In just the past few years, fears of deadly flu pandemics have turned the influenza-fighting drug called Tamiflu into a worldwide household name.
The World Health Organization has declared the antiviral an "essential medicine" like penicillin and ibuprofen. Since 2005, when bird flu spread globally, it has been prescribed to more than 18 million people in the U.S., including almost 7 million children.
During this year's busy flu season, Tamiflu is so popular that federal regulators recently warned of possible shortages of the liquid form often given to children.
But for all the hype, it's hardly a wonder drug. Medical experts internationally are debating whether its power against a virus that kills thousands annually was oversold.
At best, experts say, Tamiflu can shorten the misery of the flu by a day or so — which could make a big difference in the most vulnerable patients, such as frail seniors.
But at about $10 a pill it's expensive, and most people recover just fine without a drug whose reported harmful effects include rare but serious hallucinations in kids.
Still many Americans — encouraged by catchy TV ad campaigns — equate Tamiflu with instant relief.
"There is a perception that, 'I need this medicine to make it go away,' " said Dr. John Sosa, a family physician at the HealthPoint Medical Group's office in the Westchase area of Tampa. "Unfortunately, that's just not the case."
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Tamiflu is the brand name for oseltamavir, one of two antiviral drugs available in the United States to fight today's flu strains. Offered in pill and liquid form, it recently was approved for infants as young as 2 weeks.
The other antiviral, Relenza, is an inhaled powder that can't be used as widely. But neither of the drugs — known as neuraminidase inhibitors — can just wipe out flu. They prevent infected cells from releasing viruses, which would subsequently infect more cells. That's why the drugs need to be given early; as the flu runs its course and the body heals itself, they have little impact.
"People think that it's a curative — equivalent to an antibiotic, where it's going to kill off the bug or a virus, which unfortunately it isn't," Sosa said. "It slows down the replication of the virus."
How well Tamiflu does even that, however, is the subject of intense debate.
In 2009, the British government commissioned a review of neuraminidase inhibitors by the Cochrane Collaboration, a group of experts whose systematic reviews of medical treatments are considered the gold standard of evidence-based research.
Cochrane researchers found that much of the clinical trial data on Tamiflu was never vetted publicly. They asked to see the company's internal studies.
Three years later, they still are waiting.
"This means that taxpayers in the United Kingdom and around the world have spent billions of dollars stockpiling a drug for which no one except the manufacturer has seen the complete evidence base," the British journal BMJ editorialized in October.
The journal has made Tamiflu the centerpiece of a first-of-its-kind campaign calling for greater scrutiny of pharmaceutical trials.
"What has Roche got to hide?" the journal asked of the drug's parent company.
Roche representatives plan to set up an advisory board of experts to review the data. "We believe this approach is a fair and transparent way of addressing this public debate," officials told the Tampa Bay Times in a statement.
Based on available evidence, the drug shortens flu symptoms by about 21 hours, Cochrane experts reported. It did not reduce hospitalizations due to flu, they found.
Their analysis supports the U.S. Food and Drug Administration's description of Tamiflu's performance as "modest."
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In light of the debate, the U.S. Centers for Disease Control and Prevention reaffirmed its support for using Tamiflu, especially for the very young, elderly and chronically ill patients at risk of severe illness.
"Most otherwise healthy people who get the flu, however, do not need to be treated with antiviral drugs," the CDC website notes.
Downsides to consider: A 10-pack of 75 mg capsules costs $101.50, according to drugmaker Genentech, a member of the Roche group.
Covered by most insurance plans, including Medicare and Medicaid, the average copay is $35, the company says. It offers a $10 coupon at Tamiflu.com.
Common side effects of Tamiflu include nausea and vomiting.
But while rare, there have been more serious reports of seizures, hallucinations, confusion and other abnormal behavior, especially in children and adolescents.
These concerns prompted U.S. regulators to add a warning to the drug's safety information. Grace Tharp of Gainesville found out why last month.
After her first dose of Tamiflu, the 12-year-old told her mother that she was seeing a giant wax figure. She heard a group of people yelling in her ear.
"It's just the two of us," mother Chris Tharp assured her.
The hallucinations continued. At the emergency room, doctors said Tamiflu was responsible, her mother said. The frightening visions and sounds went on for 36 hours, though Grace never took a second dose.
Her pediatrician later told her mother that influenza could have been to blame, too. But Chris Tharp doubts her daughter had fever-related delirium, as her temperature was not high.
"This is the 'it' drug this year. Every kid who goes to the pediatrician with the flu is walking away with a 10-pack of Tamiflu," said Tharp, 43, who hosts a morning radio show in Gainesville.
She cautioned the parents of otherwise healthy children to think twice before taking it.
"If you have Tylenol and Gatorade, you are just as well equipped to get through (the flu) and not have to deal with this," she said, referring to her daughter's scary episode.
At All Children's Hospital in St. Petersburg, Dr. Juan Dumois, chairman of infectious disease, has heard of the concern, but hasn't seen a child develop hallucinations while on Tamiflu.
"It's very rare," he said.
When his 14- and 17-year-old sons recently had flu, they took Tamiflu without a problem. "They got a little nausea when they took the pill, but it wasn't bad enough to even affect their appetites," he said.
Dumois and other infectious disease experts say the best flu fighter is prevention, in the form of flu vaccines, hand hygiene, and staying home when you're ill.
Forgoing prevention because you think Tamiflu is your backup plan is a common misperception, and a mistake.
"It can provide a false sense of security,'' Dumois said, "if people think that once they're on it, nothing bad can happen."
Times researcher Caryn Baird contributed to this story.