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Drug Interactions between orlistat and Triostat

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

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Interactions between your drugs

Moderate

liothyronine orlistat

Applies to: Triostat (liothyronine) and orlistat

ADJUST DOSING INTERVAL: Orlistat may interfere with the gastrointestinal absorption of levothyroxine and other thyroid hormones. The exact mechanism of interaction is unknown. In one case report, symptomatic hypothyroidism occurred within two weeks following the initiation of orlistat in a patient with thyroid cancer who had been receiving levothyroxine for 18 months to suppress thyroid-stimulating hormone production after a total thyroidectomy and radioiodine ablation. The patient complained of tiredness, lethargy and cold intolerance, and thyroid function tests revealed profound hypothyroidism. Symptoms improved two weeks following the discontinuation of orlistat and an increase of levothyroxine dosage from 250 to 300 mcg/day. Laboratory values returned to normal another two weeks later.

MANAGEMENT: Orlistat and oral thyroid hormone preparations should be administered at least 4 hours apart. Close clinical and laboratory monitoring of thyroid function is recommended. Patients should be advised to contact their physician if they experience symptoms of hypothyroidism such as fatigue, muscle weakness or pain, joint stiffness, depression, constipation, hoarseness, weight gain, hair loss, brittle nails, pale or dry skin, cold intolerance, memory problems, confusion, or menstrual irregularities.

References

  1. (2002) "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical
  2. (2001) "Product Information. Xenical (orlistat)." Roche Laboratories
  3. Filippatos TD, Derdemezis CS, Gazi IF, Nakou ES, Mikhailidis DP, Elisaf MS (2008) "Orlistat-associated adverse effects and drug interactions: a critical review." Drug Saf, 31, p. 53-65
  4. Madhava K, Hartley A (2005) "Hypothyroidism in thyroid carcinama follow-up: orlistat may inhibit the absorption of thyroxine." Clin Oncol, 17, p. 492
View all 4 references

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Drug and food interactions

Moderate

liothyronine food

Applies to: Triostat (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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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.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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