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6 Interactions found for:

Vitamin D3 and levothyroxine
Interactions Summary
  • 0 Major
  • 2 Moderate
  • 4 Minor
  • Vitamin D3
  • levothyroxine

Drug Interactions

No drug interactions were found for selected drugs: Vitamin D3, levothyroxine.

This does not necessarily mean no interactions exist. Always consult your healthcare provider.

Drug and Food Interactions

Moderate
Levothyroxine + Food

The following applies to the ingredients: Levothyroxine

ADJUST DOSING INTERVAL: Consumption of certain foods as well as the timing of meals relative to dosing may affect the oral absorption of T4 thyroid hormone (i.e., levothyroxine). T4 oral absorption is increased by fasting and decreased by foods such as soybean flour (e.g., infant formula), cotton seed meal, walnuts, dietary fiber, calcium, and calcium fortified juices. Grapefruit or grapefruit products may delay the absorption of T4 thyroid hormone and reduce its bioavailability. The mechanism of this interaction is not fully understood.

MANAGEMENT: Some manufacturers recommend administering oral T4 as a single daily dose, on an empty stomach, one-half to one hour before breakfast. In general, oral preparations containing T4 thyroid hormone should be administered on a consistent schedule with regard to time of day and relation to meals to avoid large fluctuations in serum levels. Foods that may affect T4 absorption should be avoided within several hours of dosing if possible. Consult local guidelines for the administration of T4 in patients receiving enteral feeding.

References

  1. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  2. "Product Information. Armour Thyroid (thyroid desiccated)." Forest Pharmaceuticals (2022):
  3. Wohlt PD, Zheng L, Gunderson S, Balzar SA, Johnson BD, Fish JT "Recommendations for the use of medications with continuous enteral nutrition." Am J Health Syst Pharm 66 (2009): 1438-67

The following applies to the ingredients: Levothyroxine

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

Moderate
Vitamin D3 + Food

The following applies to the ingredients: Cholecalciferol (found in Vitamin D3)

MONITOR: Additive effects and possible toxicity (e.g., hypercalcemia, hypercalciuria, and/or hyperphosphatemia) may occur when patients using vitamin D and/or vitamin D analogs ingest a diet high in vitamin D, calcium, and/or phosphorus. The biologically active forms of vitamin D stimulate intestinal absorption of calcium and phosphorus. This may be helpful in patients with hypocalcemia and/or hypophosphatemia. However, sudden increases in calcium or phosphorus consumption due to dietary changes could precipitate hypercalcemia and/or hyperphosphatemia. Patients with certain disease states, such as impaired renal function, may be more susceptible to toxic side effects like ectopic calcification. On the other hand, if dietary calcium is inadequate for the body's needs, the active form of vitamin D will stimulate osteoclasts to pull calcium from the bones. This may be detrimental in a patient with reduced bone density.

MANAGEMENT: Given the narrow therapeutic index of vitamin D and vitamin D analogs, the amounts of calcium, phosphorus, and vitamin D present in the patient's diet may need to be taken into consideration. Specific dietary guidance should be discussed with the patient and regular lab work should be monitored as indicated. Calcium, phosphorus, and vitamin D levels should be kept within the desired ranges, which may differ depending on the patient's condition. Patients should also be counseled on the signs and symptoms of hypervitaminosis D, hypercalcemia, and/or hyperphosphatemia.

References

  1. "Product Information. Drisdol (ergocalciferol)." Validus Pharmaceuticals LLC (2023):
  2. "Product Information. Fultium-D3 (colecalciferol)." Internis Pharmaceuticals Ltd (2024):
  3. "Product Information. Ostelin Specialist Range Vitamin D (colecalciferol)." Sanofi-Aventis Healthcare Pty Ltd T/A Sanofi Consumer Healthcare (2024):
  4. "Product Information. Rocaltrol (calcitriol)." Atnahs Pharma UK Ltd (2021):
  5. "Product Information. Calcitriol (calcitriol)." Strides Pharma Inc. (2019):
  6. "Product Information. Calcitriol (GenRx) (calcitriol)." Apotex Pty Ltd (2024):
  7. "Product Information. Ergocalciferol (ergocalciferol)." RPH Pharmaceuticals AB (2022):
  8. "Product Information. Sandoz D (cholecalciferol)." Sandoz Canada Incorporated (2020):
  9. Fischer V, Haffner-Luntzer M, Prystaz K, et al. "Calcium and vitamin-D deficiency marginally impairs fracture healing but aggravates posttraumatic bone loss in osteoporotic mice. https://www.nature.com/articles/s41598-017-07511-2" (2024):
  10. National Institutes of Health Office of Dietary Supplements "Vitamin D https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/#h37" (2024):

Drug and Pregnancy Interactions

The following applies to the ingredients: Levothyroxine

Use is considered acceptable

AU TGA pregnancy category: A
US FDA pregnancy category: Not Assigned

Risk Summary: No increased rates of major birth defects or miscarriages have been reported with use during pregnancy; untreated hypothyroidism during pregnancy is associated with risks to the mother and fetus

Comments:
-Thyroid replacement therapy should not be discontinued during pregnancy; hypothyroidism diagnosed during pregnancy should be promptly treated.
-Monitor TSH levels and adjust doses as needed.

Animal studies have not been conducted. There is a long history of using this drug in pregnant women and this experience has not shown increased rates of fetal malformations, miscarriages or other adverse maternal or fetal outcomes. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal neurocognitive development. Pregnant women taking this drug should have their TSH measured during each trimester and dose adjusted as appropriate. Patients will generally return to their pre-pregnancy dose after delivery. There are no controlled data in human pregnancy.

AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

References

  1. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
  4. Cerner Multum, Inc. "Australian Product Information." O 0

The following applies to the ingredients: Cholecalciferol (found in Vitamin D3)

Use is not recommended unless there is a deficiency.

AU TGA pregnancy category: Exempt
US FDA pregnancy category: Not assigned

Comments:
-Vitamin D supplementation should begin a few months prior to pregnancy.

Animal studies at high doses have shown teratogenicity. There are no controlled data in human pregnancy. Because vitamin D raises calcium levels, it is suspect in the pathogenesis of supravalvular aortic stenosis syndrome, which is often associated with idiopathic hypercalcemia of infancy, but excessive vitamin D intake or retention has not been found consistently in these mothers. A study of 15 patients with maternal hypoparathyroidism, treated with high dose vitamin D during pregnancy (average 107,000 international units per day) to maintain normal calcium levels, produced all normal children. Vitamin D deficiency is associated with reduced fetal growth, neonatal hypocalcemia (with and without convulsions), rickets, and defective tooth enamel.

AU TGA pregnancy category Exempt: Medicines exempted from pregnancy classification are not absolutely safe for use in pregnancy in all circumstances. Some exempted medicines, for example the complementary medicine, St John's Wort, may interact with other medicines and induce unexpected adverse effects in the mother and/or fetus.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decision and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D and X are being phased out.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. Cerner Multum, Inc. "Australian Product Information." O 0
  3. TGA. Therapeutic Goods Administration. Australian Drug Evaluation Committee "Prescribing medicines in pregnancy: an Australian categorisation of risk of drug use in pregnancy. http://www.tga.gov.au/docs/html/medpreg.htm" (2010):
  4. Briggs GG, Freeman RK. "Drugs in Pregnancy and Lactation." Philadelphia, PA: Wolters Kluwer Health (2015):

Drug and Breastfeeding Interactions

The following applies to the ingredients: Levothyroxine

Use is considered acceptable

Excreted into human milk: Yes

Comments:
-Levothyroxine (T4) is a normal component of human milk; limited data on exogenous replacement doses during breastfeeding have not shown an adverse effect in nursing infants.
-Levothyroxine dose requirements may be increased in the postpartum period compared to prepregnancy requirements in patients with Hashimoto's thyroiditis.
-The presence of thyroid hormone in breast milk does not appear to interfere with neonatal thyroid screening.

References

  1. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  2. Jansson L, Ivarsson S, Larsson I, Ekman R "Tri-iodothyronine and thyroxine in human milk." Acta Paediatr Scand 72 (1983): 703-5
  3. Moller B, Bjorkhem I, Falk O, Lantto O, Lafsson A "Identification of thyroxine in human breast milk by gas chromatography-mass spectrometry." J Clin Endocrinol Metab 56 (1983): 30-4
  4. Mizuta H, Amino N, Ichihara K, et al. "Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies." Pediatr Res 17 (1983): 468-71
  5. Hahn HB, Spiekerman AM, Otto R, Hossalla DE "Thyroid function tests in neonates fed human milk." Am J Dis Child 137 (1983): 220-2
  6. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  7. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
  8. Cerner Multum, Inc. "Australian Product Information." O 0
  9. United States National Library of Medicine "Toxnet. Toxicology Data Network. http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT" (2013):

The following applies to the ingredients: Cholecalciferol (found in Vitamin D3)

Use is not recommended unless the clinical condition of the woman requires treatment.

Excreted into human milk: Yes

Comments:
-Make allowance for any maternal dose if prescribing this product to a breast fed infant.
-Consider monitoring the infant's serum calcium if the mother is receiving pharmacologic doses of vitamin D.
-Vitamin D supplementation is recommended in exclusively breast fed infants.

The required dose of vitamin D during lactation has not been adequately studied; doses similar to those for pregnant women have been suggested.

Chronic ingestion of large doses of vitamin D by the mother may lead to hypercalcemia in the breastfed infant.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. Cerner Multum, Inc. "Australian Product Information." O 0
  3. Briggs GG, Freeman RK. "Drugs in Pregnancy and Lactation." Philadelphia, PA: Wolters Kluwer Health (2015):
  4. IOM (Institute of Medicine). "Dietary Reference Intakes for Calcium and Vitamin D." Washington, DC: The National Academies Press (2011):

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.

Switch to: Consumer Interactions

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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