Commonly used heart drug may up cardiac arrest risk

Sudden cardiac arrest is lethal in minutes if untreated

A drug commonly used to treat high blood pressure and chest pain may increase the risk of sudden cardiac arrest, a study has found. Sudden cardiac arrest is lethal in minutes if untreated. The study examined if nifedipine and amlodipine, dihydropyridines widely used for high blood pressure and angina, are linked with out-of-hospital cardiac arrest. The nifedipine doses most often used and studied in this investigation are 30 milligrammes (mg) and 60 mg and the amlodipine doses are 5 mg and 10 mg.

Standard practice is to start with a lower dose, then give the higher dose if blood pressure or chest pain are not sufficiently reduced. “The findings need to be replicated in other studies before action should be taken by doctors or patients,” said Hanno Tan, a cardiologist at the Academic Medical Centre in the Netherlands.

Patients with out-of-hospital cardiac arrest due to ventricular fibrillation/tachycardia were enrolled, plus up to five controls per patient matched for age and sex. Current use of high-dose (60 mg/day), but not low-dose (less than 60 mg/day), nifedipine was significantly associated with an increased risk of out-of-hospital cardiac arrest compared to non-use of dihydropyridines, with an odds ratio of 1.5 in ARREST and 2.0 in DANCAR.

High-dose nifedipine was also associated with an increased risk of out-of-hospital cardiac arrest when compared with any dose of amlodipine, with odds ratios of 2.3 and 2.2 in the ARREST and DANCAR registries, respectively.

There was no risk associated with amlodipine. “Nifedipine and amlodipine are often used by many cardiologists and other physicians, and the choice often depends on the prescriber’s preference and personal experience,” said Tan. “Both drugs are generally considered to be equally effective and safe and neither has been associated with sudden cardiac arrest,” he said. “This study suggests that high-dose nifedipine may increase the risk of sudden cardiac arrest due to fatal cardiac arrhythmia while amlodipine does not. If these findings are confirmed in other studies, they may have to be taken into account when the use of either drug is considered,” he added.

These findings may be surprising given that both drugs have been in use for many years and in many patients, researchers said. A possible explanation why this discovery has only been made now is that out-of-hospital cardiac arrest is very difficult to study due to its rapid course, and requires dedicated datasets collected specifically for this purpose.