Information on how to prescribe medications to children is scarce, and doctors often rely on the flawed assumption that children are simply smaller versions of adults when doing so.

In reality, drugs act much differently in children, yet few studies have been conducted to determine their effectiveness, safety and proper dosages.

Federal regulators have enticed or forced pharmaceutical companies to conduct studies on more than 200 drugs geared for children, but more than two-thirds of the medications given to children remain untested. Among those that were tested, it was found that:

• One-fifth of drugs that work in adults are ineffective in children
• One-fifth of the drugs were being prescribed at the wrong dosage
• One-third of the drugs caused unexpected side effects, some of which were potentially fatal

Other alarming factors discovered were that children process drugs more quickly than adults do, and because children are still developing, drugs could stunt physical growth or impair emotional and cognitive development.

Researchers have identified categories of drugs that they say should be a priority for testing. These include drugs to treat cancers, infections, asthma, high blood pressure and hyperactivity, among others.

Hurdles still remain, however. Drug companies are often reluctant to study pediatric drugs because they represent only a small fraction of the market. Further, the drugs must be evaluated in four separate age groups, which makes analyzing data more difficult.

Parents are also wary about letting their children participate in studies for fear that they will be used as guinea pigs.

"They don‘t want their child to be thought of as a guinea pig or a rat in a study. What I try to explain is that if they are receiving a medication that hasn‘t been studied, then they are essentially participating in an experiment anyway," said Robert M. Ward, director of the pediatric pharmacology program at the University of Utah.