Antibiotics: Phenoxymethylpenicillin remains first line due to its high effectiveness, no reported resistance, and narrow spectrum of activity. In the event of non-availability, amoxicillin, macrolides and cefalexin are alternative agents in decreasing preference. Antibiotic treatment length for sore throat should follow NICE guidance. For phenoxymethylpenicillin: Five days of phenoxymethylpenicillin may be enough for symptomatic cure, but a 10-day course may increase the chance of microbiological cure
See also the Centor Criteria
DECEMBER 2022 UPDATE: Given the current high prevalence of group A Streptococcus (GAS) and an increase in invasive groups A Streptococcus (iGAS), a decision to treat tonsillitis with antibiotics in CHILDREN over 3 years old can be guided by a FeverPAIN score of 3 or more (this is a lower threshold in light of increased invasive Group A Streptococcus incidence and deviates from NICE Guidelines) in combination with clinical judgement.
This updated guidance is valid until end of January 2023 when it will be reviewed. For more information see Group A streptococcus in children - Interim clinical guidance summary