In a story reminiscent of the history of aspirin, two other groups of drugs - ACE inhibitors and statins - appear to have effects beyond those for which they originally received a licence.
Just as aspirin has progressed from being a mere pain reliever to an agent that prevents heart attacks and strokes, ACE inhibitors are now known to have a much wider range of benefits in protecting against cardiovascular disease.
The latest studies of ACE inhibitors - which have been used to treat blood pressure for 20 years - show they can prevent heart attack, stroke and diabetes in a variety of patients.
ACE inhibitors also appear to be able to slow muscle decline in the elderly and reduce the risk of dementia following recent stroke.
ACE stands for angiotensin converting enzyme and the drugs work by blocking the pathway that creates angiotensin II, the most active form of the substance. It is part of a cascade of proteins produced by the body when it senses that blood pressure is too low. It constricts the vessels, which is ideal if someone has a severe bleeding injury but not so good when too much angiotensin causes a chronic rise in blood pressure (the narrowed arteries provide more resistance to the pumping action of the heart).
In addition to its effects on blood pressure, doctors have discovered other undesirable long-term effects of angiotensin. It promotes the build-up of plaques in the arteries, encourages blood clotting and increases the enlargement of heart muscle after a heart attack. How it actually does this is unclear, although an inflammatory action in body tissue seems likely.
According to Dr Salim Yusuf, director of cardiology at McMaster University in Canada, blood pressure lowering is only part of the story of how ACE inhibitors prevent cardiovascular disease. In a commentary in the Lancet last month, commissioned to coincide with the publication of another landmark study confirming increased benefits for cholesterol-lowering drugs, Yusuf said: "The implications of the Heart Protection Study are profound. Cholesterol lowering with a statin is of value in much broader populations than currently recognised, including those with low and normal cholesterol levels. Practically all patients with vascular disease today in Western countries will benefit from statins".
The study which provoked such a profound statement showed that people with diabetes or arterial disease who took 40 mg of Simvastatin for five years had a one-third reduction in the risk of heart attack and stroke, compared to those given a placebo or dummy pill. It also found that the benefits of statins were additional to other cardiac protective treatments such as aspirin, beta blockers and ACE inhibitors. While it stopped short of recommending a "statin for all" policy, the fact that the drugs produce a benefit in people with normal or low cholesterol levels suggests a mechanism of action which goes beyond a cholesterol-lowering effect. Dr Yusuf has calculated that aspirin, beta blockers, ACE inhibitors and lipid-lowering drugs have the potential to reduce future heart attack or stroke by 25 per cent each. If all four drugs are used together, he reckons the cumulative risk reduction is 75 per cent.
While these figures are impressive for the wider population, what do they mean for the individual? And what about side-effects, especially for a patient who feels well and for whom these drugs offer a potential rather than immediate benefit? The Heart Protection Study suggests if 1,000 people take Simvastatin for five years, 70 to 100 will avoid having a heart attack or stroke.
From a sideeffect perspective, the results were good. While statins are known to cause an elevation in liver enzymes (reflecting inflammation), in this study a persistent elevation was found in less than 0.1 per cent of patients. Muscle inflammation can also occur; although 6 per cent of participants reported muscle pain or weakness, evidence of muscle breakdown was found in only five out of 10,000 patients given Simvastatin 40mg a day.
However, the recent withdrawal of another statin - Cerivastatin - on safety grounds emphasises the importance of using specific drugs at doses proven to be both safe and effective when considering such treatment. Incidentally, the principal side-effect of ACE inhibitors is a cough, which is reported by about 15 per cent of patients taking this class of drug.
For a smoker with established heart or vascular disease, quitting smoking and using a combination of preventative drugs offers a significant potential benefit in terms of avoiding future heart attack or stroke. We have come a long way since the 1950s, when these diseases were not considered preventable. Some 50 years later, even those with established vascular problems are being offered a real second chance.