Digoxin specific antibody fragments (Digibind) in digoxin toxicity

Dear editor,

In article on ‘Digoxin specific antibody fragments (Digibind) in
digoxin toxicity’, Dr Dorothy Ip, Dr H Syed and Dr Cohen presented a case
of elderly woman presented with renal impairment, hyperkalemia and digoxin
toxicity who had treatment with digibind (digoxin – antibody fragments).

There are a few questions that, I think, need answering. I would like
to know the values of electrolytes (including creatinine) on presentation
in this patient and what did the baseline ECG show. Did ECG show sings of
hyperkalemia? Did the patients have other symtoms to suggest digoxin
toxicity (GI or visual symtoms)? Then authors did not comment on the
treatment of hyperkalemia as it might have contributed to the digoxin
toxicity (i-e calcium administration).

It is said that that calcium administered in the setting of digoxin
toxicity can potentiate the effect of digoxin and may cause arrhythmia or
cardiac arrest (1),(as in this case patient developed bradyarrythmia after
treatment of hyperkalemia, but it is not clear from the article whether
this patient had IV calcium or not), however this fact has been debatable
(5,6). Secondly, as digoxin normally competes with K+ ions for the same
binding site on the Na+/K+ ATPase pump, lowering of potassium level down
(with conventional measures) in setting of digoxin toxicity can
theoretically increase digoxin cardiac sensitivity.

Thirdly digoxin toxicity is associated with hyperkalemia (2,3).
Therapy with digoxin antibody (Fab) fragments is indicated in this setting
(4) and it will reduce the serum potassium (1).

There should be high index of suspicion of digoxin toxicity in
digoxin taking patients who present with renal failure and hyperkalemia.

References;

1) M Davey; Calcium for hyperkalemia in digoxin toxicity (Emergency
Medicine Journal 2002;19:183; doi:10.1136/emj.19.2.183)

2) Cardiac glycoside toxicity is frequently associated with
hyperkalemia and dysrhythmias in patients with renal insufficiency. J
Toxicol Clin Toxicol. 2003;41(4):373-6; Treatment of hyperkalemia in a
patient with unrecognized digitalis toxicity (Van Deusen SK, Birkhahn RH,
Gaeta TJ).

3) Ann Emerg Med. 1996 Oct;28(4):440-1. Hyperkalemia and digoxin
toxicity in a patient with kidney failure. Fenton F, Smally AJ, Laut J.

4) GlaxoSmithKline. Digibind prescribing information. 2003.
http://us.gsk.com/products/assets/us_digibind.pdf.

5) J Emerg Med. 2009 Feb 5. The Effects of Intravenous Calcium in
Patients with Digoxin Toxicity;(Levine M, Nikkanen H, Pallin DJ).

6) J Toxicol Clin Toxicol. 2004;42(4):337-42: The effect of calcium
chloride in treating hyperkalemia due to acute digoxin toxicity in a
porcine model (Hack JB, Woody JH, Lewis DE, Brewer K, Meggs WJ).

(faisalkhan@doctors.org.uk)

Competing interests:
None declared