Hi Paul

Digoxin has a relatively long half-life, so after the initial distribution period (approx. 6h), the variation across the rest of the dosage interval is small – see below, taken from Nicholson et al., Br J Clin Pharmacol 1980; 9: 467-70.

Nicholson et al. concluded that sampling 11h post-dose was ideal, but most people’s practice is that anything after 6h is a reasonable estimate of average tissue concentration. You could use the data in the article to calculate an average relationship between the 6-8h calculation and the 12h concentration if you wanted to avoid a validation exercise. Or you could ask Roche for the evidence underpinning their insistence on 12h.

Hope that helps

Mike

Sent from Mail for Windows 10

Good afternoon,

I would appreciate it if anyone has come across and overcome the following problem. In Belfast we run a digoxin assay on a Roche Cobas system. Conventional practice has been to analyse samples taken 6-8 hours post-dosing, however the Roche literature stipulates testing 12 hours post-dosing.

A 6 hour level is reasonably convenient, since an inpatient having digoxin administered at 10 am can undergo venepuncture within 'office hours'. 12 hour levels are more difficult, particularly when dealing with an outpatient or patient in the community.

Has anyone come across this problem and solved it without having to do a major validation exercise?

Kind regards,

Paul Hamilton

Clinical Biochemistry

Belfast Health and Social Care Trust

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