Errors in the use of medication dosage equations

Calculation errors in prescribing are a well-recognized problem; however, no systematic studies of actual errors involving calculation or other errors in the use of drug dosage equations are available.

To characterize the nature and potential adverse consequences of actual prescribing errors involving dosage equations.

Analysis of the characteristics of 200 consecutive prescribing errors with potentially adverse outcomes involving dosage equations.

Tertiary care teaching hospital.

Potential adverse outcomes, prescribing service, medication class, and the process point at which the error was made.

Errors most commonly involved children (69.5%) and antibiotics (53.5%). Forty-two percent of errors were considered to put the patient at risk for a serious or severe preventable adverse outcome. Errors in decimal point placement, mathematical calculation, or expression of dosage regimen accounted for 59.5% of dosage errors. The dosage equation was wrong in 29.5% of dosage errors.

The use of equations to determine medication dosages presents considerable risk to patients for errant dosing and subsequent adverse events or therapeutic failure. Errors may occur in any component of a dosage equation. Health care organizations should implement procedures to reduce the risk for errors resulting from the use of dosage equations.