Clinical Application of Serum Digitoxin Levels

Abstract

A simple, rapid, and reliable determination of plasma digitoxin levels is now available for clinical use. It can be determined in any clinical laboratory capable of determining a serum phosphorus if ATPase enzyme is available. Maintenance plasma levels range between 10 and 40 mµg/ml with a mean value of 25 mµg/ml. There is overlapping of maintenance and toxic serum levels in the higher ranges. Values over 45 mµg/ml warrant careful evaluation for digitalis intoxication. Maintenance plasma levels can be achieved with or without the usual digitalizing dosage if time is not a factor. The daily regression rate is variable in cases of digitalis intoxication following drug withdrawal. ECG changes (the degree of ST-segment depression, PR-interval prolongation, and multifocal premature contractions) were not good criteria for digitalis intoxication, although PR intervals above 0.24 sec consistently correlated with high plasma digitoxin levels. Variable second and third degree A-V block associated with mental confusion was a frequent presenting feature of digitalis toxicity.

Enzymatic determination of cardiac glycosides

“…Plasma extracts obtained from blood containing a variety of drugs, including ethacrynic acid, were shown to have no effect on the Na,K-ATPase system (20). This finding is substantiated by the successful clinical application of methods based on the inhibition of the Na,K-ATPase (2,9). The procedure described here is presently applied to estimate plasma levels of CG in man in a study on drug equivalency.…”

“…average plasma levels of digoxin and digitoxin (the two most commonly used CG) in fully digitalized patients were reported to be 1.5 and 25 rig/ml, respectively (1,2). Various attempts have been made to fulfill these analytical requirements (%6).…”

Digitoxin Studies

“…The serum concentration for patients on maintenance therapy is reported to be about 10-50 ngjml (Table III). At present the most rapid determination is the direct ATPase method measuring phosphate release (1,2). Otherwise the choice between the methods must depend on experience and equipment (7).…”

Συμβολη Εις Την Αναπτυξιν Ραδιοχημικης Μεθοδου Προσδιορισμου Του Ν5 Μεθυλ-Τετραυδροφυλλικου Οξεος Και Παραγωγων Εις Τον Ανθρωπινον Ορον

“…Τοιουτοτρόπως άνεπτύχθησαν μέθοδοι προσ διορισμού ορμονικών πολυπεπτιδίων, ώς τής κορτικοτροπίνης (AC ΤΗ) 3 , παραθορμόνης (ΡΤΗ)*, γλυκογόνου 5 , θυρεοειδοτρόπου ορμόνης (TSΗ) 6 , χοριονικής γοναδοτροπίνης (HCC) 1 , άγγειοτενσίνης 8 , θυρεοκαλσιτονίνης (HTC) 9 , Ινσουλίνης 10 ', αυξητικής ορμόνης (HGH) 11 , οξυτοκίνης 12 , μελανοτρόπου 13 και θυλακιοτρόπου ορμόνης 1 * και τής γαστρίνης 15 . Ή αυτή αρχή επεξετάθη εις τον προσδιορισμόν μικρομοριακών ουσιών με βιολογικήν δράσιν, ώς τής τε στοστερόνης 16 , μεταβο)ακώς δραστικών κορτικοειδών 17 , οίστραδιόλης 18 , θυ ροξίνης, 19 τριιωδοθυρονίνης και βιταμίνης Β12 20 καί φαρμάκων εις τον άνθρώ πινον ορόν, ώς τής διγοξίνης 21 και διγιτοξίνης 22 .…”