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Practitioners' Reporting News
Dispensing Errors with Depakote®:
New Formulation Creates Confusion.
Issued March 3, 2001
Eight medication error reports were recently submitted to the USP Medication
Errors Reporting Program (MER) involving the products Depakote® and
Depakote® ER. Both products contain the active ingredient divalproex
sodium and are available in 500-mg strengths. The products, however, differ
in their approved indications, and in their mechanisms of release.
In August 2000, the Food and Drug Administration approved Depakote ER for
prophylaxis of migraine headaches in adults. Depakote ER is not indicated
for the treatment of acute migraine headaches, nor has it been evaluated
for treatment of mania or epilepsy. Depakote, however, is indicated for the
treatment of manic episodes of bipolar disorders, epilepsy, and prophylaxis
of migraine headaches.
Depakote ER is an extended release tablet intended for once-a-day administration.
Extended-release tablets are formulated in such manner as to make the contained
medicament available over an extended period following ingestion. Expressions
such as "prolonged-action" and "sustained-release" have been used to describe
such dosage forms, however, the term "extended-release" is the term used
for "official" Pharmacopeial purposes.
On the other hand, Depakote is an enteric-coated tablet. Where the drug may
be destroyed or inactivated by the gastric acids or where it may irritate
the gastric mucosa, the use of "enteric" coatings is indicated. Such coatings
are intended to delay the release of the medication until the tablet has
passed through the stomach. The term "delayed-release" is used to describe
these types of formulations. Depakote is usually administered in divided
daily doses, either twice a day or three times a day. Thus if the products
are inadvertently interchanged, a patient could potentially receive an
unintentionally large dose all at once. Both formulations should be swallowed
whole, and should not be crushed or chewed.
Of the eight reports received:
- Three reports cited the names of the two products as confusing and
potentially contributing to the wrong formulation being dispensed.
- Five actual errors involving these products occurred because the
pharmacists were not aware that Depakote ER was available.
- In one case, a patient who was maintained on Depakote ER was being
admitted to the hospital. On the patient's hospital admission orders, the
nurse recorded that the patient was taking "DEPAKOTE XR 1500 mg PO qAM."
Possibly, "XR" was used as an abbreviation for "extended release." The hospital did not have the Depakote ER on the formulary. In the pharmacy's information system, the generic description of Depakote included the designation "ER" possibly indicating that the product was a "delayed release" formulation. Consequently, the pharmacist selected and dispensed Depakote 1500 mg. The patient became sedated and experienced a drop in blood pressure. Fortunately, the patient did not require treatment.
- Three patients, who received Depakote when Depakote ER was prescribed,
did not experience adverse outcomes.
- One error was intercepted before the wrong medication reached the
patient.
To prevent additional errors, it is recommended that alerts be posted indicating that two formulations of this product exist and that the prescriber be contacted if there is any question as to which formulation was intended.
Readers are advised that official USP cautions and warnings for drugs appear in the USP–NF or USP DI. Unless otherwise indicated, any advice or opinions expressed herein reflect solely the judgment of USP staff. Such statements are intended for further consideration and evaluation and may or may not be applicable to a particular practice. The USP Medication Errors Reporting Program is presented in cooperation with the Institute for Safe Medication Practices.
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