Drug General Information (ID: DDI30VT8UD)
Drug Name			Levothyroxine		Drug Info		Didanosine		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antithyroid Agents				Anti-Hiv Agents
Structure

Mechanism of Levothyroxine-Didanosine Interaction (Severity Level: Moderate)
Complex formation Click to Show/Hide Mechanism Graph
Drug Name		Levothyroxine				Didanosine
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 Didanosine due to formation of complexes caused by Levothyroxine

Recommended Action
Management		It is recommended to separate the times of administration of levothyroxine and simethicone and antacids or other antacid-containing preparations (e.g., didanosine buffered tablets or pediatric oral solution) 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	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]
2	Canadian Pharmacists Association.
3	Cerner Multum, Inc. "Australian Product Information.".
4	Cerner Multum, Inc. "UK Summary of Product Characteristics.".
5	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]
6	Liel Y, Sperber AD, Shany S "Nonspecific intestinal adsorption of levothyroxine by aluminum hydroxide." Am J Med 97 (1994): 363-5. [PMID: 7942938]
7	Neafsey PJ "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse 22 (2004): 338-9. [PMID: 15131426]
8	Product Information. Synthroid (levothyroxine). Abbott Pharmaceutical, Abbott Park, IL.
9	Schneyer CR "Calcium carbonate and reduction of levothyroxine efficacy." JAMA 279 (1998): 750. [PMID: 9508149]
10	Singh N, Singh PN, Hershman JM "Effect of calcium carbonate on the absorption of levothyroxine." JAMA 283 (2000): 2822-5. [PMID: 10838651]
11	Sperber AD, Liel Y "Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide." Arch Intern Med 152 (1992): 183-4. [PMID: 1728914]