A widely prescribed painkiller, diclofenac, has been linked to a 50 percent increased risk of heart attack or stroke even at low doses, alarming new research suggests. The study also found heightened risks of heart failure and irregular heartbeat across all ages in both men and women.

Previously available over the counter, diclofenac was reclassified in the UK as prescription-only due to serious side effect concerns. Commonly used for headaches, back pain, arthritis, and flu symptoms, the drug was subject to this change in January 2015 by the Medicines and Healthcare products Regulatory Agency, which cited a "small but increased" risk of heart issues.

The extensive research involving over six million people is considered the largest of its kind, associating the drug with "major cardiovascular events". Cardiologist Dr Morten Schmidt from Aarhus University Hospital in Denmark highlighted the cardiovascular dangers of diclofenac compared to non-use, paracetamol, and other traditional non-steroidal anti-inflammatory drugs.

In his BMJ article, Dr Schmidt advocates for prescription-only access to diclofenac, as is the case in the UK, and stresses the need for clear warnings on packaging. His team's findings indicate that users of diclofenac, often sold under the brand name Voltarol, face a higher likelihood of experiencing heart-related health issues.

Patients using diclofenac saw a staggering 50 percent increase in rates of health complications after just 30 days compared to those not on any medication. Additionally, there was a 20 percent rise when pitted against ibuprofen or paracetamol users, and a worrying 30 percent jump in contrast with individuals on naproxen, reports Surrey Live.

As Dr Schmidt emphatically put it: "It is time to acknowledge the potential health risk of diclofenac and to reduce its use."

Commonly prescribed within the UK, with five million prescriptions annually, diclofenac belongs to the NSAIDs group, but unlike other traditional NSAIDs, its cardiovascular risks have not been scrutinized in large controlled trials due to ethical concerns.

Dr Schmidt and colleagues cleverly utilised national registry data from more than 6.3 million middle-aged adults in Denmark for an observational study spanning two decades from 1996 to 2016. This allowed them to associate starting diclofenac with increased risks of arrhythmia, stroke, heart failure, and heart attacks – alarmingly more so than even taking no NSAIDs.

To make matters worse, starting this painkiller also signaled higher chances of cardiac death and severe internal bleeding within the upper intestines.

Dr Schmidt has emphasised, "Treatment of pain and inflammation with NSAIDs may be worthwhile for some patients to improve quality of life despite potential side effects. Considering its cardiovascular and gastrointestinal risks, however, there is little justification to initiate diclofenac treatment before other traditional NSAIDs."

Although the absolute risk of heart attack, stroke, or other cardiovascular issues remains low for individual patients, researchers caution that no concrete conclusions on causation can be drawn from this observational study. Nonetheless, given the vast sample size surpassing many previous collective research efforts, the findings lend significant weight to clinical judgements.

The MHRA warns against the use of diclofenac by those with serious heart conditions. It advises people who have experienced heart failure, heart disease, or stroke, as well as smokers and individuals with high blood pressure, elevated cholesterol levels, or diabetes, to seek medical advice before using the medication.

The MHRA says diclofenac will continue to be a safe and effective form of pain relief, except for patients in specific "at risk" groups. A significant study from Oxford University in 2013 disclosed that out of every 1,000 people with a moderate risk of heart disease taking 150mg daily for a year, roughly three could endure an avoidable heart attack, with one case being fatal.

Following this, European health officials have reviewed the findings, advising that individuals who have heart conditions or past instances of heart attacks or strokes should no longer use diclofenac. Additionally, diclofenac can provide short-term relief from dental pain and menstrual cramps by inhibiting a body chemical known as cyclo-oxygenase, which generates substances in reaction to injury, leading to pain, swelling, and inflammation.