Acute and subchronic effects of amitriptyline on processing capacity in neuropathic pain patients using visual event-related potentials: preliminary findings.
BACKGROUND
Little is known about the effects of low doses of amitriptyline, prescribed in the treatment of neuropathic pain, on attentional processing capacity.


OBJECTIVE
Changes due to amitriptyline treatment on attentional processing capacity were investigated on behavioral measures and event-related brain potentials (ERPs) in six patients with neuropathic pain.


METHODS
Patients were treated for 15 consecutive days with 25 mg nocturnally administered amitriptyline or placebo in a double-blind crossover randomized design. Measurements were carried out on day 1 and day 15 of each treatment period. An attentional capacity probe task was used in which the difficulty level was manipulated, resulting in an easy and a hard condition, while task-irrelevant visual probes were presented. During task performance, ERPs were measured from the midline electrodes Fz, Cz, Pz, and Oz.


RESULTS
Amitriptyline increased reaction times (RTs) after acute but not after subchronic administration. ERP analyses showed that P3 amplitudes to the task stimuli were not affected by amitriptyline in either treatment phase. Moreover, P3 amplitudes to the probes were increased in the easy compared to the hard task condition after subchronic amitriptyline treatment, indicating beneficial effects of repeated amitriptyline administration. In contrast, acute amitriptyline administration did reduce an earlier visual evoked potential, N1, preceding the P3 component.


CONCLUSIONS
The results suggest that amitriptyline, even at low dosages of 25 mg, affects performance after acute administration in chronic neuropathic pain patients. After 2 weeks of treatment, performance appears to be unaffected. No deficits in processing capacity due to amitriptyline treatment were found.
Veldhuijzen
D S
DS
Department of Psychopharmacology, Utrecht Institute for Pharmaceutical Sciences, Rudolf Magnus Institute of Neuroscience, University of Utrecht, P.O. Box 80082, 3508 TB, Utrecht, The Netherlands. D.S.Veldhuijzen@pharm.uu.nl
Kenemans
J L
JL
van Wijck
A J M
AJ
Olivier
B
B
Kalkman
C J
CJ
Volkerts
E R
ER
D000328:Adult; D000639:Amitriptyline / Q000494:pharmacology*; D000928:Antidepressive Agents / Q000494:pharmacology*; D001288:Attention / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects; D005074:Evoked Potentials, Visual / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology / Q000523:psychology*; D010147:Pain Measurement / Q000187:drug effects; D010523:Peripheral Nervous System Diseases / Q000150:complications*; D011930:Reaction Time / Q000187:drug effects
D000928:Antidepressive Agents; D000639:Amitriptyline