Tirosint vs synthroid

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Tirosint vs Synthroid: A Comparative Analysis

Pharmacokinetic Equivalence of Tirosint and Synthroid

Pharmacokinetic Equivalence
A study comparing the pharmacokinetic profiles of Tirosint, a levothyroxine sodium soft capsule, and Synthroid, a tablet formulation, found that both products are bioequivalent. This means that the rate and extent of levothyroxine absorption into the bloodstream are similar for both formulations when administered under fasting conditions . This equivalence was consistent across different dosage strengths (50, 100, and 150 µg) of Tirosint, indicating that the soft capsule formulation can be reliably used in place of Synthroid without significant differences in drug exposure .

Adherence to Thyroid Hormone Replacement Therapy

Adherence Rates
Adherence to thyroid hormone replacement therapy is crucial for managing hypothyroidism effectively. A retrospective analysis of insurance claims data revealed that adherence rates vary significantly among different levothyroxine formulations. Synthroid was associated with higher adherence rates at both 6 and 12 months compared to other formulations, including Tirosint . Specifically, the likelihood of being adherent at 12 months was highest for Synthroid (OR = 1.44), followed by Levoxyl (OR = 1.20). In contrast, Tirosint had lower adherence rates (OR = 0.65) compared to generic levothyroxine .

Dissolution Profiles and Bioavailability

Dissolution Behavior
The dissolution profile of a drug is a critical factor influencing its bioavailability. A study examining the dissolution of levothyroxine from Synthroid, generic levothyroxine, and Tirosint found significant differences among these products. Tirosint demonstrated the most consistent dissolution profile, minimally affected by pH changes and the presence of surfactants, which are conditions that can alter drug absorption in the gastrointestinal tract . In contrast, Synthroid showed the most pH-dependent dissolution, which could lead to variability in drug absorption and bioavailability . This suggests that Tirosint may offer more stable and predictable absorption, potentially reducing the risk of bioequivalence issues.

Conclusion

In summary, both Tirosint and Synthroid are bioequivalent in terms of pharmacokinetics, making them interchangeable under fasting conditions. However, adherence rates are higher for Synthroid, which may influence long-term treatment outcomes. Additionally, Tirosint's consistent dissolution profile suggests it may offer more reliable absorption, particularly in patients with varying gastric pH levels. These factors should be considered when choosing between Tirosint and Synthroid for thyroid hormone replacement therapy.

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Most relevant research papers on this topic

Pharmacokinetic Equivalence of a Levothyroxine Sodium Soft Capsule Manufactured Using the New Food and Drug Administration Potency Guidelines in Healthy Volunteers Under Fasting Conditions

The new levothyroxine soft capsule formulated with stricter new FDA potency guidelines meets equivalence criteria in rate and extent of exposure under fasting conditions, making it suitable for clinical doses.

RCT

2011·

38citations

·P. Colucci et al.

Adherence to thyroid hormone replacement therapy: a retrospective, claims database analysis

Adherence to levothyroxine remains a concern among patients with hypothyroidism, with Synthroid showing the highest adherence at both 6 and 12 months, followed by Levoxyl, and Tirosint and Unithroid having lower adherence.

Observational Study

2018·

30citations

·Z. Hepp et al.

A comparative pH-dissolution profile study of selected commercial levothyroxine products using inductively coupled plasma mass spectrometry.

Variable dissolution of levothyroxine products can impact oral absorption and bioavailability, potentially causing bioequivalence problems between different products.

Highly Cited

2009·

113citations

·Dimple Pabla et al.

Food and levothyroxine administration in infants and children.

Levothyroxine should be administered on an empty stomach, four hours apart from antacids, iron, and calcium supplements, and crushed and suspended in water.

2010·

18citations

·P. Zeitler et al.

Improvements in Quality of Life and Thyroid Parameters in Hypothyroid Patients on Ethanol-Free Formula of Liquid Levothyroxine Therapy in Comparison to Tablet LT4 Form: An Observational Study

Liquid LT4 therapy provides better quality of life and thyroid hormone control for hypothyroid patients compared to tablet LT4 therapy, potentially due to better absorption.

Rigorous Journal

2021·

8citations

·Katarzyna Bornikowska et al.

Expert opinion on liquid L-thyroxine usage in hypothyroid patients and new liquid thyroxine formulation - Tirosint SOL [Opinia ekspertów dotycząca stosowania płynnej postaci lewotyroksyny oraz nowego preparatu Tirosint SOL u chorych na niedoczynność tarczycy].

Liquid L-thyroxine is more effective than tablet formulations for patients with malabsorption and the critically ill, but also shows promise in common therapy.

Systematic Review

2020·

9citations

·M. Gietka-Czernel et al.

Generic levothyroxine compared with synthroid in young children with congenital hypothyroidism.

Generic levothyroxine treatment in young children with congenital hypothyroidism resulted in similar or better control compared to Synthroid, as assessed by TSH variance and frequency of dosing adjustments.

Observational StudyRigorous Journal

2013·

14citations

·Jefferson P. Lomenick et al.

A Novel Levothyroxine Solution Results in Similar Bioavailability Whether Taken 30 or Just 15 Minutes Before a High-Fat High-Calorie Meal

A novel levothyroxine solution (Tirosint®-SOL) shows no significant difference in bioavailability when taken 15 minutes before a high-fat, high-calorie meal compared to the recommended 30-minute interval.

RCTRigorous Journal

2022·

8citations

·M. Ducharme et al.

Assessment of interchangeability of two brands of levothyroxine preparations with a third-generation TSH assay.

The two brands of levothyroxine, Synthroid and Levoxine, are clinically interchangeable, with no significant differences in clinical or laboratory changes in individual patients.

Observational Study

1995·

25citations

·D. Escalante et al.

Biopharmaceutical comparison of two levothyroxine sodium products.

Levothroid and Synthroid are therapeutically interchangeable, with any differences in bioavailability being clinically unimportant and both products meeting USP potency requirements.

RCT

1989·

10citations

·R. Blouin et al.

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