From the March 2008 issue

A pharmacy student on rotation at ISMP recently told us about confusion that is occurring between immediate-release metoprolol tartrate (LOPRESSOR) and extended-release metoprolol succinate (TOPROL-XL), both of which are used to treat hypertension and angina pectoris. Since the introduction of generic formulations of Toprol-XL, her pharmacy has been receiving prescriptions that identify the drug to be dispensed only as “metoprolol.” Prescribers are not clearly indicating which dosage form they want patients to receive. This creates a situation in which the wrong dosage form could be dispensed (e.g., immediate release instead of extended release). We also have learned that prescribers are selecting the incorrect dosage form from computer screen pick lists in electronic prescribing systems. If the incorrect product is prescribed or dispensed, it could be taken for 30 days or if dispensed by mail order for 90 days.

To reduce the risk of mix-up, educate your colleagues about the possibility of confusing these products. Prescribers should explicitly state which dosage form they want dispensed. This could be done by indicating the salt with the name (i.e., metoprolol tartrate or metoprolol succinate) or the words “immediate release” or “extended release.” Pharmacists should communicate with patients and/or verify with the prescriber which metoprolol product is to be dispensed if it is not specified on the prescription. They should also label their inventory to differentiate immediate-release and extended-release products from one another. Be sure patients understand that various dosage forms of metoprolol exist and help them understand which one has been prescribed for them. With this information, they will be armed to provide a final verification any time the medication is dispensed.