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Prescribing digoxin in geriatric units: the unexplained variability in dosage requirements
R J Dobbs1, J P Royston, C J O'Neill
1Medicine for the Elderly, Barnet General Hospital, Hertfordshire.
European Journal of Clinical Pharmacology
|January 1, 1987
Summary
Digoxin dosage needs vary significantly in elderly patients, challenging the idea of a homogeneous population. Individualized dosing is crucial, as standard pharmacokinetic models show limited predictive value for geriatric patients.
Area of Science:
- Pharmacology
- Geriatric Medicine
- Clinical Pharmacy
Background:
- Physicians debate whether geriatric patients have uniform digoxin dosage needs or require individualized pharmacokinetic approaches.
- Digoxin is a common maintenance medication for elderly patients, necessitating precise dosing to ensure efficacy and safety.
Purpose of the Study:
- To investigate digoxin dosage requirements in geriatric unit inpatients.
- To compare digoxin dosing variability in geriatric patients versus other adult units.
- To assess the predictive value of clinical variables (serum creatinine, sex, age, body weight) on digoxin dose.
Main Methods:
- Studied 60 inpatients in Geriatric Units receiving maintenance digoxin.
- Calculated the standardized dose required for a mean steady-state serum digoxin concentration of 1.6 nmol/L.
- Compared results with 129 patients from other adult units, analyzing four dose estimates per patient.
Main Results:
- A threefold range in standardized digoxin dose covered approximately 85% of patients in both geriatric (62.5-187.5 µg/day) and adult units (125-375 µg/day).
- Serum creatinine, sex, age, and body weight had limited predictive value for standardized digoxin dose in geriatric patients.
- A distinct subgroup of geriatric inpatients required exceptionally high standardized digoxin doses.
Conclusions:
- Geriatric patients exhibit significant variability in digoxin dosage requirements, refuting the concept of a homogeneous population.
- Standard pharmacokinetic parameters are insufficient for accurately predicting digoxin dose needs in many elderly patients.
- Further investigation is needed to understand the factors contributing to extremely high digoxin dose requirements in a subset of geriatric patients.