Details of Drug Interaction

Details of Drug-Drug Interaction

 Drug General Information (ID: DDIURPYQNI)
  Drug Name Conjugated estrogens Drug Info Levothyroxine Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Estrogens Antithyroid Agents
  Structure

 Mechanism of Conjugated estrogens-Levothyroxine Interaction (Severity Level: Moderate)
     Increase globulin concentration Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Conjugated estrogens Levothyroxine
      Mechanism Increase serum thyroid-binding globulin concentration Thyroid hormone
      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 Levothyroxine caused by Conjugated estrogens 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 Chetkowski RJ, Meldrum DR, Steingold KA, et al. "Biologic effects of transdermal estradiol." N Engl J Med 314 (1986): 1615-20. [PMID: 3012339]
3 Irving S, Vadiveloo T, Leese GP "Drugs that interact with levothyroxine an observational study from the Thyroid Epidemiology, Audit and Research Study (TEARS)." Clin Endocrinol (Oxf) (2014):. [PMID: 25040647]
4 Product Information. Nextstellis (drospirenone-estetrol). Mayne Pharma, Greenville, NC.
5 Product Information. Synthroid (levothyroxine). Abbott Pharmaceutical, Abbott Park, IL.
6 Utiger RD "Estrogen, thyroxine binding in serum, and thyroxine therapy." N Engl J Med 344 (2001): 1784-5. [PMID: 11396448]