Drug General Information (ID: DDIA8PCXL0)
Drug Name			Liothyronine		Drug Info		Conjugated estrogens (topical)		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Hormone Replacement Agents				Estrogens
Structure

Mechanism of Liothyronine-Conjugated estrogens (topical) Interaction (Severity Level: Moderate)
Increase globulin concentration Click to Show/Hide Mechanism Graph
Drug Name		Liothyronine				Conjugated estrogens (topical)
Mechanism		Thyroid hormone				Increase serum thyroid-binding globulin concentration
Key Mechanism Factor 1
		Factor Name		Pharmacokinetics
		Factor Description		Alters the distribution of the drug, leading to changes in the plasma concentration of the drug and affecting the pharmacological effects.
Mechanism Description		Decreased plasma concentration of Liothyronine caused by Conjugated estrogens (topical) mediated increased concentration of serum thyroid-binding globulin

Recommended Action
Management		In patients treated with thyroxine, serum thyrotropin should be measured approximately 12 weeks after estrogen therapy is initiated, changed or discontinued, and the thyroxine dosage adjusted accordingly. Patients should be advised to contact their physician if clinical manifestations of hypothyroidism occur, such as fatigue, cold intolerance, constipation, unexplained weight gain, depression, joint or muscle pain, thinning hair or hair loss, dry skin, hoarseness, and abnormal menstrual periods.

References
1	Arafah BM "Increased need for thyroxine in women with hypothyroidism during estrogen therapy." N Engl J Med 344 (2001): 1743-9. [PMID: 11396440]
2	Product Information. Synthroid (levothyroxine). Abbott Pharmaceutical, Abbott Park, IL.
3	Utiger RD "Estrogen, thyroxine binding in serum, and thyroxine therapy." N Engl J Med 344 (2001): 1784-5. [PMID: 11396448]