Calcium antagonists: the current controversy
- Robert F.W. Moulds
- Aust Prescr 1996;19:35
- 1 April 1996
- DOI: 10.18773/austprescr.1996.027
Most practitioners will be aware of the current vigorous debate about the use of calcium antagonists in a wide range of clinical situations.
Some of the issues are not new, but the catalyst for the recent debate has been the publication of a case control study from the U.S.A.1 This compared patients who had suffered a myocardial infarction with those who had not, with respect to their prior use of various antihypertensive drugs. The study reported that the risk of myocardial infarction was significantly increased in patients treated with a calcium antagonist compared with those treated with a diuretic.
In the light of the undoubted benefits of calcium antagonists in lowering blood pressure in hypertensive patients and improving angina in patients with coronary heart disease, it is unlikely a single case control study would have provoked such concern if it were not for the fact that calcium antagonists can be harmful in some specific circumstances. Thus, might it be that they could be harmful in broader circumstances than previously suspected?
Issues which are particularly relevant to the current controversy are:
Obviously, a major factor in the current debate is the fact that the overall market for calcium antagonist drugs is one of the largest for any drug group e.g. the cost to the Pharmaceutical Benefits Scheme in Australia for calcium antagonists in the financial year 1994/95 was approximately $124.6 million. Thus, the pharmaceutical industry has a major financial interest in the outcome of the current debate. In addition, most major cardiovascular research groups in the world receive large research grants from the pharmaceutical industry, thus raising questions about the objectivity of opinions expressed by the leaders of those research groups.
In the face of such controversy, it is difficult for individual practitioners to decide what to do. At present, there is consensus that there is not a strong case for stopping calcium antagonist treatment for patients in whom it has been apparently successful. Current guidelines3 for the initiation of treatment for either hypertension or angina also do not recommend calcium antagonists as first-line treatment and, in the case of the dihydropyridine calcium antagonists, emphasise the advisability of concurrent treatment with a beta blocker. If current guidelines in Australia relating to the use of calcium antagonists are followed, it is unlikely patients will be ill served.
Department of Clinical Pharmacology and Therapeutics, Royal Melbourne Hospital, Melbourne