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Differences in color discrimination between three cardioactive glycosides
1Department of Clinical Pharmacology, Medical Academy Erfurt, GDR.
Insights
Digoxin, but not digitoxin or pengitoxin, impairs color discrimination in heart failure patients. This effect is dose-dependent and linked to digoxin
Area of Science:
- Cardiology
- Pharmacology
- Ophthalmology
Background:
- Congestive heart failure (CHF) patients often receive digitalis glycosides.
- Potential visual side effects of these medications require investigation.
- Color vision is a sensitive indicator of neurological function.
Purpose of the Study:
- To compare the effects of digitoxin, pengitoxin, and digoxin on color discrimination in CHF patients.
- To correlate color discrimination impairment with plasma glycoside levels and patient age.
- To identify specific digitalis glycosides that may affect visual perception.
Main Methods:
- Farnsworth-Munsell 100 Hue (FM 100) test administered to 100 CHF patients on digitoxin, pengitoxin, or digoxin, and 72 controls.
- Radioimmunoassay used to measure plasma glycoside levels.
- Total Error Score (TES) correlated with plasma levels and age.
Main Results:
- Digoxin significantly increased TES in therapeutically relevant plasma concentrations, indicating impaired color discrimination.
- Digitoxin and pengitoxin did not show significant differences in TES compared to controls, even with age-dependent increases.
- Observed differences attributed to variations in glycoside volume of distribution and plasma protein binding.
Conclusions:
- Digoxin, unlike digitoxin and pengitoxin, demonstrably impairs color discrimination ability in CHF patients.
- Visual side effects, specifically color vision deficits, should be considered with digoxin therapy.
- Pharmacokinetic differences between digitalis glycosides explain their varying impacts on color vision.
Abstract:
Color discrimination ability of 100 in-patients suffering from congestive heart failure and treated with digitoxin (D), pengitoxin (P), or digoxin (Dg) was determined with the Farnsworth-Munsell 100 Hue test (FM 100) and compared with the color discrimination of 72 in-patients who were not treated with digitalis glycosides (control group C). Parallel to the performance of the FM 100, the glycoside plasma level was measured by radioimmunoassay. The total error score (TES) of the FM 100 was correlated with the glycoside plasma level and the patient's age. In the C as well as in the D or P groups up to 172 errors and in the Dg group up to 586 errors were observed. With the exception of Dg, no differences were observed between the regression lines indicating an age-dependent increase in TES even under D or P treatment. In contrast to the two glycosides, Dg enhances the TES in therapeutically relevant plasma concentrations. The differences between the glycosides are due to differences in their volume of distribution and their plasma protein binding.