Drug General Information (ID: DDIEZGRXYS)
Drug Name			Levothyroxine		Drug Info		Ferrous gluconate		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antithyroid Agents				Iron Supplement
Structure

Mechanism of Levothyroxine-Ferrous gluconate Interaction (Severity Level: Moderate)
Complex formation Click to Show/Hide Mechanism Graph
Drug Name		Levothyroxine				Ferrous gluconate
Mechanism		Binds to polyvalent cations				Polyvalent cations
Key Mechanism Factor 1
		Factor Name		Chelation
		Factor Description		Chelation is a direct drug interaction that usually involves the formation of dimers or trimers, resulting in larger complexes and poorer absorption.
Mechanism Description		Decreased absorption of Ferrous gluconate due to formation of complexes caused by Levothyroxine

Recommended Action
Management		Some experts recommend separating the times of administration of levothyroxine and iron-containing preparations by at least 2 to 4 hours. Monitoring of serum TSH levels is recommended. Patients with gastrointestinal or malabsorption disorders may be at a greater risk of developing clinical or subclinical hypothyroidism due to this interaction.

References
1	Campbell NR, Hasinoff BB, Stalts H, Rao B, Wong NC "Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism." Ann Intern Med 117 (1992): 1010-3. [PMID: 1443969]