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Drug Interactions between Eltroxin and Uni-Lan

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

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Interactions between your drugs

Moderate

levothyroxine aluminum hydroxide

Applies to: Eltroxin (levothyroxine) and Uni-Lan (aluminum hydroxide / magnesium hydroxide / simethicone)

ADJUST DOSING INTERVAL: Concurrent administration of simethicone and/or antacid preparations may decrease the oral bioavailability of levothyroxine. Pharmacologic effects of levothyroxine may be reduced. The exact mechanism of interaction is unknown but may involve nonspecific adsorption of levothyroxine to polyvalent cations, resulting in an insoluble complex that is poorly absorbed from the gastrointestinal tract. Additionally, because gastric acidity is required for adequate levothyroxine absorption, agents that effect intragastric pH may reduce levothyroxine absorption. There have been case reports suggesting decreased efficacy of levothyroxine during coadministration of aluminum- and magnesium-containing antacids, as well as other products containing polyvalent cations such as calcium and iron. In one report, a man stabilized on levothyroxine 150 mcg/day developed significantly increased serum thyrotropin (thyroid-stimulating hormone, or TSH) levels while taking an aluminum and magnesium hydroxide antacid. The apparent interaction was also observed on two subsequent rechallenges. Other case reports have described increased dosage requirements of levothyroxine during antacid use. It is not known whether this interaction occurs with other thyroid hormone preparations.

MANAGEMENT: It is recommended to separate the times of administration of levothyroxine and simethicone and antacids or other antacid-containing preparations (e.g., didanosine buffered tablets or pediatric oral solution) 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. Sperber AD, Liel Y "Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide." Arch Intern Med 152 (1992): 183-4
  2. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  3. Campbell NR, Hasinoff BB, Stalts H, Rao B, Wong NC "Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism." Ann Intern Med 117 (1992): 1010-3
  4. Liel Y, Sperber AD, Shany S "Nonspecific intestinal adsorption of levothyroxine by aluminum hydroxide." Am J Med 97 (1994): 363-5
  5. Schneyer CR "Calcium carbonate and reduction of levothyroxine efficacy." JAMA 279 (1998): 750
  6. Singh N, Singh PN, Hershman JM "Effect of calcium carbonate on the absorption of levothyroxine." JAMA 283 (2000): 2822-5
  7. 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
  8. Neafsey PJ "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse 22 (2004): 338-9
  9. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  10. Canadian Pharmacists Association "e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink" (2006):
  11. Cerner Multum, Inc. "Australian Product Information." O 0
View all 11 references

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Moderate

levothyroxine magnesium hydroxide

Applies to: Eltroxin (levothyroxine) and Uni-Lan (aluminum hydroxide / magnesium hydroxide / simethicone)

ADJUST DOSING INTERVAL: Concurrent administration of simethicone and/or antacid preparations may decrease the oral bioavailability of levothyroxine. Pharmacologic effects of levothyroxine may be reduced. The exact mechanism of interaction is unknown but may involve nonspecific adsorption of levothyroxine to polyvalent cations, resulting in an insoluble complex that is poorly absorbed from the gastrointestinal tract. Additionally, because gastric acidity is required for adequate levothyroxine absorption, agents that effect intragastric pH may reduce levothyroxine absorption. There have been case reports suggesting decreased efficacy of levothyroxine during coadministration of aluminum- and magnesium-containing antacids, as well as other products containing polyvalent cations such as calcium and iron. In one report, a man stabilized on levothyroxine 150 mcg/day developed significantly increased serum thyrotropin (thyroid-stimulating hormone, or TSH) levels while taking an aluminum and magnesium hydroxide antacid. The apparent interaction was also observed on two subsequent rechallenges. Other case reports have described increased dosage requirements of levothyroxine during antacid use. It is not known whether this interaction occurs with other thyroid hormone preparations.

MANAGEMENT: It is recommended to separate the times of administration of levothyroxine and simethicone and antacids or other antacid-containing preparations (e.g., didanosine buffered tablets or pediatric oral solution) 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. Sperber AD, Liel Y "Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide." Arch Intern Med 152 (1992): 183-4
  2. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  3. Campbell NR, Hasinoff BB, Stalts H, Rao B, Wong NC "Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism." Ann Intern Med 117 (1992): 1010-3
  4. Liel Y, Sperber AD, Shany S "Nonspecific intestinal adsorption of levothyroxine by aluminum hydroxide." Am J Med 97 (1994): 363-5
  5. Schneyer CR "Calcium carbonate and reduction of levothyroxine efficacy." JAMA 279 (1998): 750
  6. Singh N, Singh PN, Hershman JM "Effect of calcium carbonate on the absorption of levothyroxine." JAMA 283 (2000): 2822-5
  7. 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
  8. Neafsey PJ "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse 22 (2004): 338-9
  9. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  10. Canadian Pharmacists Association "e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink" (2006):
  11. Cerner Multum, Inc. "Australian Product Information." O 0
View all 11 references

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Moderate

levothyroxine simethicone

Applies to: Eltroxin (levothyroxine) and Uni-Lan (aluminum hydroxide / magnesium hydroxide / simethicone)

ADJUST DOSING INTERVAL: Concurrent administration of simethicone and/or antacid preparations may decrease the oral bioavailability of levothyroxine. Pharmacologic effects of levothyroxine may be reduced. The exact mechanism of interaction is unknown but may involve nonspecific adsorption of levothyroxine to polyvalent cations, resulting in an insoluble complex that is poorly absorbed from the gastrointestinal tract. Additionally, because gastric acidity is required for adequate levothyroxine absorption, agents that effect intragastric pH may reduce levothyroxine absorption. There have been case reports suggesting decreased efficacy of levothyroxine during coadministration of aluminum- and magnesium-containing antacids, as well as other products containing polyvalent cations such as calcium and iron. In one report, a man stabilized on levothyroxine 150 mcg/day developed significantly increased serum thyrotropin (thyroid-stimulating hormone, or TSH) levels while taking an aluminum and magnesium hydroxide antacid. The apparent interaction was also observed on two subsequent rechallenges. Other case reports have described increased dosage requirements of levothyroxine during antacid use. It is not known whether this interaction occurs with other thyroid hormone preparations.

MANAGEMENT: It is recommended to separate the times of administration of levothyroxine and simethicone and antacids or other antacid-containing preparations (e.g., didanosine buffered tablets or pediatric oral solution) 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. Sperber AD, Liel Y "Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide." Arch Intern Med 152 (1992): 183-4
  2. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  3. Campbell NR, Hasinoff BB, Stalts H, Rao B, Wong NC "Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism." Ann Intern Med 117 (1992): 1010-3
  4. Liel Y, Sperber AD, Shany S "Nonspecific intestinal adsorption of levothyroxine by aluminum hydroxide." Am J Med 97 (1994): 363-5
  5. Schneyer CR "Calcium carbonate and reduction of levothyroxine efficacy." JAMA 279 (1998): 750
  6. Singh N, Singh PN, Hershman JM "Effect of calcium carbonate on the absorption of levothyroxine." JAMA 283 (2000): 2822-5
  7. 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
  8. Neafsey PJ "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse 22 (2004): 338-9
  9. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  10. Canadian Pharmacists Association "e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink" (2006):
  11. Cerner Multum, Inc. "Australian Product Information." O 0
View all 11 references

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Drug and food interactions

Major

aluminum hydroxide food

Applies to: Uni-Lan (aluminum hydroxide / magnesium hydroxide / simethicone)

GENERALLY AVOID: The concomitant administration of aluminum-containing products (e.g., antacids and phosphate binders) and citrates may significantly increase serum aluminum concentrations, resulting in toxicity. Citrates or citric acid are contained in numerous soft drinks, citrus fruits, juices, and effervescent and dispersible drug formulations. Citrates enhance the gastrointestinal absorption of aluminum by an unknown mechanism, which may involve the formation of a soluble aluminum-citrate complex. Various studies have reported that citrate increases aluminum absorption by 4.6- to 50-fold in healthy subjects. Patients with renal insufficiency are particularly at risk of developing hyperaluminemia and encephalopathy. Fatalities have been reported. Patients with renal failure or on hemodialysis may also be at risk from soft drinks and effervescent and dispersible drug formulations that contain citrates or citric acid. It is unknown what effect citrus fruits or juices would have on aluminum absorption in healthy patients.

MANAGEMENT: The concomitant use of aluminum- and citrate-containing products and foods should be avoided by renally impaired patients. Hemodialysis patients should especially be cautioned about effervescent and dispersible over-the-counter remedies and soft drinks. Some experts also recommend that healthy patients should separate doses of aluminum-containing antacids and citrates by 2 to 3 hours.

ADJUST DOSING INTERVAL: The administration of aluminum-containing antacids with enteral nutrition may result in precipitation, formation of bezoars, and obstruction of feeding tubes. The proposed mechanism is the formation of an insoluble complex between the aluminum and the protein in the enteral feeding. Several cases of esophageal plugs and nasogastric tube obstructions have been reported in patients receiving high-protein liquids and an aluminum hydroxide-magnesium hydroxide antacid or an aluminum hydroxide antacid.

MANAGEMENT: Some experts recommend that antacids should not be mixed with or given after high protein formulations, that the antacid dose should be separated from the feeding by as much as possible, and that the tube should be thoroughly flushed before administration.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. 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

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Moderate

levothyroxine food

Applies to: Eltroxin (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

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Moderate

levothyroxine food

Applies to: Eltroxin (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
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.

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