Rationale: Occupancy of dopamine D2 receptors by antipsychotic drugs depends on the individual availability of D2 receptors and on the dose and type of antipsychotic medication. It has been suggested that a low availability of these receptors may increase the risk for addictive behavior.
Objective: This study aims to show that patients with relatively high occupancy of D2 receptors by antipsychotic drugs are more prone to nicotine consumption.
Methods: Striatal D2 receptor occupancy by equivalent doses of olanzapine or risperidone was assessed with [123I]iodobenzamide single-photon emission computed tomography (SPECT) in 36 patients with schizophrenia. Smoking status at the time of SPECT imaging was assessed. The number of cigarettes used in the following three consecutive years was estimated with the Life Chart Schedule (LCS).
Results: There was a positive and significant relation between D2 receptor occupancy following treatment with olanzapine (n=19) or risperidone (n=12) and the number of cigarettes smoked in three consecutive years (r=0.60, p<0.001) in patients who smoked. There was a significant difference in the percentage of D2 occupancy for smokers (mean 74.3%, SD 12.8, n=31) and nonsmokers (mean 49.8%, SD 9.1, n=5).
Conclusion: Frequency of cigarette smoking in schizophrenic patients treated with antipsychotic medication is significantly and negatively related to the availability of striatal D2 receptors.