The dangers of oral sodium phosphate preparations are fairly well known in the medical community. In 2006 the FDA issued it’s first warning that patients taking oral sodium phosphate preparations are at risk for potential for acute kidney injury. Two years later, over-the-counter preparations of these drugs were voluntarily withdrawn by the manufacturers. Those agents still available by prescription were given black box warnings mainly due to acute phosphate nephropathy that can result in renal failure, especially in older adults. Despite all this talk of oral preparations, little was mentioned about a sodium phosphate preparation that is still available over-the-counter – the Fleet enema.
Why Oral Sodium Phosphate Preparations Are Dangerous
Before we go into the risks of Fleet enemas, lets spend just a couple sentences on why oral sodium phosphate preparations carry significant risks. First, oral sodium phosphate preparations can cause significant fluid shifts within the colon resulting in intravascular volume depletion. Second, these preparations can cause electrolyte disturbances including significant hyperphosphatemia, hypocalcemia, and hypokalemia. A significant clinically important rise in serum phosphate can even be seen in elderly patients with normal renal function. (J Gastroenterol Hepatol. 2004;19(1):68). Lastly, phosphate nephropathy may occur due to the transient and potentially severe increase in serum phosphate combined with volume depletion from the fluid shifts.
Why the Same Holds True for Sodium Phosphate Enemas (aka Fleet enemas)
A fleet enema works as a hyper-osmotic laxative that draws in water into the gastrointestinal tract. In healthy younger adults, this action shouldn't pose a problem as the laxative action from a fleet enema occurs relatively quickly, so there is little absorption of phosphate.
However, what if your patient isn't a health young adult? What if they are older, frailer, and taking multiple medications, including some that may slow their bowels down like opioids or those with anticholinergics properties? A recent publication by Yaacov Ori and colleagues titled "Fatalities and Severe Metabolic Disorders Associated With the Use of Sodium Phosphate Enemas" gives some evidence that great caution is warranted when prescribing Fleet enemas in this population.
Yaacov Ori and colleauges conducted a retrospective case series of 11 elderly patients (mean age of 80) at the Rabin Medical Center in Israel. Ten of these patients received Fleet enemas for relief of constipation and one received it as a proctoscopy prep. Three of these patients received 500-800 mL of sodium phosphate and 8 patients received approximately 250mL (for a comparison, a typical over-the-counter Fleet enema comes in either a 118 and 197 ml dose). Baseline renal function was normal (eGFR by MDRD of 60mL/min) in 4 patients with a range of 25 to 57 mL/min in the other seven.
What they found was that renal function deteriorated in all 11 patients. Hypotension and extreme hyperphosphatemia was prominent in 8 of these patients. The serum calcium level was dangerously low in 8 patients. Five patients died. An autopsy on one patient revealed calcium phosphate calcifications within the renal tubular lumens.
The Take Home Point - Just Don't Use It
There are some medications that despite years of use should be clearly abandoned in older individuals or those with advanced illness (i.e. the GeriPal population). Colace is an excellent example of a medication that offers little benefit but also little harm in younger, healthier populations. However, in patients that are frail, hospitalized, or approaching the end of life, the risks begin to significantly outweigh any possible benefit.
Fleet enemas should also be relegated to this list of medications that should generally be avoided unless your patient is a very robust older adult. We should also teach others that if you do happen to order a Fleet enema for a hospitalized or nursing home patient, you should never give a second dose in succession if the first trial fails. Lastly, we should educate patients and their caregivers that medications, like the pictured Fleet product with "70% more volume," should not be considered safe just because it can be found in the over-the-counter aisle.
by: Eric Widera (follow on twitter at @ewidera)