FDA Safety Alert: Montelukast May Cause Serious Mental Health Side Effects 6 Mar, 2020 | 10:22h | UTC FDA requires Boxed Warning about serious mental health side effects for asthma and allergy drug montelukast (Singulair); advises restricting use for allergic rhinitis – U.S. Food & Drug Administration (free) Commentary: Montelukast to Get Boxed Warning – NEJM Journal Watch (free)