Can levothyroxine be taken with other medications
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Can Levothyroxine Be Taken with Other Medications?
Levothyroxine, a synthetic form of the thyroid hormone thyroxine, is widely prescribed for the treatment of hypothyroidism. However, its absorption can be significantly affected by the concurrent intake of other medications and certain foods. This article explores the interactions between levothyroxine and other substances, providing insights into how to manage these interactions effectively.
Medications That Decrease Levothyroxine Absorption
Phosphate Binders and Nutritional Supplements
Several studies have shown that certain medications can interfere with the intestinal absorption of levothyroxine. For instance, sevelamer hydrochloride, a phosphate binder used to treat hyperphosphatemia, and chromium picolinate, a nutritional supplement, have both been found to significantly decrease the absorption of levothyroxine when taken simultaneously 12. Patients are advised to separate the ingestion of these medications from their thyroid hormone preparation by several hours to avoid this interaction .
Bile Acid Sequestrants and Antacids
Bile acid-binding resins such as colesevelam hydrochloride and lanthanum carbonate also inhibit levothyroxine absorption. This is believed to occur due to the formation of an insoluble complex between the thyroid hormone and these medications in the intestinal lumen . Additionally, other substances like iron salts, calcium carbonate, sucralfate, and aluminum-containing antacids have been reported to reduce levothyroxine absorption through similar mechanisms 24.
Proton Pump Inhibitors and Other Drugs
Proton pump inhibitors, which increase the pH of gastric acid, can impair the absorption of levothyroxine. Other drugs, including sex hormones and anticonvulsants, have also been identified as potential interferers . The proposed mechanisms for these interactions include direct complexing, alkalization, and alteration of serum thyroxine-binding globulin levels .
Food and Dietary Supplements
Impact of Food on Levothyroxine Absorption
The absorption of levothyroxine is known to be affected by the intake of certain foods and beverages. For example, coffee, soy products, fiber, and calcium or iron supplements can all decrease the absorption of levothyroxine . It is recommended that levothyroxine be taken on an empty stomach, at least 30 minutes before breakfast, to ensure optimal absorption 35.
Novel Formulations to Mitigate Food Effects
Recent studies have explored alternative formulations of levothyroxine, such as oral liquid solutions, which may mitigate the food effect by bypassing the gastric dissolution phase of absorption. These formulations have shown comparable bioavailability when taken 10 or 30 minutes before a high-fat, high-calorie breakfast, offering more flexibility for patients .
Managing Drug Interactions
Timing and Dose Adjustment
To manage the interactions between levothyroxine and other medications, it is crucial to maintain a proper time interval between the administration of levothyroxine and interfering substances. For instance, separating the intake of levothyroxine and calcium or iron supplements by at least four hours can help eliminate the interaction 49. Dose adjustments may also be necessary to ensure therapeutic efficacy .
Monitoring and Patient Education
Patients should be educated about the potential interactions and the importance of adhering to the recommended administration guidelines. Regular monitoring of serum thyroid-stimulating hormone (TSH) and free thyroxine (T4) levels is essential, especially when starting or discontinuing any interfering medications .
Conclusion
Levothyroxine's absorption can be significantly affected by various medications and foods. To ensure effective treatment of hypothyroidism, it is important to manage these interactions through proper timing of administration, dose adjustments, and patient education. Novel formulations of levothyroxine may offer additional flexibility, but further research is needed to confirm their benefits. By understanding and mitigating these interactions, patients and healthcare providers can optimize the therapeutic outcomes of levothyroxine therapy.
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