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Drug Interactions between fosphenytoin and Lanoxin

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

digoxin fosphenytoin

Applies to: Lanoxin (digoxin) and fosphenytoin

MONITOR: Limited clinical data suggest that hydantoins may reduce digoxin serum levels. The mechanism of this interaction is unknown. Although phenytoin has been used in the treatment of digitalis-induced arrhythmias, it has been associated with cardiac arrest in patients with marked heart block.

MANAGEMENT: If these drugs are used concomitantly, close monitoring for clinical and laboratory evidence of altered digitalis effect is recommended. Occasionally, increases in the digoxin dosage may be necessary. The clinician should be aware that the risk of digoxin toxicity may be increased when a hydantoin is discontinued and should consider monitoring the patient more closely for those effects. Phenytoin should be avoided in patients with marked digoxin-induced heart block or bradycardia.

References (13)
  1. Rumack BH, Wolfe RR, Gilfrich H (1974) "Phenytoin (diphenylhydantoin) treatment of massive digoxin overdose." Br Heart J, 36, p. 405-8
  2. Rameis H (1985) "On the interaction between phenytoin and digoxin." Eur J Clin Pharmacol, 29, p. 49-53
  3. Rameis H (1992) "The importance of prospective planning of pharmacokinetic trials. Considerations of studies on the phenytoin-digoxin-(P-D) and phenytoin-digitoxin-(P-DT) interaction." Int J Clin Pharmacol Ther Toxicol, 30, p. 528-9
  4. Viukari NM, Aho K (1970) "Digoxin-phenytoin interaction." Br Med J, 2, p. 51
  5. Solomon HM, Abrams WB (1972) "Interactions between digitoxin and other drugs in man." Am Heart J, 83, p. 277-80
  6. Allonen H (1977) "The effect of phenytoin on the tissue concentrations of digoxin in the rat." Acta Pharmacol Toxicol (Copenh), 41, p. 481-8
  7. Allonen H, Iisalo E, Nuortio L (1975) "Effect of reserpine, desipramine and phenytoin on digoxin induced arrhythmias and myocardial uptake of digoxin in guinea pigs." Acta Pharmacol Toxicol (Copenh), 37, p. 8-16
  8. Rameis H (1992) "The importance of prospective planning of pharmacokinetic trials." Int J Clin Pharmacol Ther Toxicol, 30, p. 528-9
  9. Solomon HM, Reich S, Spirt N, Abrams WB (1971) "Interactions between digitoxin and other drugs in vitro and in vivo." Ann N Y Acad Sci, 179, p. 362-8
  10. (2001) "Product Information. Lanoxin (digoxin)." Glaxo Wellcome
  11. (2001) "Product Information. Cerebyx (fosphenytoin)." Parke-Davis
  12. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  13. Cerner Multum, Inc. "Australian Product Information."

Drug and food interactions

Minor

digoxin food

Applies to: Lanoxin (digoxin)

Administration of digoxin with a high-fiber meal has been shown to decrease its bioavailability by almost 20%. Fiber can sequester up to 45% of the drug when given orally. Patients should be advised to maintain a regular diet without significant fluctuation in fiber intake while digoxin is being titrated.

Grapefruit juice may modestly increase the plasma concentrations of digoxin. The mechanism is increased absorption of digoxin due to mild inhibition of intestinal P-glycoprotein by certain compounds present in grapefruits. In 12 healthy volunteers, administration of grapefruit juice with and 30 minutes before, as well as 3.5, 7.5, and 11.5 hours after a single digoxin dose (0.5 mg) increased the mean area under the plasma concentration-time curve (AUC) of digoxin by just 9% compared to administration with water. Moreover, P-glycoprotein genetic polymorphism does not appear to influence the magnitude of the effects of grapefruit juice on digoxin. Thus, the interaction is unlikely to be of clinical significance.

References (2)
  1. Darcy PF (1995) "Nutrient-drug interactions." Adverse Drug React Toxicol Rev, 14, p. 233-54
  2. Becquemont L, Verstuyft C, Kerb R, et al. (2001) "Effect of grapefruit juice on digoxin pharmacokinetics in humans." Clin Pharmacol Ther, 70, p. 311-6

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

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