Drug General Information (ID: DDIG04VULQ)
Drug Name			Colestipol		Drug Info		Levothyroxine		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Bile Acid Sequestrants				Antithyroid Agents
Structure

Mechanism of Colestipol-Levothyroxine Interaction (Severity Level: Moderate)
Altered Fat-soluble drugs absorption Click to Show/Hide Mechanism Graph
Drug Name		Colestipol				Levothyroxine
Mechanism		Decrease fat-soluble agent absorption				Fat-soluble agent
Key Mechanism Factor 1
		Factor Name		Pharmacokinetic
		Factor Description		Alters the absorption of the drug, leading to changes in the plasma concentration of the drug and affecting the pharmacological effects.
Mechanism Description		Decreased absorption of Levothyroxine caused by Colestipol

Recommended Action
Management		Thyroid hormone preparations and bile acid sequestrants should be administered at least 4 hours apart. Close clinical and laboratory monitoring of thyroid function is recommended during coadministration, since adjusting the dosing interval may not completely prevent the interaction.

References
1	Cashin-Hemphill L, Spencer CA, Nicoloff JT, Blankenhorn DH, Nessim SA, Chin HP, Lee NA "Alterations in serum thyroid hormonal indices with colestipol-niacin therapy." Ann Intern Med 107 (1987): 324-9. [PMID: 3113309]
2	Harmon SM, Seifert CF "Levothyroxine-cholestyramine interaction reemphasized." Ann Intern Med 115 (1991): 658-9. [PMID: 1892339]
3	Northcutt RC, Stiel JN, Hollifield JW, Stant EG "The influence of cholestyramine on thyroxine absorption." JAMA 208 (1969): 1857-61. [PMID: 5818830]
4	Product Information. Questran (cholestyramine). Par Pharmaceutical Inc, Chestnut Ridge, NY.
5	Product Information. Synthroid (levothyroxine). Abbott Pharmaceutical, Abbott Park, IL.