To the Editor The meta-analysis reported by Lasserson et al provides evidence that half of the effect of antihypertensive treatment on blood pressure takes place within the first week of treatment.1 There is no reason to doubt these findings. However, the analysis does not support the conclusion that ‘estimation of maximal effect could be made between 1 and 2 weeks after initiation of antihypertensive therapy’. Nor does it support the view that ‘this knowledge will guide practitioners in deciding when a newly started antihypertensive agent can be judged to be ineffective’.

First, it is not possible to determine whether blood pressure has been reduced by treatment within a week. The authors reached their conclusion after a meta-analysis of measurements in 4168 individual patients. But clinicians must decide whether a newly started antihypertensive agent is ineffective on the basis of measurements …