Tamiflu for Influenza: Benefit Still Unproven

NOVEMBER 10, 2015
As we enter the height of flu season, many pharmacists are providing valuable counseling to patients with influenza or flu-like symptoms.
 
When it comes to oseltamivir (Tamiflu), however, it is important to remember that this neuraminidase inhibitor still has limited use for flu, despite what direct-to-consumer marketing tells patients.

Back in April 2014, the Cochrane Acute Respiratory Infections Group published updated systematic reviews that included information containing previously withheld patient data from Roche, the manufacturer of Tamiflu, and GSK, the manufacturer of zanamivir (Relenza).1,2

The first publication was a systematic review of oseltamivir randomized, controlled trials in adults and children. 
 
While oseltamivir shortened the duration of symptoms by 16.8 hours compared with placebo—a statistical but perhaps not a clinical benefit—it did not reduce hospital admissions, incidence of pneumonia, complications, or flu transmission when taken as prophylaxis. In addition, the drug was linked to more nausea, vomiting, psyciatric events and headache during that shorter duration of symptoms.

The second systematic review had similar methodology, but it examined zanamivir. Similarly, there was a shortened duration of symptoms (14.4 hours) and a small (1.98%) decrease in flu transmission, but no benefit in reducing the incidence of confirmed pneumonia or other complications.

Despite the reduction in flu duration, the adverse events associated with oseltamivir are concerning. Headache, in particular, was demonstrated to occur in a dose-escalating fashion, which increases concerns for further neuropsychiatric complications in patients receiving a high dose (150 mg) or those with renal impairment.3

When examining the totality of evidence and considering the previous experience of such evidence being withheld from the public, it is hard to understand why the evidence analyzed by a trusted group is disregarded, and why yet another $1.3 billion will be spent restocking Tamiflu once the current supply expires in the near future.4

References
  1. Heneghan CJ, Onakpoya I, Thopson M, Spencer EA, Jones M, Jefferson T. Zanamivir for influenza in adults and children: systematic review of clinical study reports and summary of regulatory comments. BMJ. 2014;348:g2547.
  2. Jefferson T, Jones M, Doshi P, Spencer EA, Onakpoya I, Heneghan CJ. Oseltamivir for influenza in adults and children: systematic review of clinical study reports and summary of regulatory comments. BMJ. 2014;348:g2545.
  3. Torjesen I. Cochrane review questions effectiveness of neuraminidase inhibitors. BMJ. 2014;348:g2675.
  4. Krumholz HM, Hines HH. Neuraminidase inhibitors for influenza: The whole truth and nothing but the truth. BMJ. 2014;348:g2548.


Craig Cocchio, PharmD
Craig Cocchio, PharmD
Craig Cocchio, PharmD, BCPS, is an Emergency Medicine Clinical Pharmacist at Trinity Mother Frances Hospital in Tyler, Texas. Follow on Twitter @iEMPharmD and on his blog at empharmd.blogspot.com
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