In general, there is no significant interaction when consuming amphetamine with food, but the pH of gastrointestinal content and urine affects the absorption and excretion of amphetamine, respectively.[144] Acidic substances reduce the absorption of amphetamine and increase urinary excretion, and alkaline substances do the opposite.[144] Due to the effect pH has on absorption, amphetamine also interacts with gastric acid reducers such as proton pump inhibitors and H2 antihistamines, which increase gastrointestinal pH (i.e., make it less acidic).[144]