Scientists say they have a new weapon in the fight to prevent patients having repeated heart attacks.
The drug can prevent people suffering more heart attacks
They say the drug valsartan could help the third of patients who cannot take the existing drugs.
A study in the New England Journal of Medicine showed valsartan was as effective as the drug usually given to heart attack patients.
Fourteen thousand heart attack patients in 24 countries took part in the worldwide study.
All the patients were also on other medication such as aspirin, statins or beta blockers.
The study was designed to compare valsartan - which is given to patients with blood pressure problems, but which is not yet licensed for use in heart attack patients - with an ACE inhibitor, the standard treatment, called captopril.
ACE inhibitors are the standard drugs given to patients who have had heart attacks to prevent them becoming ill again.
However, around 30% of patients cannot or do not take the drugs, often because of side effects, such as a persistant cough.
In the study, just over 4,900 were given valsartan, another 4,900 were given captopril, and the remaining group were given a combination of the two.
Patients were followed up for two years.
In the group taking valsartan, there were 979 deaths, among those taking the ACE inhibitor there were 958.
In the group of patients taking both drugs, there were 941 deaths.
Just over 20% of patients taking either valsartan or captopril stopped taking their medication during the trial.
In the captopril group, the most common side effects reported were cough, rash and taste problems.
Among patients taking valsartan, low blood pressure and kidney problems were the main problems.
ACE inhibitors, or angiotensin-converting-enzyme inhibitors, are used to reduce high blood pressure, and to treat congestive heart failure in heart-attack patients.
Valsartan is an angiotensin receptor blocker - so it works on thr same chemical pathway, but in a slightly different way.
Around 275,000 people in the UK have heart attacks each year - almost 57,000 are fatal.
Patients who survive have a 10% risk of having another heart attack within a year, although taking medication can cut this risk by a quarter.
Writing in the New England Journal of Medicine, the researchers led by Dr Marc Pfeffer of the Brigham and Women's Hospital in Boston, Massechussetes, said valsartan should be considered a "clinincally effective alternative" to captopril.
They added: "The choice between these alternative treatments will depend on cumulative clinical experience, tolerability, safety convenience and cost."
Professor Michael Frennaux, head of cardiology at the University of Wales College of Medicine, told BBC News Online: "The message is not that this is a better drug.
"This drug offers another choice, and that means that you have an option for people who aren't on, or cannot take ACE inhibitors."
Eve Knight of the British Cardiac Patients Association said it was crucial for patients to have another option if they could not take ACE inhibitors.
"I cannot emphasise enough the importance of choice.
"If you can't take an ACE inhibitor, you're more likely to have a second heart attack or to have heart failure.
"It's really important you have 'another tool in the box'."