Abstracts

Drug intoxication after inadvertent substitution of an immediate-release drug with an extended-release formulation has been documented ([italic]Am J Health-Syst Pharm 2001;58:402-5).[/italic] Similarly, it has been speculated that clinical consequences could occur from a lack of recogntion of the differential biopharmaceutic characteristics of the divalproex sodium extended-release formulation (ER) versus the conventional delayed-release, enteric-coated formulation (EC) [italic](Ann Pharmacotherapy 2006; 40:619-25[/italic][italic]). [/italic]ER is approved for once daily administration, whereas EC is approved for multiple-daily dosing. We analyzed prospectively collected cases of adverse effects and breakthrough sizures in patients with epilepsy resulting from the unintentional substitution of EC for multiple-daily dosing due to medication dispensing errors., EC vs. ER dispensing errors were tabulated in epilepsy clinics between July 2001 and May 2006. Patients and caregivers were interviewed to determine pharmacy location, circumstances of error, and any seizures or adverse effects that followed the errors., Substitution of clinican prescribed once-daily ER with EC occurred in six cases, due to lack of availability of ER at the local pharmacy at the time of prescription submission, and in five cases due to mistakes on refills of a previous correctly filled prescription. Two experienced increased tremor of mild but noticeable severity. Three patients had breakthrough seizures. Side effects and seizures abated after discovery of the errors and the correct ER dosing regimens were resumed. One patient was given both ER and EC in one refill, being told by the pharmacy that the two formulations only differed in color. Three other cases documented incorrectly the formulation dispensed, which created confusion for the prescriber, but did not result in problems for the patient., Availability of divalproex-ER and EC in identical dose strengths has created some confusion among healthcare providers and pharmacies, resulting in patient complications. Prescriptions for EC vs ER require vigilance by all, including the patients receiving the prescriptions. Inadvertent substitution of EC for ER has been documented to have deleterious clinical impact. Additional education of pharmacists may be needed to minimize dispensing errors of this type., (Supported by Abbott Laboratories.)