Objectives: The incidence of cardiovascular diseases is increasing and there is a growing need to provide access to quality cardio drugs in Africa. In the SEVEN study, we analysed 1530 cardiovascular drug samples randomly collected from 10 African countries. By that time, of the seven drugs products analysed, only those containing amlodipine and captopril had very low assay values with active substance contents that could be less than 75% of those expected. In this article we investigate complementary aspects of the amlodipine and captopril samples so to explain the previously observed low assays for these two drugs. Design: Post hoc analysis of the captopril and amlodipine drugs samples and their packages collected in the context of the SEVEN study. Setting: 10 countries were concerned: Benin, Burkina Faso, Congo, Democratic Republic of the Congo, Guinea, Côte d'Ivoire, Mauritania, Niger, Senegal and Togo. Participants: Local scientists and hospital practitioners collected the drug samples in the 10 African countries. Outcome measures: The drug amount and the relative amounts of drug impurities, as well as the main compounds of the drugs packaging, were analysed. Results: Identification of the blister packaging of the samples led to separate both amlodipine and captopril drug samples in two groups. Mann Whitney's bilateral test showed a significant difference (p<0.0001) between the median value of the captopril dosage when tablets are packaged in blisters providing higher protection to humidity (n=105) as opposed to the tablets packaged in blisters providing lower humidity protection (n=130). Conclusion: Based on these results, particular attention should be paid to the materials and types of packaging used in order to minimise the lack of control over the exposures and drug circuits present in these different countries.