Iodine-123-iodobenzamide binding in parkinsonism: reduction by dopamine agonists but not L-Dopa.
The aim of the present study was to investigate the effect of treatment with L-Dopa or a dopamine agonist, or both, on specific striatal 123I-iodobenzamide (IBZM) binding using an intraindividual longitudinal design.


METHODS
We prospectively studied the effect of dopaminomimetic treatment on specific [123I]IBZM binding measured by SPECT in 29 patients with a clinical diagnosis of Parkinson's disease, none of whom had previously received dopaminomimetic drugs. The patients had been selected on the basis of normal subsequent specific [123I]IBZM binding, semiquantitatively calculated as the basal ganglia/frontal cortex ratio, and a positive response to the dopamine agonist apomorphine before initiation of dopaminomimetic therapy. A second 123I-IBZM SPECT investigation was performed after 3-6 mo of treatment with L-Dopa or a dopamine agonist, or both.


RESULTS
Specific [123I]IBZM binding was unchanged in 10 patients treated with L-Dopa alone. However, after treatment with a dopamine agonist there was a significant decline in specific [123I]IBZM binding (p < 0.05). After treatment with a combination of L-Dopa and a dopamine agonist, specific [123I]IBZM binding was reduced without reaching a level of significance (p = 0.08).


CONCLUSIONS
Short-term treatment with a dopamine agonist but not with L-Dopa reduces specific [123I]IBZM binding. Therefore, before performing an [123I]IBZM SPECT scan in patients previously treated with dopaminomimetic drugs, dopamine agonists should be discontinued.
Schwarz
J
J
Department of Neurology, Klinikum Grosshadern, Ludwig Maximilians University, Munich, Germany.
Oertel
W H
WH
Tatsch
K
K
D000978:Antiparkinson Agents / Q000627:therapeutic use*; D001549:Benzamides / Q000493:pharmacokinetics; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism; D016022:Case-Control Studies; D003287:Contrast Media; D018491:Dopamine Agonists / Q000627:therapeutic use*; D018492:Dopamine Antagonists / Q000493:pharmacokinetics; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use*; D008875:Middle Aged; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D011446:Prospective Studies; D011759:Pyrrolidines / Q000493:pharmacokinetics; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon
D000978:Antiparkinson Agents; D001549:Benzamides; D003287:Contrast Media; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D011759:Pyrrolidines; D007980:Levodopa; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide