Researchers have found a possible safety concern involving nifedipine, a common medicine used to treat high blood pressure and chest pain.
The study suggests that people taking a high daily dose may have a greater risk of sudden cardiac arrest than people using a similar medicine.
Nifedipine belongs to a family of medicines known as calcium channel blockers. These drugs relax blood vessels and make it easier for the heart to pump blood, which can lower blood pressure and reduce some types of chest pain.
High blood pressure is extremely common and can quietly damage the heart, brain, kidneys and blood vessels over many years. Medicines that control it can therefore prevent serious problems such as heart attacks and strokes.
The researchers focused on sudden cardiac arrest, which is different from a heart attack. During cardiac arrest, the heart suddenly stops pumping blood effectively, causing the person to collapse, lose consciousness and stop breathing normally.
Without rapid treatment, cardiac arrest can be fatal within minutes. Immediate cardiopulmonary resuscitation, or CPR, and the use of a defibrillator can greatly improve a person’s chance of survival.
To investigate whether commonly used medicines might influence this risk, researchers compared nifedipine with amlodipine. Both medicines are calcium channel blockers and are widely prescribed for similar heart and blood pressure problems.
The first part of the research used information from the Amsterdam Resuscitation Studies, known as ARREST, in the Netherlands. The researchers examined more than 2,500 people who experienced sudden cardiac arrest and compared them with more than 10,000 people who had not experienced one.
A concerning pattern appeared among people taking nifedipine at a dose of 60 milligrams per day. This higher dose was associated with an increased risk of sudden cardiac arrest, while amlodipine was not linked to the same increase.
The researchers then tested their finding using a separate collection of health information from Denmark. This analysis included more than 8,000 people who experienced sudden cardiac arrest and around 40,000 people used for comparison.
The Danish data showed a similar pattern. Once again, higher-dose nifedipine was associated with a greater risk, giving the researchers more confidence that the finding deserved further investigation.
Laboratory work offered a possible explanation. The researchers found that nifedipine at higher concentrations could affect the electrical activity of heart cells more strongly than amlodipine, potentially making dangerous abnormal heart rhythms more likely in susceptible people.
However, an association in this type of study does not prove that nifedipine directly caused cardiac arrest in every case. Other differences between patients may influence risk, and further research is needed to understand which people might be most vulnerable.
The findings also do not mean that patients should suddenly stop taking nifedipine. Stopping blood pressure medicine without medical advice can allow blood pressure to rise and may create its own serious health risks.
People who take nifedipine, particularly those prescribed higher doses, can discuss the findings with their doctor or pharmacist if they are concerned. A health professional can consider the person’s dose, medical history, other medicines and overall heart risk before deciding whether any change is appropriate.
The research was published in the European Heart Journal and involved data from the Dutch ARREST registry and the Danish Cardiac Arrest Registry. The study highlights why medicines that have been used for many years still need continued safety research as larger and better health databases become available.
For many patients, nifedipine remains a useful medicine for controlling high blood pressure or chest pain. The new findings provide doctors with additional information to consider rather than a reason for patients to abandon an effective treatment on their own.
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