Heart attack patients could be more at risk of a second attack if they are prescribed popular painkillers such as ibuprofen, research has suggested.
Non-steroidal anti-inflammatory drugs (NSAIDs) are associated with a 45% increased risk of death or recurrent heart attack within as little as one week of treatment, researchers found.
During a three-month course of treatment, this increased risk persisted at 55%.
The latest findings support previous research which has highlighted the risks associated with NSAIDs.
In January, experts found that the drugs increase the chances of heart attacks and strokes when taken at high doses or over the long term.
In the most recent study, a team at Copenhagen University in Denmark followed 83,697 heart attack survivors who were aged 68 on average.
Of the participants, 42.3% had been given at least one prescription for an NSAID following their attack.
The most common NSAIDs given on prescription were ibuprofen (23% of the group) and diclofenac (13.4%).
All NSAIDs were associated with an increased risk of death or recurrent heart attack, with diclofenac having the highest risk, the study showed.
Lead author, Anne-Marie Schjerning Olsen, said: "Overall, NSAID treatment was associated with a statistically significant increased risk of death. Our results indicate that there is no apparent safe therapeutic window for NSAIDs in patients with prior heart attack."
The NSAID naproxen was not associated with an increased risk of death or recurrent heart attack.
Dr Olsen said: "A very conservative approach to use NSAIDs in patients with prior heart attack is warranted."
The research was published in Circulation, the journal of the American Heart Association.