Antihypertensive drugs and the risk of idiopathic aplastic anaemia

Aims A recent report has raised concern that nifedipine may be associated w ith an increased risk of aplastic anaemia. This large population-based stud y evaluated the risk of idiopathic aplastic anaemia in users of calcium cha nnel blockers compared with that of other antihypertensive drugs. Methods The study was based on information derived from the General Practic e Research Database. We conducted a follow-up study with a nested case-cont rol analysis of 322 448 subjects who received antihypertensive drugs. Cases were people who had a first-time diagnosis of aplastic anaemia during Janu ary 1, 1988 through September 30, 1997. The risk estimate of aplastic anaem ia was calculated for all antihypertensive drugs. For the nested case-contr ol analysis, six controls were matched to each case on age, sex and general practice attended. Odds ratios compared the risk of idiopathic aplastic an aemia for all antihypertensive drugs relative to nonusers. Results There were 13 cases of newly diagnosed idiopathic aplastic anaemia. The estimated risk of aplastic anaemia per 100 000 users was 0.8 (95% CI 0 .1, 4.7) for calcium channel blockers, 1.4 (95% CI 0.5, 4.1) for beta-adren oceptor blockers, 2.3 (95% CI 0.6, 8.6) for angiotension-converting enzyme (ACE) inhibitors and 5.9 (95% CI 1.6, 21.5) for users of other antihyperten sive drugs. In the case-control analysis of 13 cases and 77 controls, the o dds ratio was 0.3 (95% CI 0.02, 3.3) for calcium channel blockers, 0.5 (95% CI 0.1, 2.5) for beta-adrenoceptor blockers, 0.7 (95% CI 0.1, 5.6) for ACE inhibitors, 1.2 (95% CI 0.1, 11.8) for users of other antihypertensive dru gs and 0.7 (95% CI 0.1, 7.2) for users of multiple drugs with a calcium cha nnel blocker compared with nonusers. Conclusions The present study suggests that the use of calcium channel bloc kers is not associated with an increased risk of aplastic anaemia.