A shortage of commercially available Tamiflu® (oseltamivir phosphate) oral suspension is contributing to dosing errors in healthcare facilities. On October 15, 2009, the Institute for Safe Medication Practices (ISMP) alerted healthcare professionals about a risk of overdoses and underdoses related to the concentration of pharmacy-compounded Tamiflu being dispensed in response to shortages of the manufacturer’s oral suspension.¹ As of October 20, 2009, two reports have been submitted to the Pennsylvania Patient Safety Authority describing dosing errors related to the concentration of Tamiflu available from inpatient pharmacies. In each case, it was thought that the commercially available 12 mg/mL product and not a pharmacy-compounded 15 mg/mL oral suspension would be dispensed. Both pediatric patients received overdoses without harm.

The patient was ordered 60 mg of Tamiflu oral suspension, which was profiled using the 12 mg/mL concentration. 15 mg/mL was dispensed and 5 mL were administered. The error was noted and corrected. The physician was aware.

The patient started on Tamiflu 12 mg/mL oral suspension at a dose of 45 mg (equals 3.75 mL). 3.75 mL were drawn up using the 15 mg/mL concentration, making a dose of 56.25 mg.

Roche commercially manufactures Tamiflu oral suspension in a 12 mg/mL concentration (oseltamivir base) for pediatric and adult patients who have difficulty swallowing capsules (see Figure). In light of the influenza epidemic, pharmacies in some areas across the state and the nation have been unable to purchase the commercial oral suspension from the manufacturer or drug wholesalers. As a result, pharmacists have begun to compound the product according to the U.S. Food and Drug Administration-approved directions for the emergency compounding of an oral suspension listed in the Tamiflu labeling (http://www.tamiflu.com/hcp/dosing/extprep.
aspx). The extemporaneously prepared suspension utilizes the powder in Tamiflu capsules, which remain available for purchase. However, use of the compounding directions found in the labeling results in a 15 mg/mL oseltamivir base concentration, not the commercially available 12 mg/mL base concentration. More information about Tamiflu as well as a free Webinar illustrating the emergency compounding process can be found at the influenza section of the RocheExchange (http://www.rocheexchange.com/influenza).

  Figure. Tamiflu® Oral Suspension 12 mg/mL 

Alert healthcare practitioners in your facility to this situation. At this time, ISMP recommends that prescribers communicate suspension doses in mg rather than by volume.¹ Computerized prescriber order-entry systems should only list the available concentration on computer selection screens. Pharmacy computer systems should alert practitioners to verify the dose and concentration to be dispensed. Proactive, direct communication between the prescriber and pharmacist may be necessary to ensure the intended dose reaches the patient. Include the patient specific dose with corresponding number of mL and the concentration of liquid provided on the pharmacy-generated label applied to the dispensed product.²

If pharmacists are experiencing a shortage of commercial Tamiflu oral suspension, ISMP suggests proactively communicating with prescribers at health system-owned physician practices and other area medical practices to advise them of the shortage and steps to reduce the possibility of dosing errors when dispensing the pharmacy-compounded solution. As an alternative, Tamiflu capsules may be opened and the contents (30 mg, 45 mg, and 75 mg) mixed with sweetened liquids, such as regular or sugar-free chocolate syrup, for single doses.³

Notes

1. Institute for Safe Medication Practices.Tamiflu oral suspension shortage contributing to dosing errors [special alert]. ISMP Med Saf Alert [online]. 2009 Oct 15 [cited 2009 Oct 22]. Available from Internet: http://www.ismp.org/safetyalerts/20091015-Tamiflu.asp.
2. Institute for Safe Medication Practices. Principles of designing a medication label for oral liquids for patient specific, inpatient use [online]. [cited 2009 Oct 22]. Available from Internet: http://www.ismp.org/Tools/guidelines/labelFormats/liquidSolids.asp.
3. Roche Laboratories, Inc. Tamiflu® (oseltamivir phosphate) [full prescribing information] [online]. 2008 Aug. [cited 2009 Oct 20]. Available from Internet: http://www.gene.com/gene/products/information/tamiflu/pdf/pi.pdf.