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Drug Interactions between sildenafil and tacrolimus

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

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Interactions between your drugs

Moderate

tacrolimus sildenafil

Applies to: tacrolimus and sildenafil

ADJUST DOSE: Coadministration with tacrolimus may increase the plasma concentrations of sildenafil and its active metabolite due to competitive inhibition of CYP450 3A4 metabolism by tacrolimus. In a study of ten male kidney transplant patients receiving immunosuppressive therapy containing tacrolimus, administration of a 50 mg dose of sildenafil produced peak plasma drug concentrations (Cmax) and area under the concentration-time curve (AUC) that were 44% and 90% greater, respectively, compared to historical data for healthy volunteers provided by the manufacturer. The elimination half-life was also prolonged (4.7 hours vs. 3 hours). The AUC of the active metabolite was 2.8-fold greater than in historical controls, and elimination half-life was 8.6 hours (vs. 3.5 hours). Pronounced decreases in blood pressure were also observed, which were much more intense and longer lasting than those reported in historical controls following ingestion of a 100 mg sildenafil dose. Sildenafil appears to have no significant effect on the pharmacokinetics of tacrolimus.

MANAGEMENT: A starting dose of 25 mg sildenafil may be appropriate during concomitant therapy with tacrolimus. Patients should be advised to promptly notify their physician if they experience severe adverse effects of sildenafil such as pain or tightness in the chest or jaw, irregular heartbeat, nausea, shortness of breath, visual disturbances, syncope, or prolonged erection (greater than 4 hours).

References

  1. Christ B, Brockmeier D, Hauck EW, Friemann S "Interactions of sildenafil and tacrolimus in men with erectile dysfunction after kidney transplantation." Urology 58 (2001): 589-93

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Drug and food interactions

Moderate

tacrolimus food

Applies to: tacrolimus

ADJUST DOSING INTERVAL: Consumption of food has led to a 27% decrease in the bioavailability of orally administered tacrolimus.

MANAGEMENT: Tacrolimus should be administered at least one hour before or two hours after meals.

GENERALLY AVOID: Grapefruit juice has been reported to increase tacrolimus trough concentrations. Data are limited, but inhibition of the CYP450 enzyme system appears to be involved.

MANAGEMENT: The clinician may want to recommend that the patient avoid ingesting large amounts of grapefruit juice while taking tacrolimus.

References

  1. "Product Information. Prograf (tacrolimus)." Fujisawa PROD (2001):
  2. Hooks MA "Tacrolimus, a new immunosuppressant--a review of the literature." Ann Pharmacother 28 (1994): 501-11

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Moderate

sildenafil food

Applies to: sildenafil

GENERALLY AVOID: Coadministration with grapefruit juice may slightly increase the oral bioavailability and delay the onset of action of sildenafil. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In a randomized, crossover study with 24 healthy male volunteers, ingestion of 250 mL of grapefruit juice one hour before and concurrently with a 50 mg dose of sildenafil increased the mean area under the plasma concentration-time curve (AUC) of sildenafil and its pharmacologically active N-desmethyl metabolite by 23% and 24%, respectively, compared to water. Peak plasma concentrations (Cmax) were unaltered, but the time to reach sildenafil Cmax was prolonged by 0.25 hour. The observed increase in sildenafil bioavailability is unlikely to be of clinical significance in most individuals. However, pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability and may be significant in the occasional susceptible patient. Indeed, one subject in the study had a 2.6-fold increase in sildenafil concentrations.

MANAGEMENT: It may be advisable to avoid administration of sildenafil with grapefruit juice to prevent potential toxicity and delay in onset of action.

References

  1. Jetter A, Kinzig-Schippers M, Walchner-Bonjean M, et al. "Effects of grapefruit juice on the pharmacokinetics of sildenafil." Clin Pharmacol Ther 71 (2002): 21-29

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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

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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