Drug Interactions between Aralen Phosphate and i3odine Max

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.

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MONITOR: Excessive intake of dietary iodine (e.g., iodised salt) may interfere with adequate uptake of radioiodide by the thyroid .

MANAGEMENT: A diet low in iodine is recommended before initiating therapy with sodium iodide I-131 or I-123.

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ADJUST DOSING INTERVAL: Certain drugs may affect the pharmacokinetics, pharmacodynamics, and/or diagnostic results of radioiodides.

MANAGEMENT: Antithyroid agents such as carbimazole or propylthiouracil should generally be withheld for 1 week before administration of sodium iodide I-131 or I-123, and for a few days afterward. Salicylates, steroids, anticoagulants, antihistamines, antiparasitics, penicillins, sulfonamides, tolbutamide, thiopental, and nitroprusside should generally be withheld for 1 week. Amiodarone, lithium, and benzodiazepines should be withheld for at least 4 weeks.

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