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Tissue and erythrocyte distribution of digoxin in infants
Insights
Infants show higher digoxin uptake in heart muscle compared to adults, with a larger volume of distribution. This explains why infants require higher therapeutic digoxin doses.
Area of Science:
- Pharmacology
- Pediatrics
- Clinical Pharmacy
Background:
- Digoxin is a crucial medication for treating heart conditions in infants.
- Understanding digoxin distribution is vital for optimizing pediatric dosing.
- Previous studies have not fully elucidated digoxin pharmacokinetics in neonates.
Purpose of the Study:
- To investigate the distribution of digoxin in various tissues of infant subjects.
- To compare digoxin tissue-to-serum concentration ratios in infants versus adults.
- To explore the relationship between digoxin distribution and therapeutic dosing in infants.
Main Methods:
- Studied digoxin distribution in myocardium, skeletal muscle, erythrocytes, and plasma in 19 infants.
- Analyzed the linear relationship between myocardium and serum concentrations.
- Compared erythrocyte:plasma concentration ratios during digitalization and maintenance therapy.
Main Results:
- A linear relationship between digoxin concentrations in myocardium and serum was observed, with no saturation up to 8.6 ng/ml.
- Myocardium uptake of digoxin was approximately double in infants compared to adults.
- Erythrocyte:plasma digoxin ratios were lower during digitalization and significantly higher in infants than adults during maintenance therapy.
Conclusions:
- Infants exhibit a greater apparent volume of distribution for digoxin.
- Findings suggest that increased digoxin tissue distribution in infants necessitates higher therapeutic doses.
- This pharmacokinetic understanding is essential for safe and effective digoxin therapy in pediatric populations.
Abstract:
The distribution of digoxin in the myocardium, skeletal muscle, erythrocytes, and plasma (or serum) was studied in 19 infants. There was a linear relationship between myocardium and serum concentrations and no saturation was observed over the serum concentration range of 0.5-8.6 ng/ml. Myocardium uptake of digoxin was nearly twice as great in infants as in adults at any given serum concentration. Erythrocyte: plasma concentration ratios of digoxin were one-third smaller during digitalization than during maintenance digoxin therapy. The latter ratios were also three times greater in infants than found previously in adults. Their findings are consistent with a greater apparent volume of distribution of digoxin in infants and may partly explain the unusually large therapeutic doses needed in infants.