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Drug Interactions between Baycadron and Tenex

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

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Interactions between your drugs

Major

dexAMETHasone guanFACINE

Applies to: Baycadron (dexamethasone) and Tenex (guanfacine)

ADJUST DOSE: Coadministration with inducers of CYP450 3A4 may significantly decrease the plasma concentrations of guanfacine, which is primarily metabolized by the isoenzyme. Rifampin, a potent CYP450 3A4 inducer, has been reported to decrease guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) by 54% and 70%, respectively. A computer simulation suggests that efavirenz, a moderate CYP450 3A4 inducer, would reduce guanfacine Cmax and AUC by a similar magnitude.

MANAGEMENT: Close monitoring and dosage adjustment should be considered when guanfacine is administered with potent and moderate CYP450 3A4 inducers. For extended-release guanfacine, some manufacturers recommend increasing the dosage up to double the recommended level when initiating therapy in patients who are already receiving a CYP450 3A4 inducer. Further dosage adjustments may be required based on patient tolerance and response. If a CYP450 3A4 inducer is added to existing guanfacine therapy, the guanfacine dosage may be increased up to double the recommended level over 1 to 2 weeks. The dosage should be decreased to the recommended level over 1 to 2 weeks following discontinuation of the CYP450 3A4 inducer.

References

  1. Kiechel JR, Lavene D, Guerret M, Comoy E, Godin M, Fillastre JP "Pharmacokinetic aspects of guanfacine withdrawal syndrome in a hypertensive patient with chronic renal failure." Eur J Clin Pharmacol 25 (1983): 463-6
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. "Product Information. Intuniv (guanfacine)." Shire US Inc (2009):

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Drug and food interactions

Major

guanFACINE food

Applies to: Tenex (guanfacine)

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of guanfacine. The risk of adverse reactions such as hypotension, bradycardia, and sedation may increase. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Ketoconazole, a potent CYP450 3A4 inhibitor, has been reported to increase guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 2- and 3-fold, respectively. A computer simulation suggests that fluconazole, a moderate CYP450 3A4 inhibitor, would increase guanfacine Cmax and AUC by about 1.5- and 2-fold, respectively. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition.

GENERALLY AVOID: Alcohol may enhance the sedative and hypotensive effects of guanfacine.

GENERALLY AVOID: Administration of extended-release guanfacine with a high-fat meal may increase the bioavailability of guanfacine. When a single 4 mg dose of extended-release guanfacine was administered to adult volunteers with a high-fat breakfast, mean guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 75% and 40%, respectively, compared to dosing in a fasted state.

MANAGEMENT: Patients treated with guanfacine should avoid consumption of grapefruit and grapefruit juice. In addition, it is preferable to avoid or limit the use of alcohol during treatment. Patients should be advised against driving or operating hazardous machinery until they know how the medication affects them. The extended-release formulation of guanfacine should not be taken together with a high-fat meal.

References

  1. "Product Information. Tenex (guanfacine)." Wyeth-Ayerst Laboratories PROD (2001):
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. "Product Information. Intuniv (guanfacine)." Shire US Inc (2009):

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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.

See also

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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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