Effect of Age, Weight and Sex on Levothyroxine Pharmacokinetics

Georgetown University

Status and phase: Completed; Early Phase 1

Conditions: Hypothyroidism Primary

Treatments: Drug: Administration of stable Isotope labeled levothyroxine

Study type: Interventional

Funder types: Other

Identifiers

NCT03102177

2010-572

Details and patient eligibility

About

This study was a prospective, single-center, open-label, non-randomized, pharmacokinetic study using stable isotope carbon-13 labeled levothyroxine

Full description

Setting The study was conducted on the clinical research unit of an academic medical center.

Participants Adults of any age being treated with levothyroxine for hypothyroidism were studied.

Interventions A single dose of 13C- LT4 was administered to hypothyroid subjects taking levothyroxine replacement.

Main Outcomes and Measures Eighteen serial plasma samples were collected. One sample was obtained before the 13C- LT4 dose and the remainder over the 312-hour period post-dosing. 13C- LT4 concentration was quantified using validated liquid chromatography tandem mass spectrometry methods. Pharmacokinetic analysis was conducted using linear log trapezoidal non-compartmental analysis using Phoenix 6.4.

Enrollment: 41 patients

Sex: All

Ages: 21+ years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• age >21 years at the time of consent
• euthyroidism while undergoing treatment with LT4
• no other serious illness
• ability to give written informed consent.

Exclusion criteria

• baseline hematocrit lower than 28.0%
• TSH greater than 4.5 mIU/L
• kidney dysfunction
• concomitant use of drugs that affect thyroidal axis interactions

Trial design

Primary purpose: Other

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)

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41 participants in 1 patient group

Stable isotope arm

Experimental group

Description:

Measurement of blood levels of labelled levothyroxine after administration of single oral dose of stable isotope levothyroxine

Treatment:

Drug: Administration of stable Isotope labeled levothyroxine