Many U.S. teens have lent or borrowed prescription medications such as antibiotics and acne medication, a survey suggests.

When researchers interviewed 529 people aged 12 to 17 in 11 U.S cities or suburbs, they found one in five reported they had borrowed or lent a prescription.

A third of the teens who took a borrowed prescription did not tell their doctor, the team said in this week's online issue of the Journal of Adolescent Health.

"Other researchers have studied people selling prescription drugs, but we looked at people with good intentions, trying, for instance, to help a friend who lacked money or transportation for a doctor's visit," co-author Chris Mayhorn, a professor of psychology at North Carolina State University, said in a release from the Center for the Advancement of Health.

Increased antibiotic resistance is also possible, since neither the lender nor the borrower was likely to take the full course of the drugs, the researchers noted.

Not telling a doctor about swapping medications could lead to drug interactions or other problems.

Dangerous moves

For example, the acne medication Accutane has been linked to birth defects. Someone could lend the drug to a friend who is pregnant but doesn't yet realize it, the researchers said.

About 32 per cent of the youths who took a borrowed medication said they eventually saw a doctor because the drugs did not resolve the problem.

Study participants were asked about whether they gave or received any warnings or instructions with the medication. Almost two in five borrowers said they experienced side-effects.

In 2001, Canadian researchers reported nearly 15 per cent of teens who were prescribed Ritalin or other stimulants have given away at least some pills, and more than seven per cent sold the pills.

Earlier research suggests almost 40 per cent of U.S. adults have also lent or borrowed prescription drugs.

The latest study also looked at sharing of antibiotics, birth control pills and allergy medications among young people.

"Efforts to reduce the prevalence and consequences of adolescent medication sharing may be justified, including training providers to ask specifically about borrowed medication and educating patients about proper use of prescriptions and risks of sharing," the study's authors concluded.

"Development of messaging related to sharing, for example, within product packaging or public awareness campaigns, may merit further consideration."

The findings are important for doctors, prevention groups, school counselors, parents and youth, Melissa Haddow, executive director of the Community Partnership of the Ozarks, said in a release.

Study participants were interviewed in English or Spanish.

The study was funded by the National Center on Birth Defects and Developmental Disabilities.