1. An unwanted or harmful response to a substance, medication, food, or stimulus
The patient experienced an adverse reaction to the antibiotic and had to switch medications.
O paciente teve uma reação adversa ao antibiótico e precisou trocar de medicamento.
2. A negative or unfavorable response or consequence
The policy change received an adverse reaction from the community.
A mudança de política recebeu uma reação adversa da comunidade.