Adverse drug reactions are appreciably harmful or unpleasant reactions resulting from an intervention related to the use of medical products, which predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product. Given medical case reports extracted from MEDLINE, the task is to classify whether the case report mentions the presence of any adverse drug reaction. Classify your answers into non-adverse drug event and adverse drug event.

[EX Q]: Chronic hydroxychloroquine use associated with QT prolongation and refractory ventricular arrhythmia.
[EX A]: adverse drug event

[EX Q]: 2-CdA induces lymphocytopenia, which may explain the improvement in this patient's psoriasis.
[EX A]: adverse drug event

[EX Q]: BACKGROUND: Zidovudine, a Nucleoside Reverse Transcriptase Inhibitor (NRTI) is one of the earliest antiretroviral agents used as a combination in the Highly Active Antiretroviral Therapy (HAART) for the treatment of HIV infection.
[EX A]:
non-adverse drug event