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Drug Interactions between pseudoephedrine / terfenadine and Thyroid Porcine

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

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Interactions between your drugs

Moderate

thyroid desiccated pseudoephedrine

Applies to: Thyroid Porcine (thyroid desiccated) and pseudoephedrine / terfenadine

MONITOR: The concomitant use of thyroid hormones, especially large doses, with sympathomimetic drugs may potentiate sympathomimetic effects and increase the risk of cardiac insufficiency in patients who have coronary artery disease.

MANAGEMENT: Monitoring for increased sympathomimetic effects and cardiac function may be advisable.

References

  1. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  2. "Product Information. Armour Thyroid (thyroid desiccated)." Forest Pharmaceuticals (2022):
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  4. Agencia Española de Medicamentos y Productos Sanitarios Healthcare "Centro de información online de medicamentos de la AEMPS - CIMA. https://cima.aemps.es/cima/publico/home.html" (2008):
View all 4 references

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Drug and food interactions

Major

terfenadine food

Applies to: pseudoephedrine / terfenadine

CONTRAINDICATED: The consumption of grapefruit juice has been associated with significantly increased plasma concentrations of terfenadine. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. Terfenadine in high serum levels has been associated with prolongation of the QT interval and development of torsade de pointes, a potentially fatal ventricular arrhythmia.

MANAGEMENT: Due to the risk of cardiotoxicity, patients receiving the drug should be advised to avoid consumption of grapefruit products. Loratadine, cetirizine, and fexofenadine may be safer alternatives in patients who may have trouble adhering to the dietary restriction.

References

  1. Honig PK, Woosley RL, Zamani K, Conner DP, Cantilena LR Jr "Changes in the pharmacokinetics and electrocardiographic pharmacodynamics of terfenadine with concomitant administration of erythromycin." Clin Pharmacol Ther 52 (1992): 231-8
  2. Zimmermann M, Duruz H, Guinand O, et al. "Torsades de Pointes after treatment with terfenadine and ketoconazole." Eur Heart J 13 (1992): 1002-3
  3. Mathews DR, McNutt B, Okerholm R, et al. "Torsades de pointes occurring in association with terfenadine use." JAMA 266 (1991): 2375-6
  4. Monahan BP, Ferguson CL, Killeavy ES, et al. "Torsades de pointes occurring in association with terfenadine use." JAMA 264 (1990): 2788-90
  5. Honig PK, Wortham DC, Zamani K, et al. "Terfenadine-ketoconazole interaction: pharmacokinetic and electrocardiographic consequences." JAMA 269 (1993): 1513-8
  6. Pohjola-Sintonen S, Viitasalo M, Toivonene L, Neuvonen P "Torsades de pointes after terfenadine-itraconazole interaction." BMJ 306 (1993): 186
  7. Cortese LM, Bjornson DC "Potential interaction between terfenadine and macrolide antibiotics." Clin Pharm 11 (1992): 675
  8. Paris DG, Parente TF, Bruschetta HR, Guzman E, Niarchos AP "Torsades-de-pointes induced by erythromycin and terfenadine." Am J Emerg Med 12 (1994): 636-8
  9. Zechnich AD, Haxby DG "Drug interactions associated with terfenadine and related nonsedating antihistamines." West J Med 164 (1996): 68-9
  10. Honig PK, Wortham DC, Lazarev A, Cantilena LR "Grapefruit juice alters the systemic bioavailability and cardiac repolarization of terfenadine in poor metabolizers of terfenadine." J Clin Pharmacol 36 (1996): 345-51
  11. Woosley RL "Cardiac actions of antihistamines." Annu Rev Pharmacol Toxicol 36 (1996): 233-52
  12. Benton RE, Honig PK, Zamani K, Cantilena LR, Woosley RL "Grapefruit juice alters terfenadine pharmacokinetics resulting in prolongation of repolarization on the electrocardiogram." Clin Pharmacol Ther 59 (1996): 383-8
  13. Hsieh MH, Chen SA, Chiang CE, et al. "Drug-induced torsades de pointes in one patient with congenital long QT syndrome." Int J Cardiol 54 (1996): 85-8
  14. Clifford CP, Adams DA, Murray S, Taylor GW, Wilkins MR, Boobis AR, Davies DS "Pharmacokinetic and cardiac effects of terfenadine after inhibition of its metabolism by grapefruit juice." Br J Clin Pharmacol 42 (1996): p662
  15. Rau SE, Bend JR, Arnold JMO, Tran LT, Spence JD, Bailey DG "Grapefruit juice terfenadine single-dose interaction: Magnitude, mechanism, and relevance." Clin Pharmacol Ther 61 (1997): 401-9
  16. Bailey DG, Malcolm J, Arnold O, Spence JD "Grapefruit juice-drug interactions." Br J Clin Pharmacol 46 (1998): 101-10
  17. Bailey DG, Dresser GR, Kreeft JH, Munoz C, Freeman DJ, Bend JR "Grapefruit-felodipine interaction: Effect of unprocessed fruit and probable active ingredients." Clin Pharmacol Ther 68 (2000): 468-77
View all 17 references

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Moderate

thyroid desiccated food

Applies to: Thyroid Porcine (thyroid desiccated)

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

thyroid desiccated food

Applies to: Thyroid Porcine (thyroid desiccated)

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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Moderate

pseudoephedrine food

Applies to: pseudoephedrine / terfenadine

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.

References

  1. Rosenblatt JE, Lake CR, van Kammen DP, Ziegler MG, Bunney WE Jr "Interactions of amphetamine, pimozide, and lithium on plasma norepineophrine and dopamine-beta-hydroxylase in schizophrenic patients." Psychiatry Res 1 (1979): 45-52
  2. Cavanaugh JH, Griffith JD, Oates JA "Effect of amphetamine on the pressor response to tyramine: formation of p-hydroxynorephedrine from amphetamine in man." Clin Pharmacol Ther 11 (1970): 656
  3. "Product Information. Adderall (amphetamine-dextroamphetamine)." Shire Richwood Pharmaceutical Company Inc PROD (2001):
  4. "Product Information. Tenuate (diethylpropion)." Aventis Pharmaceuticals PROD (2001):
  5. "Product Information. Sanorex (mazindol)." Novartis Pharmaceuticals PROD (2001):
  6. "Product Information. Focalin (dexmethylphenidate)." Mikart Inc (2001):
  7. "Product Information. Strattera (atomoxetine)." Lilly, Eli and Company (2002):
View all 7 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

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