Source:  US Food & Drug Administration

Prescribing physicians and pharmacists should be alert for potential dosing errors with Tamiflu (oseltamivir) for Oral Suspension. Why? Because despite the fact that we were supposed to have been a metric society about 30 years ago, we aren’t.  What does that have to do with anything?  Quite a bit apparently.

U.S. health care providers usually write prescriptions for liquid medicines in milliliters (mL) or teaspoons, while Tamiflu is dosed in milligrams (mg). The dosing dispenser packaged with Tamiflu has markings only in 30, 45 and 60 mg. The FDA has received reports of errors where dosing instructions for the patient do not match the dosing dispenser.

Health care providers should write doses in mg if the dosing dispenser with the drug is in mg.
Pharmacists should ensure that the units of measure on the prescription instructions match the dosing device provided with the drug.

If prescription instructions specify administration using mL, the dosing device accompanying the product should be replaced with a measuring device (e.g., a syringe) calibrated in mL.

Specific Considerations for Tamiflu Dosing for Children over 1 Year of Age:

  • Dosing should be prescribed in mg according to information provided in the table below.  Caregivers for children should use the dosing dispenser packaged with the medication, unless otherwise directed by a health care provider.
  • If the dosing dispenser packaged with Tamiflu oral suspension is lost or damaged, or if the prescriber wishes to use volume-based dosing, appropriate dosages in mL are also provided in the table. In these cases the prescriber and pharmacist should ensure that a dosing dispenser, such as an oral syringe calibrated in mL, is given to the patient or caregiver with instructions for use. The dosing dispenser packaged with the product should be discarded.
  • Prescribers should avoid prescribing Tamiflu oral suspension in teaspoons. This can lead to inaccurate dosing. If a prescription is written in teaspoons, the pharmacist should convert the volume to mL and ensure that an appropriate measuring device, such as an oral syringe calibrated in mL, is provided. The dosing dispenser packaged with the product should be discarded.

Dose of Tamiflu for Oral Suspension (12 mg/mL) for Treatment of Influenza
in Pediatric Patients 1 Year or Older by Weight

Body Weight (kg) Body Weight (lbs) Recommended Dose
for 5 Days
(If using the dosing device supplied with the product)		 Dose (mL)
(If using a syringe marked in mL or cc)		 Number of Bottles of Tamiflu needed to Obtain the Recommended Doses for a 5 Day Regimen
< 15 kg < 33 lbs 30 mg twice daily 2.5 mL 1
>15 kg to 23 kg >33 lbs to 51 lbs 45 mg twice daily 3.8 mL 2
>23 kg to 40 kg >51 lbs to 88 lbs 60 mg twice daily 5.0 mL 2
>40 kg >88 lbs 75 mg twice daily 6.2 mL 3

A big deal actually if you think about the potential for overdosing.

~Posted by D.M. Schwadron, Esq.