Nefazodone overdose

'Atypical' antidepressants in overdose: clinical considerations with respect to safety

The 'atypical' antidepressants comprise a heterogenous class with wide variation in presentation and management during overdose, both when compared with each other and with more traditional agents.Further toxico-epidemiological data are required to make definitive predictions about the clinical effects of most of these agents in overdose. Here, however, we review the available information in a manner intended to benefit both prescribers and clinical toxicologists. Our conclusion is that there can be no generic response by medical practitioners as to the 'safety' of these new antidepressants. Though undoubtedly exhibiting fewer problems in specific areas than some of the older classes of agents (e.g. arrhythmias with tricyclic antidepressants) each nonetheless presents unique safety problems. We experienced great difficulty obtaining accurate information from the manufacturers about the animal toxicity data upon which their recommended human dose limits were set. This highlights the uncertainties involved with too readily making 'safety' claims about these agents. The decision to prescribe 'atypical' antidepressant medications alleged to be both efficacious and safe in overdose involves a medicolegal tension. This tension is between respecting patient autonomy through frank communication of the material risk of overdose and non-disclosure to avoid such harm.

Nefazodone poisoning: toxicokinetics and toxicodynamics using continuous data collection

Nefazodone overdose has been reported infrequently. The commonest effects reported are drowsiness, nausea, dizziness, and vomiting, less commonly hypotension and bradycardia. We report a case of single-agent nefazodone poisoning. Serial drug concentrations were taken for quantification of parent drug and metabolites. Clinical findings were documented every 1 to 2 hours. We modeled both the toxicokinetics of nefazodone and correlated this with clinical effects and electrocardiograph (ECG) abnormalities. A 16-year-old female took 2.4 g of nefazodone. She had significant drowsiness in the first 6 hours, associated with hypotension (systolic BP < 90 mmHg; lowest BP 70/30 mmHg) for 18 hours, and mild bradycardia (slowest rate of 56 bpm). She had a prolonged QT/QTc which normalized over 24 hours. She was given charcoal and intravenous fluids and was observed carefully, recovering with no problems. The terminal elimination half-life for nefazodone was 8.3 hours, and its metabolite hydroxy(OH)-nefazodone was 14.6 hours. BP-time curves demonstrated an 18-hour period of hypotension. There was a significant correlation between systolic BPand OH-nefazodone (R2 = 0.602). HR remained between 56 and 66 bpm for 30 hours despite hypotension. QT was significantly correlated with nefazodone (R2 = 0.911) and OH-nefazodone (R2 = 0.797), but no significant relationship between QTc and drug concentrations. The case demonstrates that nefazodone may potentially cause cardiac toxicity, which appears to be concentration-dependent. Although QT was concentration-dependent, this would need confirmation with other cases. Bradycardia, hypotension, and drowsiness are the most significant effects and are maximal in the first 12 hours when parent and metabolite concentrations are high.

Antidepressants, old and new. A review of their adverse effects and toxicity in overdose

The newer antidepressants are as efficacious as the older agents in the treatment of depression. They have a side effect profile that is different from the older drugs and are generally better tolerated. Drug-drug interactions do exist with some of these agents and can usually be predicted from knowledge of their metabolism. When taken in overdose as the sole agents they are rarely fatal; seizures, nausea, vomiting, decreased level of consciousness, and tachycardia are common. In combination with other drugs, toxicity can be more severe. The serotonin syndrome can occur with many of these drugs, and the emergency physician must be vigilant in the evaluation of the overdose patient. CAs and older MAOIs are still in use and remain dangerous when taken in overdose. Patients asymptomatic after a period of observation in the ED usually can be discharged after psychiatric evaluation, when it is required.