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Drug Interactions between Theophylline KI and tolvaptan

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

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Interactions between your drugs

Moderate

potassium iodide tolvaptan

Applies to: Theophylline KI (potassium iodide / theophylline) and tolvaptan

MONITOR: Coadministration with tolvaptan can potentiate the risk of hyperkalemia in patients treated with other drugs that are known to increase serum potassium. Tolvaptan alone can increase serum potassium by causing an acute reduction of the extracellular fluid volume. In clinical studies, adverse reactions of hyperkalemia were approximately 1% to 2% higher when tolvaptan was used concomitantly with ACE inhibitors, angiotensin II receptor antagonists, or potassium sparing diuretics compared to administration of these medications with placebo.

MANAGEMENT: Serum potassium levels should be checked regularly during concomitant therapy with tolvaptan and other agents that can increase serum potassium such as ACE inhibitors, angiotensin II receptor antagonists, potassium-sparing diuretics, aldosterone antagonists, and miscellaneous agents like cyclosporine, heparin, tacrolimus, and trimethoprim. Particular caution is warranted in patients with renal impairment, diabetes, old age, severe or worsening heart failure, or dehydration. Patients should be advised to seek medical attention if they experience signs and symptoms of hyperkalemia such as nausea, vomiting, weakness, listlessness, tingling of the extremities, paralysis, confusion, weak pulse, and a slow or irregular heartbeat.

References

  1. "Product Information. Samsca (tolvaptan)." Otsuka American Pharmaceuticals Inc (2009):

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Drug and food interactions

Moderate

theophylline food

Applies to: Theophylline KI (potassium iodide / theophylline)

GENERALLY AVOID: Coadministration with caffeine may increase the serum concentrations of theophylline. The proposed mechanism involves competitive inhibition of theophylline metabolism via CYP450 1A2, as well as metabolic conversion of caffeine to theophylline in vivo and saturation of theophylline metabolism at higher serum concentrations. In six healthy male volunteers (all smokers), serum concentrations of theophylline (administered as aminophylline 400 mg single oral dose) were significantly higher following consumption of caffeine (2 to 7 cups of instant coffee over 24 hours, equivalent to approximately 120 to 630 mg of caffeine) than after caffeine deprivation for 48 hours. Caffeine consumption also increased the apparent elimination half-life of theophylline by an average of 32% and reduced its total body clearance by 23%. In another study, steady-state concentration and area under the concentration-time curve of theophylline (1200 mg intravenously over 24 hours) increased by 23% and 40%, respectively, in eight healthy volunteers following administration of caffeine (300 mg orally three times a day).

MANAGEMENT: Given the narrow therapeutic index of theophylline, patients should limit or avoid significant fluctuations in their intake of pharmacologic as well as dietary caffeine.

ADJUST DOSING INTERVAL: Administration of theophylline with continuous enteral nutrition may reduce the serum levels or the rate of absorption of theophylline. The mechanism has not been reported. In one case, theophylline levels decreased by 53% in a patient receiving continuous nasogastric tube feedings and occurred with both theophylline tablet and liquid formulations, but not with intravenous aminophylline.

MANAGEMENT: When administered to patients receiving continuous enteral nutrition , some experts recommend that the tube feeding should be interrupted for at least 1 hour before and 1 hour after the dose of theophylline is given; rapid-release formulations are preferable, and theophylline levels should be monitored.

References

  1. Jonkman JH, Sollie FA, Sauter R, Steinijans VW "The influence of caffeine on the steady-state pharmacokinetics of theophylline." Clin Pharmacol Ther 49 (1991): 248-55
  2. Sato J, Nakata H, Owada E, Kikuta T, Umetsu M, Ito K "Influence of usual intake of dietary caffeine on single-dose kinetics of theophylline in healthy human subjects." Eur J Clin Pharmacol 44 (1993): 295-8
  3. Wohlt PD, Zheng L, Gunderson S, Balzar SA, Johnson BD, Fish JT "Recommendations for the use of medications with continuous enteral nutrition." Am J Health Syst Pharm 66 (2009): 1438-67

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Moderate

tolvaptan food

Applies to: tolvaptan

GENERALLY AVOID: Grapefruit juice may significantly increase the plasma concentrations of tolvaptan. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. According to the product labeling, administration of tolvaptan with grapefruit juice resulted in a 1.8-fold increase in tolvaptan systemic exposure. The clinical significance is unknown, although increased pharmacologic effects may be expected. Too rapid correction of hyponatremia increases the risk of osmotic demyelination syndrome, which is associated with dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma, and death.

MANAGEMENT: Patients treated with tolvaptan should avoid consumption of grapefruits and grapefruit juice.

References

  1. "Product Information. Samsca (tolvaptan)." Otsuka American Pharmaceuticals Inc (2009):

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Moderate

theophylline food

Applies to: Theophylline KI (potassium iodide / theophylline)

GENERALLY AVOID: Coadministration with caffeine may increase the serum concentrations of theophylline. The proposed mechanism involves competitive inhibition of theophylline metabolism via CYP450 1A2, as well as metabolic conversion of caffeine to theophylline in vivo and saturation of theophylline metabolism at higher serum concentrations. In six healthy male volunteers (all smokers), serum concentrations of theophylline (administered as aminophylline 400 mg single oral dose) were significantly higher following consumption of caffeine (2 to 7 cups of instant coffee over 24 hours, equivalent to approximately 120 to 630 mg of caffeine) than after caffeine deprivation for 48 hours. Caffeine consumption also increased the apparent elimination half-life of theophylline by an average of 32% and reduced its total body clearance by 23%. In another study, steady-state concentration and area under the concentration-time curve of theophylline (1200 mg intravenously over 24 hours) increased by 23% and 40%, respectively, in eight healthy volunteers following administration of caffeine (300 mg orally three times a day).

MANAGEMENT: Given the narrow therapeutic index of theophylline, patients should limit or avoid significant fluctuations in their intake of pharmacologic as well as dietary caffeine.

References

  1. Jonkman JH, Sollie FA, Sauter R, Steinijans VW "The influence of caffeine on the steady-state pharmacokinetics of theophylline." Clin Pharmacol Ther 49 (1991): 248-55
  2. Sato J, Nakata H, Owada E, Kikuta T, Umetsu M, Ito K "Influence of usual intake of dietary caffeine on single-dose kinetics of theophylline in healthy human subjects." Eur J Clin Pharmacol 44 (1993): 295-8

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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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