Compulsive Biting and Chewing with Mixed Amphetamine Salts: A Case Report.

Stimulants are the first-line pharmacological treatment for attention deficit hyperactivity disorder (ADHD). We present the unique case of a patient who developed a chewing compulsion when taking mixed amphetamine salts (MAS). A 32-year-old female patient with a past medical history of gastroesophageal reflux disease (GERD), gastroparesis, and migraines was seen for initial psychiatric assessment due to concerns for irritability. She was diagnosed with post-traumatic stress disorder (PTSD); generalized anxiety disorder; ADHD, inattentive type; and unspecified bipolar disorder. Lamotrigine was started and titrated to 25mg twice per day, with improved mood stability. MAS immediate-release (IR) was started at 2.5mg and titrated to 5mg daily for ADHD. She then experienced an uncontrollable urge to chew, finding relief when chewing on a child's teething necklace, which provided satisfaction and a reduction in anxiety. She denied jaw tightness or teeth grinding. The dose of MAS IR was reduced to 2.5mg daily with improvement in symptoms and later increased again to 5mg daily, which she was then able to tolerate. Stereotyped biting behaviors have been observed in rats with the use of amphetamines, and the onset of compulsive behavior has emerged in children with the use of dextroamphetamine. However, this is the first known case of compulsive chewing or biting movements reported in humans with MAS use. This case highlights the need to assess patients for adverse events, such as compulsive biting and chewing movements or other oral facial stereotypies, after commencement of stimulants, including MAS.