Common side effects include tiredness, loss of appetite, diarrhea, abdominal pain, hiccups, itchiness, pneumonia, and blood pressure changes.[1] Other severe side effects may include anaphylaxis.[1] While use in pregnancy does not appear to be harmful, such use has not been well studied.[2] Aprepitant belongs to the class of neurokinin-1 receptor antagonists medications.[1] It works by blocking substance P from attaching to the NK1 receptors.[3]