a result produced by an action. additive effect the combined effect produced by the action of two or more agents, being equal to the sum of their separate effects. adverse effect a symptom produced by a drug or therapy that is injurious to the patient. Bainbridge effect Bainbridge reflex. Bohr effect decreased affinity of hemoglobin for oxygen caused by an increase of carbon dioxide; the oxyhemoglobin dissociation curve is displaced to the right because of higher partial pressure of carbon dioxide and lower pH.