Drugs

No Need To Stock Up: Antiviral Medication Tamiflu Effective In Single And Double Doses

Single Dose of Tamiflu is Enough
New study determines there is no difference between taking a single or double dose of antiviral Tamiflu to treat severe influenza, result are the same. Tamiflu | Justin Trask Vimeo

When it comes to Tamiflu (generic name oseltamivir), more medication is not necessarily more effective.

Tamiflu is an antiviral medication available by prescription only to treat influenza by reducing the severity of symptoms and speeding up recovery. It is approved for people two weeks of age and older and may reduce the chance of getting the flu. Until 2010, the drug was approved only for emergency use in infants, but now is widely available for all to use by prescription. To be effective, Tamiflu must be used within 48 hours of symptom onset.

Tamiflu use been associated with a 61 percent reduction in hospital admissions, according to the U.S. Centers for Disease Control and Prevention (CDC). Since its success, there has been debate over the appropriate dosage. While infants are generally given 30 milligrams and children are given 45 milligrams, the adult dosage remains controversial. Should adults take 75 milligrams twice daily or double that, taking 150 milligrams twice daily? Currently, the standard dose determined by the U.S. Food and Drug Administration for adults is 75 milligrams, twice daily for five days.

Could a double dose of the antiviral be more effective?

In a large randomized control trial of 326 patients published in the British Medical Journal, the efficacy single and double doses of Tamiflu in treating influenza were compared. Half of participants were given single doses while the other half were given double doses. They were tested on days 5 and 10 of treatment for antigens for the influenza virus. Antigens are an important part of a body's immune response, as they mark foreign bodies to be destroyed by the body's immune system. Antigens against the virus are associated with a smooth recovery form the flu.

The two groups showed little difference in the incidence of adverse reactions. About 17 percent of both single and double dose groups experienced adverse effects, including rashes, organ failure, and septic shock. Mortality rates were similar for both dosing groups: 6 percent of those receiving a double dose and 7 percent of those receiving a single dose died from complcations caused by the virus. 

On day 5, there was a slight difference between groups for the presence of virus. Less virus present generally means a patient is fighting off the viral infection and is likely to recover sooner. Patients in the double dose group had a 4.2 percent higher likelihood of being negative for the presence of the virus than single dose patients. However, this small difference is not conclusive enough to say whether a double dose is more beneficial than a single dose.

While Tamiflu has been proven for use against influenza virus, including swine and avian flus, there are no apparent benefits to a double dose instead of a standard dose. 

With seasonal flu reaching pandemic levels every winter, it is important to note that Tamiflu should not replace a flu shot. Tamiflu should be used when symptoms first appear in order to be effective. Researchers have shown that the standard dose will generally suffice if taken at the first sign of symptoms, and doing so will preserve the stock of the medication during an outbreak.

 

Source: Farrar J. Effect of double dose oseltamivir on clinical and virological outcomes in children and adults admittedto hospital with severe influenza: double blind randomised controlled trial. BMJ. 2013.

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