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FDA Advise-ERR: Avoiding topotecan 10-fold overdoses

The US Food and Drug Administration (FDA) and ISMP have received reports of medication errors involving 10-fold topotecan overdoses. One error was due to misreading an order caused by omission of the leading zero in the dose. The topotecan dose was written as .7 mg instead of 0.7 mg, and the patient received 7 mg of the drug in error. 

Four other 10-fold overdoses have also been reported. None of these reports indicated the root causes. However, the overdoses in three of the cases may have occurred because the decimal point in the dose was overlooked when interpreting the topotecan order. In one case, a patient was prescribed a 2.5 mg dose but received a 25 mg dose. In another, the physician ordered 2.9 mg but the nurse administering the topotecan misread the dose and the patient received 29 mg. Another patient was supposed to receive 2.4 mg of topotecan, but the order was written for a 24 mg dose. In the fourth case, a patient received 40 mg/m2 instead of 4 mg/m2. This overdose may have stemmed from a dose on an order with a trailing zero.

Recommendations

Considering that the recommended doses for topotecan are 1.5 mg/m2 (for the intravenous infusion)1 and 2.3 mg/m2 (for the oral capsules),2 healthcare practitioners should heighten their index of suspicion and question any topotecan doses greater than 5 mg.* We also recommend the following:

  • Always include a leading zero (e.g., topotecan 0.7 mg) and avoid using trailing zeros (e.g., topotecan 2.0 mg) when expressing dosing, as the dose may be misread leading to dosing errors. 

  • In addition to the total calculated dose in milligrams based on the patient’s body surface area, prescribers should be encouraged to include the intended dose in mg/m2 to allow other healthcare practitioners to verify that the calculated dose is correct.

  • Consideration should be given to using standardized order sets when ordering topotecan to avoid dose confusion.

References

  1. Daily Med. May 2011. The National Library of Medicine. March 21, 2013. Daily Med. October 2011.
  2. The National Library of Medicine. March 21, 2013. 

*Editor's note: Computer alerts for topotecan doses above 5 mg should also be considered. FDA Advise-ERR was provided by Tingting Gao, PharmD, BCPS, James Schlick, RPh, MBA, and Todd Bridges, RPh, of FDA’s Office of Surveillance and Epidemiology, Division of Medication Error Prevention and Analysis.