Pulseless ventricular tachycardia and ventricular fibrillation are the main causes of sudden cardiac death, but other ventricular tachyarrhythmias can occur without haemodynamic compromise. Ventricular arrhythmias occur mainly as a result of myocardial ischaemia or cardiomyopathies, so risk factors are those of cardiovascular disease.We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of antiarrhythmic drug treatments and defibrillation for use in out-of-hospital cardiac arrest associated with shock-resistant ventricular tachycardia or ventricular fibrillation? What are the effects of antiarrhythmic drug treatments for use in out-of-hospital cardiac arrest associated with shock-resistant ventricular tachycardia or ventricular fibrillation? We searched: Medline, Embase, The Cochrane Library, and other important databases up to May 2007 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).We found 11 systematic reviews and RCTs that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.In this systematic review we present information relating to the effectiveness and safety of the following interventions: bretylium, lidocaine, amiodarone, procainamide, and defibrillation.