Probable interaction between levothyroxine and ritonavir: case report and literature review
Abstract
PURPOSE: A case of probable interaction of levothyroxine and ritonavir is presented along with a review of the relevant literature and recommendations on clinical management. SUMMARY: A 37-year-old woman with human immunodeficiency virus infection who had recently undergone thyroidectomy for a benign multinodular goiter presented to a clinic with hypothyroidism (she was also found to be pregnant), and treatment with levothyroxine 75 μg daily was initiated. While receiving antiretroviral therapy (abacavir-lamivudine and lopinavir-ritonavir) during pregnancy, the patient had persistently elevated serum thyroid-stimulating hormone (TSH) concentrations (up to 125.89 μIU/mL) despite gradual escalation of the levothyroxine dosage to 175 μg daily. An interaction between ritonavir and levothyroxine was suspected, and dolutegravir was substituted for lopinavir-ritonavir. Within 4 months, the TSH concentration had normalized. The daily levothyroxine dose was tapered over a 5-month period and stabilized at 125 μg, and TSH concentrations remained within the normal range over an 18-month follow-up period. Scoring of the case using the Drug Interaction Probability Scale yielded a score of 6 out of 11, indicating a probable interaction between levothyroxine and ritonavir. A literature search identified 4 reported cases of interactions involving levothyroxine and ritonavir. CONCLUSION: A potentially serious and underrecognized drug interaction between ritonavir and levothyroxine was observed in a pregnant woman with postthyroidectomy-related hypothyroidism. This case and a review of other cases reported in the literature indicate that higher-than-usual doses of levothyroxine may be required in patients who are taking ritonavir concurrently.
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The induction of cytochrome P450 enzyme activity in the liver by statins or protease inhibitors can accelerate the catabolism of LT4, and hence decrease serum T4 levels.
“The induction of cytochrome P450 enzyme activity in the liver by statins or protease inhibitors can accelerate the catabolism of LT4, and hence decrease serum T4 levels (84, 85).”
From Levothyroxine: conventional and novel drug delivery formulations. (2023) · cites this paper as [85]
Hypothyroid HAART-treated patients needing increased L-T4 doses were reported with ritonavir, abacavir-lamivudine and lopinavir-ritonavir, and lopinavir/ritonavir plus zidovudine and lamivudine.
“Hypothyroid HAART-treated patients needing increased L-T4 doses were reported (53–55). HAART drugs were ritonavir (48), abacavir–lamivudine and lopinavir–ritonavir (54), and lopinavir/ritonavir plus zidovudine and lamivudine (55).”
From L-T4 therapy in the presence of pharmacological interferents (2020) · cites this paper as [54]
Switch from lopinavir/ritonavir to nelfinavir failed to achieve euthyroidism, which was restored when dolutegravir was substituted for lopinavir-ritonavir.
“Switch from lopinavir/ritonavir to nelfinavir failed to achieve euthyroidism (55), which was restored when dolutegravir was substituted for lopinavir–ritonavir (54).”
From L-T4 therapy in the presence of pharmacological interferents (2020) · cites this paper as [54]
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Levothyroxine: conventional and novel drug delivery formulations.
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L-T4 therapy in the presence of pharmacological interferents
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- Authors
- Sahajpal, R., Ahmed, R. A., Hughes, C. A., & Foisy, M. M.
- Affiliations
- Rockyview General Hospital (CA)
- University of Alberta (CA)
- Royal Alexandra Hospital (CA)
- Corresponding author
- Foisy, Michelle M.
- Venue
- American Journal of Health-System Pharmacy
- Publisher
- Oxford University Press (OUP)
- Published
- 2012-04-15
- Volume
- 74
- Issue
- 8
- Pages
- 587-592
- ISSN
- 1079-2082 (ISSN-L)
- 1535-2900
- OpenAlex
- W2605246488
- Cited by
- 13
- References
- 22
- Citations by year
- 2026: 1 · 2024: 2 · 2023: 2 · 2022: 2 · 2021: 1 · 2020: 2 · 2019: 1 · 2017: 2
- FWCI
- 0.00
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- American Journal of Health-System Pharmacy (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Infectious Diseases › HIV/AIDS drug development and treatment
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmacogenetics and Drug Metabolism
- Keywords
- levothyroxine, ritonavir, drug interactions, antiretroviral therapy, HIV infection, pregnancy, hypothyroidism, thyroidectomy, multinodular goiter, thyroid-stimulating hormone, lopinavir/ritonavir, dolutegravir, Drug Interaction Probability Scale, dose adjustment
- MeSH terms
- Adult, Dose-Response Relationship, Drug, Drug Interactions, Female, Humans, Hypothyroidism, Thyroxine, HIV Infections, HIV Protease Inhibitors, Ritonavir
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