Answer
The hormones are absorbed through the skin rather than the stomach, so vomiting or diarrhoea does not directly interrupt absorption. Detachment or interacting medicines can still reduce protection.
Sources for this answer
- NHSNHS · NHS medicine guidance
- EVRA 203 micrograms/24 hours + 33.9 micrograms/24 hours transdermal patch — Current selected SmPCemc · Summary of Product Characteristics