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Adverse Effects

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In 1993, Morris (i) described the efficacy and tolerability of gabapentin. He looked at

In 1993, Morris (i) described the efficacy and tolerability of gabapentin. He looked at 100 patients who were treated for epilepsy and found that at an average daily dose of just over 2000mg,

"Mild adverse events, commonly somnolence, fatigue, ataxia and dizziness, have been reported in about 75% of gabapentin recipients."

In 1994, Ramsay (ii) suggested that "Gabapentin is well tolerated.

Although adverse events occur in most patients receiving gabapentin as adjunctive therapy, they are transient and mild to moderate in severity."

Weight gain: DeToledo et al (iii) looked at the effect of gabapentin on weight and found that of 44 patients studied, weight gain occurred in 10 patients who gained more than 10% of their baseline weight, and 15 patients  who gained 5% to 10% of baseline.

Myoclonus: Asconape et al (iv) reported recently that gabapentin may be associated with myoclonus (muscle jerks). However, the authors have suggested that it is usually mild and it is not necessary to discontinue treatment with gabapentin in most cases.

Short-term memory problems may occur with gabapentin.

Lamotrigine may cause severe rash unless it is started at a very low dose and only very slowly titrated up.

However, it has been reported as well tolerated and safe.(v) Potentially severe and life-threatening CDRs (including Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis) are estimated to occur in 1 in 1000 adults and 1 in 50 to 100 children. (vi)

Fatalities have occurred during lamotrigine therapy, although the exact role of lamotrigine in these cases has not been definitely established.(vii) Lamotrigine has also been reported to cause anticonvulsant hypersensitivity syndrome.(viii)

Vitamin D: anticonvulsant drugs can inactivate vitamin D, and thus result in bone loss (ix). However, this does not appear to affect people exposed to plenty of sunshine (x). Vitamin D status can be measured by doctors.

i Morris GL 3rd Clin Ther 1995 Sep;17(5):891-900 Efficacy and tolerability of gabapentin in clinical practice.

ii Ramsay RE Neurology 1994 Jun;44(6 Suppl 5):S23-S30 Clinical efficacy and safety of gabapentin.

iii DeToledo JC, Toledo C, DeCerce J, Ramsay RE Ther Drug Monit 1997 Aug;19(4):394-396 Changes in body weight with chronic, high-dose gabapentin therapy.

iv Asconape J., Diedrich A., DellaBadia J., Epilepsia 2000 Apr;41(4):479-81 Myoclonus associated with the use of gabapentin

v Matsuo F, Gay P, Madsen J, Tolman KG, Rollins DE, Risner ME, Lai AA: Epilepsia 1996 Sep; 37 (9): 857-62 Lamotrigine high-dose tolerability and safety in patients with epilepsy: a double-blind, placebo-controlled, eleven-week study.

vi Anon. Drugs & Therapy Perspectives 1998; 11 (5): 11-13 Lamotrigine rash can be serious, especially in children.

vii Sterker M, Berrouschot J, Schneider D. Int J Clin Pharm Ther 1995; 33: 595-7 Fatal course of toxic epidermal necrolysis under treatment with lamotrigine.

viii Knowles SR, Shapiro LE, Shear NH. Drug Safety 1999; 21 (6): 489-501 Anticonvulsant hypersensitivity syndrome. Incidence, prevention and management.

ix Bone HG. JAMA 1983; 249:939 (review) Long-term anticonvulsant therapy and vitamin D metabolism 

x Williams C Netzloff M, Folkerts L, et al Am J Obstet Gynecol 1993;168:923-28 Vitamin D metabolism and anticonvulsant therapy: effect of sunshine on incidence of osteomalacia.