Smoking cessation and duloxetine toxicity: A case report

Psychiatric medications are among the drugs affected by cigarette smoke, and because of the high prevalence of smoking in the psychiatric community, psychiatric patients are particularly at risk when entering the smoke-free environment of a hospital. Polycyclic aromatic hydrocarbons present in cigarette smoke are well-known inducers of cytochrome P450 (CYP) enzymes. CYP1A2 induction by cigarette smoking increases metabolic clearance of substrates of this enzyme; smoking cessation results in a decrease in CYP1A2 activity, which causes an increase in serum substrate levels. Although these effects are well documented, the effect of smoking cessation remains a hidden danger, in part, because computerized drug interaction surveillance systems are not designed to alert clinicians when an offending agent is discontinued. To raise awareness and demonstrate the importance of a thorough assessment of smoking status, we present a case in which the temporal relationship of smoking cessation to the emergence of nausea, vomiting, and tachycardia 3 days later (day 3); the development of myoclonic jerks by day 5; and the resolution of symptoms on reduction of duloxetine dosage on day 44 implicates duloxetine toxicity in a patient with ischemic cardiomyopathy awaiting implantation of a left ventricular assist device.