Читать книгу Clinical Pharmacology and Therapeutics - Группа авторов - Страница 45

Digoxin has linear pharmacokinetics; therefore, the new dose can be determined by simple proportion. Table 1.5 shows that there are three dosage options for Mr A.R. A reduction to 125 μg/day is the most obvious first choice, but further adjustment (up or down) could be made if necessary on clinical grounds (e.g. poor control of atrial fibrillation or persistence of adverse effects).

Comment. This case illustrates the importance of sampling time for the correct interpretation of digoxin concentrations. Although digoxin is traditionally prescribed to be taken in the morning, changing to a night‐time dose can reduce the chances of samples being withdrawn during the distribution phase. Digoxin has a long elimination half‐life (50–100 hours) and elimination is slow beyond 6 hours after the dose. If samples are taken at steady state, dosage adjustment can be performed by simple proportion.