Citalopram overdose: Late presentation of torsades de pointes (TDP) with cardiac arrest

Citalopram in overdose can cause QT sub(c) prolongation that predisposes to torsades de pointes (TDP). Cardiac conduction delays are expected within 24 hours of exposure and may be due to the metabolite didesmethylcitalopram. We report a first case of delayed citalopram induced TDP with documented serum levels and recorded ECGs. A 36 year old woman with a history of multiple suicide attempts, depression, alcoholism, anorexia, and psoriasis, presented 36 hours after ingesting 1000 mg of citalopram with 2 quarts of wine. Ingestion occurred in the PM on day 1. During day 2, she felt nauseated, weak, and lethargic. She visited her parents in the afternoon, but returned home early and went to the bed. On the morning of day 3, she had palpitations and numbness in both the arms that prompted her visit to the ED. Vital signs were: BP, 84/44 mmHg; T, 99.3 degree F; P, 102-160/min; RR, 17/min; O sub(2), Sat 99% RA. An ECG had intermittent runs of wide complex tachycardia with a QT sub(c) of 600 msc. Her Mg super(2+) level was 2.5 mg/dL. The patient was started on O sub(2), IV NaCl and was given MgSO sub(4) (2 g IV). She developed bigeminy, and despite IV lidocaine intermittent TDP occurred. An isoproterenol infusion was started and she converted to sinus rhythm. Additionally, she received KCl, K sub(3)PO sub(4), and a transvenous pacemaker. 24 hours later her ECG showed normal sinus rhythm with a QT sub(c) of 529 msec. The QT sub(c) interval narrowed to 442 msec at 48 hours. A citalopram level was 477 ng/mL (therapeutic: 40-110 ng/mL) and desmethylcitalopram was 123.2 ng/mL (therapeutic: 14-40 ng/mL). Clinicians should be aware of the possibility for delayed and prolonged cardiac toxicity of citalopram.