United States of America. Numerous errors have been reported when prescribers order medications using decimal dosages. Recently, a physician ordered “morphine 2.5-7.5 mg and hydroxyzine 25-50 mg IM every 3-4 hours prn for severe pain”. A pharmacist and nurse misinterpreted the order. Both did not notice the decimal point and subconsciously interpreted the orders as meperidine 25-75 mg rather than 2.5-7.5 mg of morphine. Fortunately, another pharmacist caught the error during order entry verification and the dose was corrected.

The same type of error has been reported when Compazine and Coumadin have been ordered as 2.5 mg, but misinterpreted as 25 mg. In these situations, using fractions such as 22 mg or 72 mg should be considered.

Reference: ISMP Medication Safety Alert! Vol. 3, Issue 24, 1 December 1998.