Digoxin toxicit in chronic renal failure: treatment by multiple dose activated charcoal intestinal dialysis

1 Digoxin toxicity can result from overdose or iatrogenic causes, especially if renal function is impaired. 2 We present a case of digoxin toxicity presenting with severe bradycardia and hypotension in a 66 year old man with chronic renal failure. Regular haemodia lysis had, as predicted, failed to reduce his plasma digoxin concentration. Digoxin specific antibody fragments (Fab) were not readily available and their use was probably inappropriate as they are normally renally eliminated. 3 The patient was successfully treated by two prolonged courses of intestinal dialysis with repeated doses of activated charcoal over 48 and 72 h and totaling 400 g and 600 g, respectively. However, the patient found the activated charcoal extremely unpalatable. 4 Multiple dose activated charcoal intestinal dialysis (MDACID) has been recently advocated for use in a wide range of poisonings. The technique takes advantage of the large surface area of the small intestine to eliminate drugs and metabolites, over several days if necessary. The pharmacokinetics of digoxin toxicity in chronic renal failure make intest inal dialysis an appropriate method of treatment but the realisation of the true potential of this technique awaits a more palatable absorbent or formulation.

Digoxin and Cimetidine: Investigation of the Potential for a Drug Interaction

1 The potential for a pharmacokinetic interaction between digoxin and cimetidine was investigated in a series of studies. 2 In a single-dose cross-over study in healthy volunteer subjects cimetidine increased the area under the plasma digoxin concentration curve and the peak plasma digoxin concentration. 3 In a repeated-dose study in healthy volunteer subjects taking digoxin 0.25 mg daily, co-administration of cimetidine resulted in an average increase in plasma digoxin concentration of 0.15 ng/ml. 4 In a repeated-dose study in healthy volunteer subjects taking digoxin 0.5 mg daily, co-administration of cimetidine resulted in an average increase in plasma digoxin concentration of 0.19 ng/ml. 5 In a repeated-dose study in patients receiving long-term digoxin therapy for atrial fibrillation co-administration of cimetidine had no significant effect on plasma digoxin concentrations. 6 We have shown that co-administration of cimetidine and digoxin in volunteer subjects causes a statistically significant but small increase in plasma digoxin concentration but no such increase was found in patients. We conclude that it is doubtful that this interaction is of any clinical significance.