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Drug Interactions between cascara sagrada / magnesium hydroxide and Plaquenil

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

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Interactions between your drugs

Moderate

hydroxychloroquine magnesium hydroxide

Applies to: Plaquenil (hydroxychloroquine) and cascara sagrada / magnesium hydroxide

ADJUST DOSING INTERVAL: Concomitant administration of antacids or kaolin may reduce the oral bioavailability of chloroquine. The proposed mechanism is adsorption of chloroquine by polyvalent cations present in these agents. Delayed dissolution of chloroquine tablets in the presence of antacids may also be a contributing factor. In six healthy study subjects, administration of a single 1 gram dose of chloroquine phosphate in combination with a 1 gram dose of magnesium trisilicate or kaolin decreased chloroquine systemic exposure (AUC) by approximately 18% and 29%, respectively, compared to administration alone. In vitro evidence of the interaction has also been reported for other antacids including calcium carbonate and gerdiga. The clinical significance has not been established.

MANAGEMENT: Chloroquine product labeling suggests separating the doses by at least 4 hours if concomitant therapy with antacids or kaolin is required. The same precaution may be applicable to hydroxychloroquine, although no data are available to support this recommendation. Some authorities recommend separating the dose of hydroxychloroquine from antacids and kaolin by at least 2 hours (AU).

References

  1. D'Arcy PF, McElnay JC (1987) "Drug-antacid interactions: assessment of clinical importance." Drug Intell Clin Pharm, 21, p. 607-17
  2. (2002) "Product Information. Aralen (chloroquine)." Sanofi Winthrop Pharmaceuticals
  3. McElnay JC, Mukhtar HA, Arcy PF, Temple DJ (1982) "In vitro experiments on chloroquine and pyrimethamine absorption in the presence of antacid constituents or kaolin." J Trop Med Hyg, 85, p. 153-8
  4. McElnay JC, Mukhtar HA, D'Arcy PF, Temple DJ, Collier PS (1982) "The effect of magnesium trisilicate and kaolin on the in vivo absorption of chloroquine." J Trop Med Hyg, 85, p. 159-63
  5. Wallace AW, Amsden GW (2002) "Is it really OK to take this with food? Old interactions with a new twist." J Clin Pharmacol, 42, p. 437-43
  6. Iwuagwu MA, Aloko KS (1992) "Adsorption of paracetamol and chloroquine phosphate by some antacids." J Pharm Pharmacol, 44, p. 655-8
  7. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  8. Cerner Multum, Inc. "Australian Product Information."
View all 8 references

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Moderate

hydroxychloroquine cascara sagrada

Applies to: Plaquenil (hydroxychloroquine) and cascara sagrada / magnesium hydroxide

MONITOR: Bowel cleansing as well as overuse of certain laxatives may cause electrolyte loss and increase the risk of torsade de pointes ventricular arrhythmia in patients treated with drugs that prolong the QT interval. Electrolyte disturbances including hypokalemia and hypomagnesemia have been reported with laxative abuse and are known risk factors for torsade de pointes associated with QT interval prolongation.

MANAGEMENT: Patients treated with drugs that prolong the QT interval should exercise caution when self-medicating with laxatives. The recommended dosage and duration of use should not be exceeded. Patients treated with lactulose for more than six months should be monitored periodically for electrolyte imbalance. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.

References

  1. Chin RL (1998) "Laxative-induced hypokalemia." Ann Emerg Med, 32, p. 517-8
  2. Muller-Lissner SA (1993) "Adverse effects of laxatives: fact and fiction." Pharmacology, 47, p. 138-45
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  4. Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
  5. Cerner Multum, Inc. "Australian Product Information."
  6. Schaefer DC, Cheskin LJ (1998) "Constipation in the elderly." Am Fam Physician, 58, p. 907-14
View all 6 references

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Drug and food interactions

Moderate

hydroxychloroquine food

Applies to: Plaquenil (hydroxychloroquine)

GENERALLY AVOID: Theoretically, grapefruit and grapefruit juice may increase the plasma concentrations of hydroxychloroquine or chloroquine and the risk of toxicities such as QT interval prolongation and ventricular arrhythmias. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruit. Following coadministration with cimetidine, a weak to moderate CYP450 3A4 inhibitor, a 2-fold increase in chloroquine exposure occurred. Since chloroquine and hydroxychloroquine have similar structures and metabolic elimination pathways, a similar interaction may be observed with hydroxychloroquine. 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. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Although clinical data are lacking, it may be advisable to avoid the consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract during hydroxychloroquine or chloroquine therapy.

References

  1. Cerner Multum, Inc. "Australian Product Information."

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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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