Cases & Commentaries

Citrate Mix-Up

Commentary By Robert J. Weber, MS, RPh

The Case

A 36-year-old woman with multiple sclerosis,
diabetes, and chronic renal failure was transferred from a skilled
nursing facility (SNF) to the hospital for treatment of an
infection. On admission, an order was written for Bicitra, 30 mL
four times daily—a medication that she had been receiving in
the SNF. The hospital pharmacist filled the order with Polycitra
instead of Bicitra, and dispensed a 473-mL container. (Polycitra is
a combination product containing citric acid and potassium citrate;
Bicitra contains only citric acid.) Assuming the Polycitra was
dispensed in the appropriate quantity for a single dose, the nurse
gave the patient the bottle and a straw and instructed her to drink
the entire amount.

When the nurse on the next shift noticed the
empty container with the straw, she interviewed the patient. The
patient confirmed that she consumed the entire amount and said that
it tasted good. The physician was notified. A STAT serum potassium
level was >8 mEq/L (normal 3.5-5), and her blood glucose was 600
mg/dL (normal

The patient was treated with Kayexalate (sodium
polystyrene sulfonate) and an insulin infusion, and she recovered
within 24 hours without further complications.

The Commentary

This is a case of hyperkalemia and hyperglycemia
from mistaken administration and overdosage of Polycitra (potassium
citrate/citric acid/sodium citrate), which was substituted for
Bicitra (citric acid/sodium citrate). These medications are both
used as urinary alkalinizing agents for the prevention of urinary
stones. Polycitra is also used in patients requiring potassium
replacement or with a restricted sodium intake.

This error led to increased patient monitoring
and drug treatment to normalize the serum potassium and glucose. In
spite of the patient's pre-existing renal disease and diabetes, no
permanent harm resulted; the outcome of this error could have been
more serious. For example, the Institute for Safe Medication
Practices (ISMP) reported a case of a 15-month-old child with renal
disease who received Polycitra instead of Bicitra for 12 days,
resulting in a 7-day hospital admission for hyperkalemia.(1)
Potassium levels in the range of 7 to 8 can easily be fatal.

MEDMARX, the United States Pharmacopeia (USP)
medication error reporting system, received 187 medication error
reports involving Polycitra and Bicitra from 2002 to
2005.(2) The
errors include wrong dosage, dosage strength confusions (ordered as
mg instead of mL or mEq instead of mL), not diluting the solution
prior to administration, missed administrations prior to surgery,
mix-up between mineral oil and Bicitra, and Polycitra-K
administered instead of Polycitra, resulting in a two-fold increase
in potassium citrate compared to Polycitra. Among those reports,
four medication errors (2.1%) involving either Polycitra or Bicitra
resulted in patient harm.

This case raises four questions: How did the
“sound-alike” proprietary names of these two
medications contribute to the error? What strategies can be used to
minimize medication mistakes when similar products have important
differences? How can organizations establish drug storage,
packaging, and dispensing practices to prevent medication
administration errors? What systems are available to the nurse and
others who administer medications to recognize acceptable dosing
forms?

This case illustrates the potential hazards
associated with sound-alike drug names. Most likely, the similar
sounding names of the two medications (Bicitra and
Polycitra) caused the pharmacist to interpret these agents
as generic equivalents of one another, when in fact they are not.
Review and action to prevent errors involving sound-alike (and
look-alike) drugs is a Joint Commission on Accreditation of
Healthcare Organizations (JCAHO) National Patient Safety Goal. Many
sound-alike/look-alike medication errors involve drugs used for
different indications (eg, Zantac and Xanax). Although this was not
the case here, the erroneous substitution was serious.

Thoughtful speculation on the reasons that this,
or any other, pharmacist failed to recognize the differences in
these medications can help inform the implementation of effective
error-prevention systems. Most likely, the pharmacist assumed that
all citric acid products are the same. In fact, Micromedex
identifies at least five citric acid/citrate products in various
combinations and strengths, lending to the general confusion around
these products.

An effective method for preventing the wrong
selection of a citric acid product is to limit the stocking of
citric acid to a single product in any given pharmacy. For example,
Bicitra might be selected because this agent is more commonly used
than the potassium-containing citrate solutions. The formulary
review process of the Pharmacy and Therapeutics Committee can be a
forum to discuss limiting the stocking of these medications, as
this committee can weigh the indications for each product with
input from potential prescribers. This committee may also develop
prescribing guidelines for the use of urinary alkalinizing
agents.

When more than one citric acid product is
stocked, alerts can be placed in the medication order entry system
that warn the physicians, pharmacists, and other staff of the
differences between and specific indications for these two
products. Reminder notes on medication labels may also be used to
alert staff to the differences between these products (eg, labeling
Polycitra with a phrase “Do not confuse with Bicitra,”
and vice versa for Bicitra). Finally, the order entry system
may be tailored to screen the patient's laboratory values (serum
potassium) and disease states (renal failure, as indicated by serum
creatinine value) when Polycitra is electronically ordered.

Medication
reconciliation (also a 2006 National Patient Safety Goal) is a
process that involves a review of a patient's medication orders and
adjustment of the regimen based on the patient's level of care and
medication needs.(3) In
this case, medication reconciliation may have alerted the nurse or
pharmacist to the indication for and dosage of Bicitra, along with
the potential differences in the citric acid products. The nurse
may have recognized a problem when Polycitra was dispensed to the
patient and may have appreciated the large disparity between the
apparent dose (mistakenly interpreted as an entire 473-mL
container) and the patient's previous dose (likely 30 mL).

The Polycitra dosage error might also have been
prevented had the pharmacy packaged the Polycitra in unit-dose
containers prior to dispensing. Supplying the product as a
unit-of-use dose would have prevented the administration of such a
large volume. Citrate products also require dilution prior to
administering to prevent stomach upset; placing a “Must be
diluted prior to administration” label on the 473-mL bottle
may have prompted the nurse to further check the administration
instructions (eg, dosage). Importantly, to avoid any mistakes, bulk
containers of medications (eg, larger bottles of liquid or oral
medications) should never be dispensed for individual patient
use.

Bar code medication administration screening
technology (BCMA) may have prevented this Polycitra overdosage,
because these systems compare a drug's bar code to the electronic
medication order, alerting the nurse of a potential
error.(4) The
bar code for a unit-dose (or unit of use, eg, a 30-mL unit-dose
package) product of Polycitra would likely be different than the
bar code of the Polycitra bulk bottle of 16 ounces. Accordingly,
BCMA would have at least provided a warning to the nurse that the
product volume was incorrect.

The nurse in this case provided the patient with
the entire bottle of Polycitra, thinking it was a single-dose
administration. All medication dispensed and stored on nursing
units and areas outside the pharmacy must be packaged as
unit-of-use doses. Most BCMA systems require that all products are
packaged and bar coded by unit of use; BCMA may have prevented this
error by forcing a smaller dose of Polycitra to be
administered.

Take-Home Points

  • Confusing Bicitra and Polycitra or not
    appreciating their important differences may cause adverse drug
    events.
  • Establishing a system of labeling,
    computer alerts, and information sheets warns professionals of the
    differences in these products even though they “sound
    alike.”
  • Limiting the stocking of citric acid
    products to one or two most commonly used products can help to
    reduce confusion.
  • Bulk quantities of medications should be
    repackaged into unit-of-use containers before they are
    dispensed.
  • Bar code technology can alert
    pharmacists and nurses of discrepancies between the product or
    dosage ordered and that which is dispensed or administered.
  • The hospital's Pharmacy and Therapeutics
    Committee can develop prescribing guidelines for using these
    citrate agents that inform staff of their differences and suggest
    therapeutic alternatives.

Robert J. Weber MS, RPh
Associate Professor and Chair
University of Pittsburgh School of Pharmacy
Department of Pharmacy and Therapeutics
Executive Director of Pharmacy
University of Pittsburgh Medical Center

References

1. Mix-up between BICITRA (sodium citrate/citric
acid) and POLYCITRA (sodium citrate/citric acid/potassium citrate).
ISMP Medication Safety Alert! Community/Ambulatory Care Edition.
October 2005.

2. MEDMARX [database online]. Rockville, MD:
United States Pharmacopeia. Available at: https://www.medmarx.com/. Accessed March 28,
2006.

3. Pronovost P, Weast B, Schwarz M, et al.
Medication reconciliation: a practical tool to reduce the risk of
medication errors. J Crit Care. 2003;18:201-205.
[go to PubMed]

4. Neuenschwander M, Cohen MR, Vaida AJ, Patchett
JA, Kelly J, Trohimovich B. Practical guide to bar coding for
patient medication safety. Am J Health-Syst Pharm. 2003;60:768-779.
[go to PubMed]