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Location: Denver
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perhaps this will prove helpful on the Neurontin. not sure about the SSDI.
GABAPENTIN: NEUROPATHIC PAIN AND WEIGHT GAIN
Wise Young, Ph.D., M.D.
W. M. Keck Center for Collaborative Neuroscience
Rutgers University, New Brunswick, NJ 08854
10 March 2006
Gabapentin (Commerical name: Neurontin) was first developed to treat epilepsy and recently discovered to have some beneficial effects for neuropathic pain. The drug is remarkably non-toxic. Studies of developmental toxicity in pregnant animals at doses of 500-3000 mg/kg (mice) and 60-1500 mg/kg (rats and rabbits) revealed no adverse maternal or fetal effects in mice or rats but at 1500 mg/kg, one rabbit died, four aborted, and the rest had reduced food consumption and body weight gain, while the rabbit fetuses showed no significant effect of the drug (Petrere and Anderson, 1994).
Early clinical studies suggested that gabapentin can cause weight gain in a small percentage of patients. In 1995, Morris (Morris, 1995) studied 100 patients (47 men and 53 women) who took a variety of anticonvulsant drugs, including gabapentin. Gabapentin reduced seizures by more than 50% in 72 patients and 23 patients had 75% reduction of seizures; 57% continued gabapentin treatment and 5 remained seizure-free on gabapentin monotherapy without complication. The mean daily dose was 2107 mg. Transient fatigue was the most common side-effect, affecting 20 patients. Seven patients had ataxia but 6 of these were taking another anti-seizure drug (carbamazepine). Two of the patients experienced wight gain.
Long-term exposure to high-dose gabapentin may suppress weight gain in rats. In 1995, Sigler, et al. (Sigler, et al., 1995) did a 2-year tumor bioassay in male Wistar rats, fed 250, 1000, and 2000 mg/kg doses for 104 weeks. While treatment resulted in 8-16% incidence of pancreatic acinar neoplasia, there were no increase in other tumor types and there was no tumor increase in female rats. The tumors were not invasive, did not metastasize, and did not increase mortality. Rats receiving 1000 and 2000 mg/kg showed body weight suppression.
Long-term gabapentin causes weight gain in epileptic patients. In 1997, DeToledo, et al. (DeToledo, et al., 1997) reported that epileptic patients who received gabapentin doses greater than 3000 mg/day for 12 months or longer had weight gain. In 44 patients, 10 (23%) had greater than 10% body weight gain, 15 (34%) had 5-10% body weight gain, 16 (36%) had no change, and 3 (7%) lost 5-10% body weight. Body weight gain occurred in patients taking gabapentin with other drugs but also in those taking gabapentin alone. In 1998, Baulac, et al. (Baulac, et al., 1998) studied 610 patients receiving 900-2400 mg/day of gabapentin for 6 months and only 8.8% of the patients showed weight gain. Postmarketing surveillance of 3100 patients in England suggest similar results (Wilton and Shakir, 2002).
The weight gain produced by gabapentin is similar to that produced by other drugs such as propranolol, atenelol, verapamil, and valproate, affecting only a modest number of patients (Maggioni, et al., 2005). A greater weight gain at 6 months was found in patients taking pizotifen, amitriptyline, and propranolol. Other psychotropic drugs can cause weight gain, such as clozapine, alanzepine, and some antidepressants such as amitryptyline, mirtazapine, lithium, valproic acid, carbamazepine, topiramate, zonisamide, and and some serotonin inhibitors (Ness-Abramof and Apovian, 2005), as well as pregabalin (Hamandi and Sander, 2006) and other new antiepileptic drugs (Marken and Pies, 2006).
If a person with neuropathic pain has weight gain from gabapentin, what alternatives are there? Gabapentin is structurally related to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and readily crosses the blood brain barrier (Morris, 1999), affecting presynaptic calcium channels to influence neurotransmitter release (Cheng and Chiou, 2006). As an anti-epileptic drug, gabapentin is not particularly effective as a monotherapy but may be useful in combination with other drugs (Harden, et al., 2005). Gabapentin relieves neuropathic pain in some patients, but a recent literature review suggest that amitriptylline and carbemapazine may be more beneficial and cheaper (Cepeda and Farrar, 2006).
Pregabalin, a structural congener of gabapentin, is a new anti-convulsant that was provisionally approved by the US Food and Drug Administration in December 2004 for treating neuropathic pain (Guay, 2005). In doses of 50-200 mg three times a day, pregabalin was superior to placebo for treatment of diabetic peripheral neuropathy and postherpetic neuralgia (p<0.001 to p<0.049) in several clinical trials. Weight gain was seen in about 14% of the patients at the highest dose of 600 mg/day (Hamandi and Sander, 2006).
In summary, gabapentin seems to cause weight gain in a modest proportion of patients. The weight gain appears to be more common with higher doses exceeding 3000 mg/day and longer term therapies of 6 months or longer. Many other drugs that may be useful for neuropathic pain also seem to induce weight gain in 8-10% of patients. It may, however, be worthwhile to try these other drugs.
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