A dearth of data: the problem of phosphorus in prescription medications

Abstract

A high dietary intake of phosphorus is considered by most to be a significant health threat for dialysis patients. Efforts to include the phosphorus content of foods on the nutrition label in the US have, to date, been fruitless. Another source of phosphorus, largely unrecognized, is prescription medications. These may contain phosphorus as indicated on their package label; the amount is not quantified. We examined the labels of the branded forms of 200 of the most widely prescribed medications in Dialysis Clinic centers in the United States and found that 23 (11.5%) contained phosphorus. A sampling of different doses and manufacturers (generic and branded) of these drugs was analyzed for phosphorus content and found levels as high as 111.5 mg/dose (40 mg paroxetine). Notable were the phosphorus content of a generic 10 mg lisinopril (32.6 mg) and a generic 10 mg amlodipine (40.1 mg). The significant potential for iatrogenic injury accruing from the use of these drugs warrants efforts at remediation. Specific information on the phosphorus content of medications used by dialysis population needs to be made available to the dialysis community.

A Comparison of the Phosphorus Content in Prescription Medications for Hemodialysis Patients in Japan

“…If this above patient is also receiving a vitamin such as Renavite, the estimated absorbable phosphorus will be 25％ higher (90 mg). 10) Another way to consider the impact of this largely unrecognized source of dietary phosphorus is to consider it in terms of the number of phosphorus binding tablets required to block the absorption of an amount of dietary phosphorus equivalent to that in the phosphorus-containing drug. One tablet of sevelamer (800 mg) binds ～25.5 mg of phosphorus, whereas a cap-sule of calcium acetate (667 mg) binds ～28.5 mg. 10,16) Thus, simply to bind the phosphorus in the two tablets of paroxetine and amlodipine noted above, this unlucky patient would require additional doses of sevelamer or calcium acetate.…”

“…However, these data were limited to medications that are used in the United States. 10) Prescription medications frequently contain additives that are designed to the pharmaceutical quality of a drug, such as solubility, pH adjustment, stabilizers and absorption in Japan. However, the contents of these additives in prescription medications are frequently not available.…”

The extra-phosphate intestinal load from medications: is it a real concern?

“…The most prevalent form in the excipient mixture was calcium phosphate, which has a lower rate of intestinal absorption than sodium phosphate salts [9]. With respect to the published papers dealing with this argument, namely the studies of Sherman et al [7] and Sultana et al [8] which included only the medications prescribed to their two patient cohorts, in the present study we carried out a systematic screening of all medications potentially administered to CKD patients by oral route as long-term therapy, i.e. we examined all the medications existing in the considered ATC classes.…”

“…Sherman et al [7] recently examined the labels of 200 branded forms of the most prescribed medications in dialysis units in the United States and found that 11.5 % of them contained phosphorus. They measured the effective P content per tablet and found that it was as high as 111.5 mg for a dose of 40 mg paroxetine.…”

“…clonidine 0.2 mg, the phosphate content was negligible. No relationship was found between the type (brand or generic) or the active pharmaceutical ingredient (API) dosage and the amount of phosphate present as excipient [7]. Sultana et al examined the risk of assuming phosphate from medications in an Italian cohort of CKD patients [8].…”