Drug Interactions between iobenguane I 131 and Vilevev MB

MONITOR CLOSELY: The following interaction applies only to products containing sodium biphosphate that are used for bowel cleansing. It does not apply to products containing sodium biphosphate that are used for other, non-laxative related purposes.

Coadministration with agents that affect renal function or perfusion such as diuretics, ACE inhibitors, angiotensin receptor blockers, and nonsteroidal anti-inflammatory drugs (NSAIDs) may increase the risk of acute phosphate nephropathy associated with the use of bowel-cleansing phosphate solutions. The risk and/or severity of fluid and electrolyte disturbances may also be increased, which can lead to serious adverse events including cardiac arrhythmias, seizures, and renal impairment. Acute phosphate nephropathy is a rare adverse event that presents as acute renal failure with minimal proteinuria and a bland urine sediment. Renal biopsy findings are consistent with nephrocalcinosis and include acute and/or chronic renal tubular injury, calcium-phosphate crystal deposition in the distal tubules and collecting ducts, and no other pattern of histological injury. The risk of acute phosphate nephropathy stems from the large phosphate load, fluid shifts, and decreased intravascular volume, which can be exacerbated in the presence of medications that affect renal perfusion or function. In reported cases, acute renal failure was typically diagnosed within two to five months of colonoscopy. These cases often resulted in permanent impairment of renal function, some requiring long-term dialysis.

MANAGEMENT: Caution is advised when bowel-cleansing phosphate preparations are prescribed in patients treated with agents that affect renal function or perfusion, particularly if they are frail or elderly. Bowel-cleansing phosphate preparations should not be used in patients who have impaired renal function or perfusion, dehydration, or uncorrected electrolyte abnormalities. In patients at risk for acute phosphate nephropathy, baseline and postprocedure labs including serum electrolytes, calcium, phosphate, BUN, and creatinine should be performed. Patients should be advised not to exceed the recommended dosage of their bowel-cleansing preparation and to drink sufficient quantities of clear fluids during before, during, and after bowel cleansing. Limited data suggest that administration of an electrolyte rehydration solution may attenuate the electrolyte abnormalities and hypovolemia. Hospitalization and intravenous fluid hydration may be appropriate for frail or elderly patients who may be unable to drink an adequate volume of fluid.

GENERALLY AVOID: Coadministration with drugs that reduce catecholamine uptake or deplete catecholamine stores may interfere with iobenguane I-131 uptake into neuroendocrine tumors such as pheochromocytoma and paraganglioma that express high levels of norepinephrine transporter on their cell surfaces. Since iobenguane is similar in structure to norepinephrine and is subject to the same uptake and accumulation pathways as norepinephrine, drugs that alter norepinephrine disposition in adrenergic nerve terminals and presynaptic storage vesicles will likewise affect iobenguane. Dosimetry calculations and efficacy of iobenguane I-131 may be altered. These drugs include central nervous system stimulants (e.g., amphetamines, cocaine, methylphenidate); norepinephrine and dopamine reuptake inhibitors (e.g., phentermine); norepinephrine and serotonin reuptake inhibitors (e.g., tramadol); central monoamine depleting drugs (e.g., reserpine); nonselective beta-adrenergic blockers (e.g., labetalol); alpha agonists or alpha/beta agonists (e.g., pseudoephedrine, phenylephrine, ephedrine, phenylpropanolamine, naphazoline); monoamine oxidase inhibitors; tricyclic antidepressants; norepinephrine reuptake inhibitors (e.g., bupropion, duloxetine, mirtazapine, venlafaxine); and botanicals that may inhibit reuptake of norepinephrine, serotonin, or dopamine (e.g., ephedra, ma huang, St John's wort, yohimbine). These drugs were not permitted in clinical trials that assessed the safety and efficacy of iobenguane I-131.

MANAGEMENT: Drugs that reduce catecholamine uptake or deplete catecholamine stores should be discontinued for at least five biological half-lives before administration of either the dosimetry dose or a therapeutic dose of iobenguane I-131. Do not administer these drugs until at least 7 days after each iobenguane I-131 dose. Patients should be monitored for the occurrence of clinically significant withdrawal symptoms, especially patients with elevated levels of circulating catecholamines and their metabolites.