US Pharm. 2009;34(12):54-55.

Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Carefully separate the capsule body and cap and transfer the contents of the required number of Tamiflu 75-mg capsules into a clean mortar. Triturate the granules to a fine powder. Add about one-third of the specified amount of vehicle to the mortar, and triturate the powder until a uniform suspension is achieved. Transfer the suspension to an amber glass or polyethylene terephthalate bottle that has been properly calibrated for the final volume. Add another one-third (approximate) of the vehicle to the mortar, rinse the pestle and mortar, and transfer the contents to the bottle. Repeat the rinsing with the sufficient vehicle, adding it to final volume in the calibrated container. Place a child-resistant cap on the bottle. Shake well, then package and label.  

Use: Tamiflu oral suspension is indicated for prophylaxis and treatment of uncomplicated influenza infection in patients aged ≥1 year.3

Packaging: Package in tight, light-resistant containers.  

Labeling: Shake well before use. Keep out of the reach of children. Discard after ____ [time period].

Stability: Cherry syrup (Humco) and Ora-Sweet SF formulations--Refrigeration: stable for 5 weeks (35 days) when stored in a refrigerator at 2°C to 8°C (36°F to 46°F). Room temperature: cherry syrup stable for 5 days when stored at room temperature of 25°C (77°F); Ora-Sweet SF stable for 35 days when stored at room temperature.

PCCA-Plus, acacia syrup, and methylcellulose 1% solution formulations--Refrigeration: stable for 90 days when stored in a refrigerator at 2°C to 8°C (36°F to 46°F). Room temperature: stable for 90 days when stored at room temperature of 25°C (77°F).

Note: The time periods listed above are recommended by Ford et al.2 Shorter dating is suggested, however, as this preparation is intended for short-term storage and use.

Other vehicles--Stability information is not available for other vehicles. Therefore, the USP General Chapter <795> standard would be to assign a beyond-use date of 14 days for the preparation when stored in a refrigerator at 2°C to 8°C (36°F to 46°F).

Quality Control: Quality-control assessment can include weight/volume, pH, specific gravity, active drug assay, color, rheologic properties/pourability, physical observation, and physical stability (discoloration, foreign materials, gas formation, mold growth).4  

Discussion: It has been announced that Tamiflu capsules will be manufactured to meet current demands and that pharmacists will compound the oral suspension for consumers. The manufacturer can mass-produce many more capsules than the oral suspension formulation in a given time period. The labeling for Tamiflu includes instructions on how to prepare an oral suspension using two different vehicles, as presented above.1

Different vehicles may be used and different concentrations may be compounded, according to the needs of the physician or patient and the availability of vehicles. The stability implications must be considered in the event that other concentrations are compounded.

Oseltamivir phosphate (C16H28N2O4.H3PO4, MW 420.40) is an ethyl ester prodrug available as a capsule containing 75 mg oseltamivir for oral use as an antiviral (influenza). It is manufactured as a capsule and as a powder for oral suspension. The suspension, when reconstituted according to labeling instructions, contains 12 mg/mL oseltamivir. Oseltamivir phosphate occurs as a white crystalline solid. The capsules also contain pregelatinized starch, talc, povidone K30, croscarmellose sodium, and sodium stearyl fumarate; the capsule shells contain gelatin and coloring agents.

REFERENCES

1. Tamiflu.com. Dosing, administration and storage: extemporaneous preparation.  
www.tamiflu.com/hcp/dosing/ extprep.aspx. Accessed November 13, 2009.
2. Ford SM, Kloesel LG, Grabenstein JD. Stability of oseltamivir in various extempor-aneous liquid preparations. IJPC. 2007;11:162-174.
3. Physicians' Desk Reference. 63rd ed. Montvale, NJ: Thomson Reuters; 2009:2649-2654.
4. Allen LV Jr. Standard operating procedure for performing physical quality assessment of oral and topical liquids. IJPC. 1999;3:146-147.

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