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Drug Interactions between liothyronine and Valertest No 1

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

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Interactions between your drugs

Moderate

estradiol liothyronine

Applies to: Valertest No 1 (estradiol / testosterone) and liothyronine

MONITOR: Estrogens may increase serum thyrotropin concentration, which could be harmful in patients with thyroid cancer receiving thyroxine for thyrotropin suppression or increase dosage requirements in patients with hypothyroidism receiving thyroxine for replacement therapy. Estrogens are known to increase serum thyroid-binding globulin concentration. Consequently, there may be a reduction in unbound, or free, thyroxine available for hormone activity, which, in turn, leads to an increase in serum thyrotropin concentration. Normally, thyroxine secretion can increase to compensate for this effect, but patients with hypothyroidism may lack the mechanism to adapt.

MANAGEMENT: Clinical and laboratory monitoring of thyroid function is recommended for patients receiving thyroid hormone replacement therapy and estrogens. Thyroid hormone dosage adjustments may be needed. 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. (2002) "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical
  2. Chetkowski RJ, Meldrum DR, Steingold KA, et al. (1986) "Biologic effects of transdermal estradiol." N Engl J Med, 314, p. 1615-20
  3. Arafah BM (2001) "Increased need for thyroxine in women with hypothyroidism during estrogen therapy." N Engl J Med, 344, p. 1743-9
  4. Utiger RD (2001) "Estrogen, thyroxine binding in serum, and thyroxine therapy." N Engl J Med, 344, p. 1784-5
  5. Irving S, Vadiveloo T, Leese GP (2014) "Drugs that interact with levothyroxine; an observational study from the Thyroid Epidemiology, Audit and Research Study (TEARS)." Clin Endocrinol (Oxf)
  6. (2021) "Product Information. Nextstellis (drospirenone-estetrol)." Mayne Pharma
  7. (2024) "Product Information. Levothyroxine Sodium (levothyroxine)." Lannett Company Inc
  8. (2023) "Product Information. Levothyroxine Sodium (levothyroxine)." Zentiva Pharma UK Ltd
  9. (2024) "Product Information. Liothyronine Sodium (liothyronine)." AvKare Inc
  10. (2024) "Product Information. Estradiol (estradiol)." Alexso Inc
View all 10 references

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Moderate

testosterone liothyronine

Applies to: Valertest No 1 (estradiol / testosterone) and liothyronine

MONITOR: Androgens may induce reversible clinical hyperthyroidism in patients receiving thyroid hormone replacement therapy. The proposed mechanism is androgen-induced decrease in T4 binding globulin resulting in decreased serum T4, increased T3 uptake resin and free T4, and decreased TSH levels.

MANAGEMENT: Clinical and laboratory monitoring of thyroid function may be necessary, as may a 25% to 50% reduction in thyroid hormone dosage.

References

  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
View all 8 references

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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

  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
View all 4 references

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Minor

estradiol food

Applies to: Valertest No 1 (estradiol / testosterone)

Coadministration with grapefruit juice may increase the bioavailability of oral estrogens. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In a small, randomized, crossover study, the administration of ethinyl estradiol with grapefruit juice (compared to herbal tea) increased peak plasma drug concentration (Cmax) by 37% and area under the concentration-time curve (AUC) by 28%. Based on these findings, grapefruit juice is unlikely to affect the overall safety profile of ethinyl estradiol. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability. Also, the effect on other estrogens has not been studied.

References

  1. Weber A, Jager R, Borner A, et al. (1996) "Can grapefruit juice influence ethinyl estradiol bioavailability?" Contraception, 53, p. 41-7
  2. Schubert W, Eriksson U, Edgar B, Cullberg G, Hedner T (1995) "Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17B-estradiol." Eur J Drug Metab Pharmacokinet, 20, p. 219-24

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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.

See also

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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.

Further information

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