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[Pharmacokinetics of digoxin in hyperthyroidism. Effect of methimazole]
Maria Izbicka1, Teresa Gasińska, Renata Dec
1Wojewódzka Poradnia Endokrynologiczna w Katowicach.
Insights
Hyperthyroid patients exhibit altered digoxin pharmacokinetics, with lower serum concentrations and faster elimination. Methimazole treatment did not impact these changes, suggesting thyroid status is key.
Area of Science:
- Pharmacology
- Endocrinology
- Cardiology
Background:
- Cardiovascular issues are key in hyperthyroidism.
- Digoxin efficacy is reduced in hyperthyroid patients.
- Understanding digoxin pharmacokinetics in hyperthyroidism is crucial.
Purpose of the Study:
- Compare digoxin pharmacokinetics in hyperthyroid vs. euthyroid patients.
- Investigate methimazole's effect on digoxin pharmacokinetics.
- Assess methimazole-induced euthyroidism's impact on digoxin.
Main Methods:
- Evaluated single oral dose digoxin pharmacokinetics in 28 hyperthyroid patients and 15 controls.
- Assessed digoxin pharmacokinetics with simultaneous digoxin and methimazole administration.
- Re-evaluated digoxin pharmacokinetics in 12 patients after becoming euthyroid.
Main Results:
- Hyperthyroid patients had lower serum digoxin concentrations and shorter half-lives.
- Area under the curve (AUC) for digoxin was significantly smaller in hyperthyroid patients.
- Methimazole administration did not alter digoxin pharmacokinetics.
Conclusions:
- Digoxin pharmacokinetics differ significantly between hyperthyroid and euthyroid individuals.
- Methimazole does not alter digoxin pharmacokinetics.
- Thyroid status directly influences digoxin's absorption and elimination.
Introduction:
Cardiovascular abnormalities may be the only manifestations of overt hyperthyroidism. In patients with heart failure and atrial fibrillation digoxin can be beneficial in controlling the symptoms and signs, but hyperthyroid patients show an impaired response or even resistance to digoxin treatment. The aim of the study is to establish: 1. Are there any differences in the pharmacokinetics of a single oral dose of digoxin between hypertyroid and euthyroid patients? 2. Does simultaneous administration of digoxin and methimazole affect the pharmacokinetics of a single oral dose of dogoxin? 3. Does methimazole-induced euthyroidism change the pharmacokinetics of a single oral dose of digoxin?
Material And Methods:
The subject of the study were 28 patients with hyperthyroidism and 15 healthy persons. We evaluated the pharmacokinetics of a single oral dose of digoxin. Moreover we evaluated pharmacokinetics of a single dose of digoxin after simultaneous administration of digoxin and methimazole in 12 patients and 12 methimazole treated patients werere-assessed once they had become euthyroid.
Results:
Hyperthyroid patients showed significantly lower serum digoxin concentrations, shorter T1/2 beta and a significantly smaller area under the concentration curve (AUC) that the control group. Administration of methimazole did not affect digoxin pharmacokinetics.
Conclusions:
In hyperthyroid patients: 1. the pharmacokinetics of a single oral dose of digoxin does differ from that observed in healthy subjects. 2.methimazole do not alter digoxin pharmacokinetics.
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