Prescription Errors & Decimal Points

Posted by Pharmacist on July 23, 2010

The small decimal point has the power of providing the precise medication for someone or wreaking havoc by providing too much or too little medication to patients.  Proper decimal point placement cannot be overstated.  Prescriptions that are faxed, written or typed on no carbon-required forms, or written on lined paper all carry the risk of a decimal point being missed.

Decimal points should never be left alone, but always preceded by a zero.  This will ensure that the decimal point is more visable.  For example, with no leading zero, “Haldol .5 mg” could easily be misinterpreted as “Haldol 5 mg” or “Risperdal .5 mg” easily interpreted as “Risperdal 5 mg”.

Conversely, a whole number should never be followed with a decimal point and a zero.  This can easily cause 10 fold overdose.  For example, “Coumadin 1.0 mg” can easily be misinterpreted as “Coumadin 10 mg”.

To avoid errors in decimal point placement, the following rules should be in place:

-Any concentrations or strengths less than zero should have a leading zero in front of the decimal point.

-A decimal point and a trailing zero should never follow a whole number.

-Educate staff about the dangers or using naked decimal points and trailing zeros.

-Do not allow staff members to omit leading zeros or trailing zeros when reducing oral prescriptions to writing.

-Ensure that pharmacy and prescriber electronic order entry screens, preprinted prescriptions, and computer generated labels do not use any dangerous decimal dose expressions.

-If a satisfactory alternative is available, eliminate the use of decimal points.  For example, use 125 mcg instead of 0.125 mg , 500 mg instead of 0.5 g, and 2 ½ mg instead of 2.5 mg.

-Identify any drugs with 10 fold differences in dosage strength, such as Coumadin 1 mg and 10 mg, Levothyroxine 25 mcg and 250 mcg, and Cytomel 5 mcg and 50 mg.  Make sure that any drugs on this list are double checked to ensure correct dosage strength.

-Decimal points can be easily missed when prescriptions are faxed.  Have the pharmacist check and verify all faxed prescriptions.

-Eliminate lines on NCR forms so that decimal points are more clearly distinguished.

More information concerning decimal point placement as well as a listing of the ISMP (Institute for Safe Medicine Practices) List of Error-Prone Abbreviations can be found by clicking the following link.

Institute for Safe Medicine Practices

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