Clinical predictors of response to lamotrigine and gabapentin monotherapy in refractory affective disorders.
BACKGROUND
The objective of the current study was to examine possible clinical predictors of positive response to lamotrigine or gabapentin monotherapy in treatment-refractory affectively ill patients.


METHODS
Forty-five patients with treatment refractory bipolar (n = 35) or unipolar (n = 10) affective disorder participated in a clinical study evaluating six weeks of treatment with lamotrigine, gabapentin, or placebo monotherapy given in a double-blind, randomized fashion with two subsequent cross-overs to the other agents. Patients received daily mood ratings and weekly cross-sectional scales. Much or very much improved on the Clinical Global Impression scale modified for bipolar illness was considered a positive response. Degree of response was correlated with a number of baseline demographic and course of illness variables in a univariate analysis and then by linear regression.


RESULTS
Response rates to lamotrigine (51%) exceeded those to gabapentin (28%) and placebo (21%). A positive response to lamotrigine monotherapy was associated with a bipolar diagnosis; fewer hospitalizations; fewer prior medication trials; and male gender (of which the latter two variables survived logistic regression). For gabapentin, degree of response correlated with shorter duration of illness; younger age; and lower baseline weight (with the latter two surviving linear regression).


CONCLUSIONS
In this highly treatment-refractory population, lamotrigine appeared most effective for male patients with fewer prior medication trials. Gabapentin monotherapy, although not better than placebo, appeared most effective in those with younger age and lower baseline weight. These preliminary data in a treatment refractory subgroup may help in the further definition of the range of clinical utility of these widely used anticonvulsants.
Obrocea
Gabriela V
GV
National Institute of Mental Health, Biological Psychiatry Branch, Bethesda, Maryland 20892, USA.
Dunn
Robert M
RM
Frye
Mark A
MA
Ketter
Terence A
TA
Luckenbaugh
David A
DA
Leverich
Gabriele S
GS
Speer
Andrew M
AM
Osuch
Elizabeth A
EA
Jajodia
Kamal
K
Post
Robert M
RM
D000085:Acetates / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000588:Amines; D000928:Antidepressive Agents / Q000627:therapeutic use*; D018592:Cross-Over Studies; D003430:Cross-Sectional Studies; D003509:Cyclohexanecarboxylic Acids; D004311:Double-Blind Method; D004351:Drug Resistance; D005260:Female; D005544:Forecasting; D000077206:Gabapentin; D006801:Humans; D000077213:Lamotrigine; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000175:diagnosis*; D012008:Recurrence; D012189:Retrospective Studies; D014227:Triazines / Q000627:therapeutic use*; D005680:gamma-Aminobutyric Acid
D000085:Acetates; D000588:Amines; D000928:Antidepressive Agents; D003509:Cyclohexanecarboxylic Acids; D014227:Triazines; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D000077213:Lamotrigine