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Drug Interactions between Seroquel XR and st. john's wort

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

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Interactions between your drugs

Major

QUEtiapine St. John's wort

Applies to: Seroquel XR (quetiapine) and st. john's wort

ADJUST DOSE: Coadministration with potent inducers of CYP450 3A4 may significantly decrease the plasma concentrations of quetiapine, which is primarily metabolized by the isoenzyme. In 18 psychiatric patients receiving quetiapine 300 mg twice daily, addition of the potent CYP450 3A4 inducer carbamazepine (200 mg three times daily) decreased mean quetiapine peak plasma concentration (Cmax) and systemic exposure (AUC) by 80% and 87%, respectively, and increased oral clearance (Cl/F) by 7.5-fold compared to quetiapine administered alone. The interaction has also been reported with phenytoin, another potent CYP450 3A4 inducer. In ten subjects with various affective disorders, coadministration of quetiapine (250 mg orally three times a day) with phenytoin (100 mg orally three times a day) decreased the mean steady-state Cmax, trough plasma concentration (Cmin) and AUC of quetiapine by 66%, 89% and 80%, respectively. The mean oral clearance increased by 5.5-fold.

MANAGEMENT: Increased dosages of quetiapine may be required during chronic treatment (greater than 7 to 14 days) with potent CYP450 3A4 inducers. The manufacturer recommends an increase of up to 5-fold the original dosage of quetiapine. Further adjustments should be made based on clinical response and tolerance. The safety of dosages above 800 mg/day has not been established in clinical trials. Continued treatment at higher dosages should only be considered following careful consideration of risks and benefits. When the CYP450 3A4 inducer is discontinued, the dosage of quetiapine should be reduced to the original level within 7 to 14 days.

References

  1. (2001) "Product Information. Seroquel (quetiapine)." Astra-Zeneca Pharmaceuticals
  2. (1997) "Quetiapine for schizophrenia." Med Lett Drugs Ther, 39, p. 117-8
  3. Wong YWJ, Yeh C, Thyrum PT (2001) "The effects of concomitant phenytoin administration on the steady-state pharmacokinetics of quetiapine." J Clin Psychopharmacol, 21, p. 89-93
  4. Grimm SW, Richtand NM, Winter HR, Stams KR, Reele SB (2006) "Effects of cytochrome P450 3A modulators ketoconazole and carbamazepine on quetiapine pharmacokinetics." Br J Clin Pharmacol, 61, p. 58-69
  5. Cerner Multum, Inc. "Australian Product Information."
View all 5 references

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Drug and food interactions

Moderate

St. John's wort food

Applies to: st. john's wort

GENERALLY AVOID: An isolated case report suggests that foods containing large amounts of tyramine may precipitate a hypertensive crisis in patients treated with St. John's wort. The mechanism of interaction is unknown, as St. John's wort is not thought to possess monoamine oxidase (MAO) inhibiting activity at concentrations achieved in vivo. The case patient was a 41-year-old man who had been taking St. John's wort for seven days prior to presentation at the emergency room with confusion and disorientation. The patient recalled last eating aged cheese and having a glass of red wine approximately 10 hours prior to admission. No other cause of delirium or hypertension could be identified. In addition, alcohol may potentiate some of the pharmacologic effects of St. John's wort. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Until further information is available, patients treated with St. John's wort should consider avoiding consumption of protein foods in which aging or breakdown of protein is used to increase flavor. These foods include cheese (particularly strong, aged or processed cheeses), sour cream, wine (particularly red wine), champagne, beer, pickled herring, anchovies, caviar, shrimp paste, liver (particularly chicken liver), dry sausage, figs, raisins, bananas, avocados, chocolate, soy sauce, bean curd, yogurt, papaya products, meat tenderizers, fava beans, protein extracts, and dietary supplements. Caffeine may also precipitate hypertensive crisis so its intake should be minimized as well. Patients should also be advised to avoid or limit consumption of alcohol.

References

  1. Patel S, Robinson R, Burk M (2002) "Hypertensive crisis associated with St. John's Wort." Am J Med, 112, p. 507-8

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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.

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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