Drug General Information (ID: DDI1WA5JXB)
Drug Name			Norethisterone		Drug Info		Colesevelam		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Contraceptive Agents				Bile Acid Sequestrants
Structure

Mechanism of Norethisterone-Colesevelam Interaction (Severity Level: Moderate)
Complex formation Click to Show/Hide Mechanism Graph
Drug Name		Norethisterone				Colesevelam
Mechanism		Binds to anion exchange resin/polymer				Anion exchange resin/polymer
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 Colesevelam due to formation of complexes caused by Norethisterone

Recommended Action
Management		Oral contraceptives containing ethinyl estradiol and norethindrone should be administered at least 4 hours before the colesevelam dose. The same precaution may be applicable to other contraceptive hormones, although data are lacking.

References
1	Bailey DG, Arnold JMO, Spence JD "Grapefruit juice and drugs - how significant is the interaction." Clin Pharmacokinet 26 (1994): 91-8. [PMID: 8162660]
2	Gunston GD, Mehta U "Potentially serious drug interactions with grapefruit juice." S Afr Med J 90 (2000): 41. [PMID: 10721388]
3	Product Information. Welchol (colesevelam) Daiichi Sankyo, Inc., Parsippany, NJ.