Drug Interactions between Digitek and UroAv-B

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.

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MONITOR: Nonsteroidal anti-inflammatory drugs (NSAIDs) may increase plasma digoxin concentrations and half-life. The exact mechanism is unknown, but may be related to reduced renal clearance of digoxin. Data have been conflicting. The interaction has been reported with indomethacin and ibuprofen, but data for other NSAIDs are not available.

MANAGEMENT: Patients who require concomitant therapy should be monitored for altered pharmacologic effects of digoxin and for increased plasma levels. The digoxin dosage may require adjustment. Patients should be advised to notify their physician if they experience nausea, anorexia, visual changes, slow pulse, or irregular heartbeats.

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Anticholinergic agents may increase the absorption and oral bioavailability of some digoxin formulations. The proposed mechanism involves increased gastrointestinal transit time due to reduction of stomach and intestinal motility by anticholinergic agents. In one study, coadministration with propantheline (15 mg three times a day for 10 days) led to a 30% mean increase in serum digoxin levels in 9 of 13 elderly women receiving a slow-dissolution formulation of digoxin. The interaction has also been reported with formulations containing large particle size digoxin. Other studies have found no significant effect of propantheline on digoxin elixir, solution in capsules, rapid-dissolution tablets, and micronized digoxin tablets. Therefore, the interaction is not expected to occur with most digoxin products used today in industrialized countries (e.g., Lanoxin). Due to the drug's narrow therapeutic index, however, clinicians may consider monitoring patients more closely for digoxin side effects and toxicity during coadministration with anticholinergic agents. Patients should be advised to notify their physician if they experience potential signs and symptoms of digoxin toxicity such as nausea, anorexia, visual disturbances, slow pulse, and irregular heartbeats.

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