Doctors treating children with a throat infection caused by Streptococcus bacteria should use newer drugs, not penicillin, researchers say.
Penicillin's role being questioned
Paediatricians at the US' University of Rochester Medical Centre said new antibiotics were three times better.
But UK GPs said penicillin worked well and there was no immediate reason to switch over.
"Strep throat" is passed by personal contact. School-age children seem particularly vulnerable.
A new class of antibiotics, called cephalosporins, can be as cheap as penicillin and have a similar effect, the Rochester researchers said in the journal Pediatrics.
They examined a number of previous studies, covering 7,000 children, to compare the effectiveness of the two drugs.
Both penicillin and some first generation cephalosporins, such as Cephalexin and Cefadroxil, are "narrow spectrum", which means they are targeted enough to tackle the bacteria but not so strong that they cause resistance.
Resistance can lead to the creation of a superbug and is one of the reasons penicillin has traditionally been used.
However, the researchers said the newer drugs both met this requirement and were more effective in attacking the bacteria that cause strep throat.
Dr Janet Casey, a paediatrician and lead author of the study, said: "Children who have strep throat will have a superior outcome if they receive cephalosporin rather than penicillin.
"Some penicillin proponents don't spend much time in the paediatrician's office. Many of these doctors aren't in the trenches anymore seeing sick children every day.
"Those of us who are see how frustrating it is for families who need to come back for additional treatments who wonder why the antibiotic their child took didn't work."
The findings go against long-established advice from the World Health Organization but Dr Casey called for guidelines to be reviewed.
However, Dr George Rae, a GP and a member of the British Medical Association's prescribing committee, said the research "flies in the face" of what doctors have been taught and have found to work in practise.
He said: "In my experience, I have found streptococcal sore throats have resolved using penicillin. Unless guidelines are produced by NICE or whoever, I am happy with the way I do it."
He stressed that 90% of sore throats are viral and do not require antibiotics.