= Solution
\b[Use a concurrent randomized comparison of the new leaflet with the existing release information.] Random allocation makes the groups comparable in <expectation> and avoids attributing a secular change in drug supply, release populations or post-release services to the leaflet. Both arms should use the same outcome ascertainment and two-week follow-up. This improves the causal interpretation over a historical before-and-after comparison; adequate sample size remains necessary given the low <statistical power> calculated above. If contamination prevents individual allocation, a carefully designed cluster <randomized controlled trial> is an alternative, with its sample-size calculation allowing for within-cluster dependence.
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