Drug General Information (ID: DDIGZ2J4YS)
Drug Name			Calcium carbonate		Drug Info		Thyroid, porcine		Drug Info
Drug Type		Small molecule				Hormones
Therapeutic Class		Antacids/Minerals And Electrolytes				Thyroid Drugs

Mechanism of Calcium carbonate-Thyroid, porcine Interaction (Severity Level: Moderate)
Complex formation Click to Show/Hide Mechanism Graph
Drug Name		Calcium carbonate				Thyroid, porcine
Mechanism		Polyvalent cations				Binds to 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 Calcium carbonate due to formation of complexes caused by Thyroid, porcine

Recommended Action
Management		Some experts recommend separating the times of administration of levothyroxine and calcium-containing preparations by at least 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	Csako G, McGriff NJ, Rotman-Pikielny P, Sarlis NJ, Pucino F "Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders." Ann Pharmacother 35 (2001): 1578-83. [PMID: 11793625]
2	Neafsey PJ "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse 22 (2004): 338-9. [PMID: 15131426]
3	Singh N, Singh PN, Hershman JM "Effect of calcium carbonate on the absorption of levothyroxine." JAMA 283 (2000): 2822-5. [PMID: 10838651]