A high dosage of Tamiflu (oseltamivir) for patients with critical illness is unlikely to be required for the treatment of pandemic (H1N1) influenza, a new study has found.
The study has appeared in Canadian Medical Association Journal (CMAJ).
The study goes against the World Health Organization (WHO) guidelines, which say all critically ill patients should be treated with Tamiflu and if the patient was unresponsive to standard doses, or critically ill, a higher dose should be considered. As critically ill patients may have gastrointestinal absorption issues, guidelines suggest higher doses of Tamiflu.
The CMAJ study looked at the gastrointestinal absorption of Tamiflu in 44 patients, 18 years of age or older, with suspected or confirmed pandemic (H1N1) influenza who were admitted to nine ICUs in the two Canadian cities of Winnipeg and Ottawa and Tarragona, Spain, because of respiratory failure.
"Studying the absorption ability of Tamiflu in the critically ill became a priority with the large number of patients needing ICU and ventilation support,"
Lead author Dr. Anand Kumar, Health Sciences Centre, University of Manitoba and coauthors, write: "Also, the number of obese patients suffering from H1N1 related critical illnesses were large which raised the question about whether the dose should be adjusted upwards with increased body weight."
Blood sampling suggested that the 75 mg twice daily dosage of Tamiflu was well absorbed in critically ill patients with respiratory failure. Blood levels of the antiviral were similar or higher than levels in ambulatory patients with a similar dosage. Patients with kidney dysfunction requiring dialysis needed an adjusted dose but adjustment for obesity was not required.
The authors conclude: "The findings of this study suggest that an increased Tamiflu dosage is unlikely to be necessary in such cases based on either insufficient drug absorption or altered distribution pharmacokinetics."