Comparison of steady-state serum concentrations of digoxin in tablets (Lanoxin) and capsules (Lanoxicaps) in the elderly.
The bioavailability of digoxin in solution (Lanoxicaps, 90-100 percent) is superior to that of Lanoxin tablets (60-80 percent) in young healthy volunteers. The alleged bioequivalence of digoxin in tablets (Lanoxin 0.25, 0.125 mg) and capsules (Lanoxicaps 0.2, 0.1 mg) was studied in 20 elderly inpatients (14 women, 6 men, aged 84 +/- 5 years), treated with digoxin for atrial fibrillation. In a crossover design, steady-state digoxin concentrations were measured in 16 patients after once-daily administration of Lanoxin 0.125 mg or Lanoxicaps 0.1 mg, each for at least ten days. Four other patients took Lanoxin 0.25 mg and Lanoxicaps 0.2 mg successively. The steady-state digoxin concentrations were statistically significantly different, being 1.3 +/- 0.5 nmol/L for Lanoxin and 0.9 +/- 0.4 nmol/L for Lanoxicaps (p = 0.003). Whereas in young healthy volunteers the bioavailability of digoxin from Lanoxicaps (90-100 percent) exceeds that from Lanoxin (80 percent), in elderly patients the absorption appears to be similar. This suggests a lower than expected bioavailability of Lanoxicaps, which may result in subtherapeutic serum concentrations.
Pouwels
M J
MJ
Department of Medicine, University Hospital St. Radboud, Nijmegen, The Netherlands.
Hooymans
P M
PM
van der Aa
G C
GC
Gribnau
F W
FW
D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000378:metabolism; D001682:Biological Availability; D002214:Capsules; D004077:Digoxin / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D013607:Tablets; D013810:Therapeutic Equivalency
D002214:Capsules; D013607:Tablets; D004077:Digoxin