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Depakote ER - easy to confuse with Depakote (delayed release)  

From the February 7, 2001 issue

PROBLEM: Abbott recently marketed DEPAKOTE ER, a new tablet formulation of extended release divalproex sodium intended for migraine sufferers. This product has a polymer matrix delivery system that sustains the release of divalproex sodium steadily over 18 to 24 hours. The dosing interval for this new formulation should not be more frequent than once daily (q 24 h). Hypotension, sedation, heart block, or deep coma may occur if Depakote ER is confused with DEPAKOTE delayed release tablets, a formulation that is enteric coated, released over an 8 to 12 hour period, and can be taken more than once daily.

Depakote (delayed release) is indicated for patients with mania associated with bipolar disorder or for certain forms of epilepsy. However, like Depakote ER, it is also indicated for migraine headaches. Confusion is quite possible because the brand names are so similar, both are available in a 500 mg tablet strength, and the terms “delayed release” and “extended release” are not sufficient to adequately differentiate the products.

The two formulations are not substitutable. Although both divalproex sodium formulations are sustained release, only the Depakote ER should be dosed once daily. Quite a few practitioners have reported the high potential for confusion between these two sustained release formulations, and we’ve already received one report about an actual error where the patient received 1,500 mg of Depakote (delayed release) instead of Depakote ER. The patient developed significant hypotension and sedation about 9 hours later as the full dose was released more rapidly than with the extended release formulation. Fortunately this patient experienced no further adverse effects and no additional treatment was necessary.

SAFE PRACTICE RECOMMENDATION: Educate staff about the different dosing schedules and indications for both formulations of divalproex sodium. If possible, initiate a computerized alert to remind staff about the potential for mix-ups and design computer mnemonics to decrease the likelihood that the drugs will appear on the computer screen simultaneously. Also, be wary of verbal orders since “ER” could sound like “DR,” which some have used unofficially to designate the delayed release product. When repeating back the order to the prescriber, the clinician should always use the full words “extended release” or “delayed release,” not abbreviations. The letters “EC,” used by some to describe the enteric coated product, could also be confused with “ER.”

When either drug is prescribed, determine its indication for use. Depakote ER is indicated for the prophylaxis of migraine headaches. Unlike Depakote (delayed release), Depakote ER has not been evaluated in the treatment of mania or epilepsy. Separate the storage of the drug containers and use auxiliary warning labels to differentiate the products. In hospital settings, avoid having both forms available if possible. Educate patients regarding the potential for confusion between these two formulations. Abbott should consider changing the name for the extended release product. In the end, a standard way of designating various sustained release forms of drugs is needed

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