Petition Urges FDA To Take Oral Sodium Phosphate Laxatives Off OTC Market

FDA should switch oral sodium phosphate bowel cleansers from over-the-counter to prescription status due to safety concerns or take them off the market altogether, according to a Sept. 20 citizen petition.

Natasha Leskovsek, attorney with D.C.-based firm HellerEhrman, filed a citizen petition on behalf of an anonymous client to withdraw the commercial marketing authorization for OSP products due to potential risks of renal failure caused by nephrocalcinosis. Alternatively, Leskovsek requests the agency add a black box warning and reclassify OSP products as Rx-only.

The petition says, "Physiologically, the use of OSP as a purgative agent is associated with a transient rise in serum phosphate level and consequent reduction in serum calcium. In some patients active renal tubular excretion mechanisms may be unable to deal with the excess phosphate load."

It has become increasingly clear that OSP use "presents an avoidable and potentially catastrophic risk of renal failure to some patients and that screening for known risk factors cannot identify all potentially affected patients," Leskovsek writes in the petition.

"Since OSP products are used in a colonoscopy screening context in otherwise healthy populations, and because equally effective and safer alternatives for bowel preparation exist, the withdrawal of commercial authorization for OSP products is warranted," she writes.

The "smallest logical step" for FDA to take would be to "make all of these products Rx to which we would like to see a black box warning added," Leskovsek told "The Tan Sheet" in an e-mail. "It is unclear whether making the one OTC product Rx would have detriment on the capacity for self-care, since the procedure for which it is used (colonoscopy) is obviously physician guided and prescribed."

Currently, C.B. Fleet's Phospho-soda is the only OTC OSP product on the market, but in August the firm removed the "bowel cleanser" indication from its packaging following several lawsuits (¹ 'The Tan Sheet' Aug. 13, 2007, In Brief).

If FDA agrees with the citizen petition that renal complication rate is higher than the agency previously estimated it "tips the risk/benefit to a need for a change," Leskovsek says.

Since the reports to MedWatch regarding safety issues surrounding OSP products have increased, "One conclusion is that the rate of this complication was previously underestimated and may be why they thought it safe to leave the OTC product alone," Leskovsek said in her e-mail.

FDA may view the increased reporting as no change from the baseline rate, "just better reporting since physicians now make the connection between nephrocalcinosis and OSP use," she adds.

However, Leskovsek says if FDA states it continues to believe the risk/benefit profile for OSP products supports OSP availability both on an Rx and OTC basis and without a black box warning then, "Physicians prescribing both categories of product likely enjoy better peace of mind in prescribing or recommending OTC OSPs and companies marketing these products potentially face less product liability."

Leskovsek said her client's "incentive was only to have the agency actively revisit the basis for their decision in responding to prior petitions and issuing earlier advice to physicians, to ensure that the agency takes note of interim MedWatch data on OSP-induced nephrocalcinosis."

Previous citizen petitions have requested FDA make OSP products prescription only. In 2000, Braintree Labs, marketer of Rx gastrointestinal lavage preparations GoLytely and NuLytely, requested similar action (² (Also see "Professional Labeling For OTC Sodium Phosphates Laxatives Requested" - Pink Sheet, 4 Aug, 2003.), p. 12).

FDA denied the previous petition in 2001 on the grounds the "then-proposed limitations on container size were sufficient, as the majority of renal problems reported in the literature reflected clinicians' failure to observe dosage guidelines," the current petition says.

While FDA denied Braintree Labs' petition in 2001, the agency is aware of renal complications associated with OSP products and in fact issued a safety alert in May 2006 (³ (Also see "FDA MedWatch Links Fleet’s Sodium Phosphate Products To Kidney Disorder" - Pink Sheet, 15 May, 2006.), p. 10).

- Rebekah Moan