Levothyroxine (Synthroid, Tirosint, Levoxyl) is a medication for treating hypothyroidism (underactive thyroid), a condition that is more common in people with Down syndrome. Health care providers usually recommend taking levothyroxine with water NAC for Thyroid Health Dr. Izabella Wentz, Pharm D Glutathione & Thyroid Health: The Master Antioxidant Levothyroxine Interactions: Drugs, Diet, & More GoodRx Send this to someone who always travels really well. Incorporating these four supplements into your travel routine helps you maintain essential vitamin and nutrient levels to fully embrace each day