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Drug Interactions between fluoxymesterone and liothyronine

This report displays the potential drug interactions for the following 2 drugs:

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Moderate

fluoxymesterone liothyronine

Applies to: fluoxymesterone and liothyronine

MONITOR: Concomitant use of androgens and/or anabolic steroids or corticosteroids with thyroid hormone replacement therapy, may cause a transient decrease in thyroid hormone replacement requirements. The proposed mechanism is a decrease in T4 binding globulin resulting in an initial transient increase in free T4. However, continued administration results in a decrease in serum T4 and normal free T4 and TSH concentrations. In addition, the clearance of corticosteroids may be increased in hyperthyroid patients, and decreased in hypothyroid patients, changes in thyroid hormone replacement dosage may affect corticosteroid dosage. Glucocorticoids may also inhibit the peripheral conversion of T4 to its active form T3. In addition, initiation of thyroid hormone replacement prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency.

MANAGEMENT: Clinical and laboratory monitoring of thyroid function is recommended for patients receiving thyroid hormone replacement therapy and androgens and/or anabolic steroids, or corticosteroids. Thyroid hormone dosage adjustments may be needed. Patients should be advised to contact their physician if clinical manifestations of hyperthyroidism occur, such as appetite changes, unexplained weight loss, insomnia, and fatigue. In addition, when the dosage of the thyroid medication is changed, the corticosteroid dosage may need to be adjusted. Patients with adrenal insufficiency should be treated with replacement glucocorticoids prior to initiating thyroid hormone replacement.

References (8)
  1. Arafah BM (1994) "Decreased levothyroxine requirement in women with hypothyroidism during androgen therapy for breast cancer." Ann Intern Med, 121, p. 247-51
  2. (2024) "Product Information. Synthroid (levothyroxine)." AbbVie US LLC
  3. (2024) "Product Information. Levothyroxine Sodium (levothyroxine)." Lannett Company Inc
  4. (2023) "Product Information. Levothyroxine Sodium (levothyroxine)." Zentiva Pharma UK Ltd
  5. (2023) "Product Information. Levothyroxine (Sandoz) (levothyroxine sodium)." Sandoz Pty Ltd
  6. (2024) "Product Information. Liothyronine Sodium (liothyronine)." AvKare Inc
  7. (2024) "Product Information. Eltroxin (levothyroxine)." Shire US Inc
  8. (2024) "Product Information. Armour Thyroid (thyroid desiccated)." A-S Medication Solutions

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Drug and food interactions

Moderate

liothyronine food

Applies to: liothyronine

ADJUST DOSING INTERVAL: Concurrent administration of calcium-containing products may decrease the oral bioavailability of levothyroxine by one-third in some patients. Pharmacologic effects of levothyroxine may be reduced. The exact mechanism of interaction is unknown but may involve nonspecific adsorption of levothyroxine to calcium at acidic pH levels, resulting in an insoluble complex that is poorly absorbed from the gastrointestinal tract. In one study, 20 patients with hypothyroidism who were taking a stable long-term regimen of levothyroxine demonstrated modest but significant decreases in mean free and total thyroxine (T4) levels as well as a corresponding increase in mean thyrotropin (thyroid-stimulating hormone, or TSH) level following the addition of calcium carbonate (1200 mg/day of elemental calcium) for 3 months. Four patients had serum TSH levels that were higher than the normal range. Both T4 and TSH levels returned to near-baseline 2 months after discontinuation of calcium, which further supported the likelihood of an interaction. In addition, there have been case reports suggesting decreased efficacy of levothyroxine during calcium coadministration. It is not known whether this interaction occurs with other thyroid hormone preparations.

MANAGEMENT: Some experts recommend separating the times of administration of levothyroxine and calcium-containing preparations 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 (4)
  1. Schneyer CR (1998) "Calcium carbonate and reduction of levothyroxine efficacy." JAMA, 279, p. 750
  2. Singh N, Singh PN, Hershman JM (2000) "Effect of calcium carbonate on the absorption of levothyroxine." JAMA, 283, p. 2822-5
  3. Csako G, McGriff NJ, Rotman-Pikielny P, Sarlis NJ, Pucino F (2001) "Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders." Ann Pharmacother, 35, p. 1578-83
  4. Neafsey PJ (2004) "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse, 22, p. 338-9

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Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

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