Drug Interactions between propafenone and Uro-Phosphate

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of propafenone. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. In over 90% of patients, propafenone is rapidly and extensively converted to 2 active metabolites: 5-hydroxypropafenone via CYP450 2D6 and N-depropylpropafenone (norpropafenone) via CYP450 3A4 and 1A2. In less than 10% of patients (approximately 6% of Caucasians in the U.S. population), however, metabolism of propafenone is slower because the 5-hydroxy metabolite is not formed, or minimally formed, due to a genetic deficiency in CYP450 2D6. In these poor metabolizers of CYP450 2D6, clearance of propafenone via the CYP450 3A4 and 1A2 metabolic pathways becomes more important, and inhibition of these pathways may substantially increase systemic exposure to propafenone. Likewise, patients taking concomitant inhibitors of CYP450 2D6 and 3A4 may experience similar pharmacokinetic effects. 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. Increased systemic exposure to propafenone may result in proarrhythmic events and exaggerated beta-adrenergic blocking activity.

MANAGEMENT: It may be advisable for patients to avoid the consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with propafenone.

Oral medications may not be properly absorbed when they are taken within one hour before starting sodium biphosphate for bowel cleansing. Talk to your doctor or pharmacist to see if you should adjust the dosing schedule of your other medications before you begin bowel cleansing treatment. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

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