D-2 RECEPTOR BLOCKADE BY FLUNARIZINE AND CINNARIZINE EXPLAINS EXTRAPYRAMIDAL SIDE-EFFECTS - A SPECT STUDY

Twenty-six patients under treatment with the calcium channel blockers flunarizine (Fz) or cinnarizine (Cz) were examined with single-photon emission computed tomography using [I-123]iodobenzamide as a ligand. T he striatal dopamine D-2 receptor-binding potential was determined and found to be reduced by 14 to 63% (39.5 +/- 15.0%; p < 0.0001) in pati ents compared with age-matched control values. This reduction was larg er in 12 patients with extrapyramidal symptoms and was only slowly rev ersible after discontinuation of treatment. Patients treated for >6 mo nths had significantly larger reductions than patients treated for a s horter period. Parkinsonian symptoms were only seen in patients older than 50 years. Our findings prove a neuroleptic-like action of Fz and Cz, which seems to be the major reason for their extrapyramidal side e ffects. Older age and long-term treatment are predisposing factors for these effects.