropathy and postherpetic neuralgia and its effectiveness on painful HIV-SN has been reported anecdotally.

DESIGN:

Multicenter, prospective, randomised, double-blind, placebo-controlled study.

METHODS:

Patients were followed for a 1-week screening, a 4-week double-blind and a 2-week open treatment phase. GBP was initiated at 400 mg/d, titrated over 2 weeks to 1200 mg/d, and then either maintained at this level or-if not beneficial-titrated to 2400 mg/d. After 4 weeks the medication was unblinded and the patient had the choice to begin, to maintain or to increase GBP to 3600 mg/d. The primary outcome measure was an improvement in median pain on the Visual Analogue Scale (VAS) from the screening week compared to the 4(th) treatment week. A secondary efficacy measure was the median sleep score (VAS).

RESULTS:

15 patients received GBP and 11 placebo. In each group one patient dropped out during the doubleblind phase. Median pain (GBP 5.1; placebo 4.7) and sleep score (GBP 4.5; placebo 5.6) did not differ between both groups at baseline. In the GBP-group there was a significant decrease of the pain to 2.85 (-44.1 %) as well as of the sleep VAS to 2.3 (-48.9 %). No significant decrease in the pain (median VAS=3.3, -29.8 %) as well as in the sleep score (median VAS=4.95, -11.6 %) was observed in the placebo-group. GBP was generally well tolerated. The most frequent side effect was somnolence reported in 80% of GBP-treated patients.

CONCLUSIONS:

GBP was more effective than placebo in reducing pain and sleep interference in patients with HIV-SN.

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