In a case where a patient has a WBC count of 1.0 x 10^9/L after starting a new medication, what medication is the patient likely taking?

Clozapine is known for its potential to induce agranulocytosis, which is a significant reduction in the white blood cell (WBC) count. This side effect is particularly concerning because it can increase the risk of infection due to the body’s decreased ability to combat pathogens. Patients on clozapine require regular monitoring of their complete blood count (CBC) to ensure their WBC levels remain within safe limits.

In contrast, while other medications, including atypical antipsychotics like risperidone and haloperidol (a typical antipsychotic), can have side effects, they are not typically associated with causing such a drastic drop in white blood cell counts. Atypical antidepressants also do not commonly induce significant changes in WBC counts like clozapine does.

Thus, the scenario presented—where the patient has a low WBC count after starting a new medication—points towards clozapine as the likely culprit due to its notorious side effect profile. Regular hematological monitoring is crucial in patients receiving this medication to prevent severe complications related to decreased white blood cell counts.