Group A Streptococcal Pharyngitis

Clinical Snapshot

Group A streptococcal (GAS) pharyngitis is acute inflammation of the pharynx and/or tonsils caused by Streptococcus pyogenes. It is the most common bacterial cause of acute sore throat, concentrated in school-aged children (roughly 5–15 years old) and most active from late autumn through spring, but in every age group most acute pharyngitis is still viral regardless of GAS colonization status.^[1] The central clinical task is therefore not simply recognizing pharyngitis — it is working out whether GAS is actually the cause before reaching for an antibiotic. Untreated or inadequately treated GAS pharyngitis is now understood as a self-limited illness for the great majority of patients; the reason antibiotics are still recommended when GAS is confirmed is prevention of acute rheumatic fever (ARF) and suppurative complications such as peritonsillar abscess, not primarily faster symptom relief, which is at most a modest secondary benefit.^[2]

Recognize the Condition

Typical presentation

Acute, painful sore throat, usually of abrupt onset.
Fever.
Tender, swollen anterior cervical lymph nodes.
Erythematous pharynx and tonsils, with or without tonsillar exudate.
A fine, sandpaper-like scarlatiniform rash (scarlet fever) in a minority of patients — a palatal petechiae and "strawberry tongue" may accompany it.
Headache and abdominal pain (sometimes with vomiting) are common accompanying complaints in children.

Culture-confirmed streptococcal pharyngitis with tonsillar exudate and erythema in a child

Culture-positive GAS pharyngitis with typical tonsillar exudate. (James Heilman, MD, CC BY-SA 3.0, Wikimedia Commons)

No single symptom or exam finding reliably distinguishes GAS from viral pharyngitis — this is precisely why a pretest-probability score plus confirmatory testing is used rather than treating on clinical impression alone (see Assessment & Diagnosis).^[1] The absence of typical viral upper respiratory features is itself a useful clue in favour of GAS: cough, rhinorrhea, hoarseness, conjunctivitis, oral ulcers/stomatitis, a viral exanthem, diarrhea, anosmia, and ageusia all point toward a viral cause instead.

Postinfectious complications — why treatment matters

Acute rheumatic fever (ARF)

A delayed autoimmune reaction to untreated or inadequately treated GAS pharyngitis, typically presenting 1–5 weeks later with migratory polyarthritis, carditis, chorea (Sydenham chorea), subcutaneous nodules, or erythema marginatum (the Jones criteria major manifestations). This is the principal reason GAS pharyngitis is treated with antibiotics at all.^[3]

Poststreptococcal glomerulonephritis (PSGN)

A delayed immune-complex nephritis presenting 1–3 weeks after pharyngitis (or after streptococcal skin infection) with dark or tea-coloured urine, edema, and hypertension. Unlike ARF, antibiotic treatment of the preceding pharyngitis has not been clearly shown to prevent PSGN.

PANDAS / PANS

Pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS) is a proposed subset of pediatric acute-onset neuropsychiatric syndrome (PANS) — abrupt-onset obsessive-compulsive symptoms or tics temporally linked to GAS infection in a prepubertal child. It remains a specialist (neurology/psychiatry/immunology) diagnosis of exclusion; routine GAS testing of children with new neuropsychiatric symptoms but no pharyngitis is not recommended.

Risk Factors

Factors that increase the likelihood the current sore throat is GAS

Age 5–15 years.
Close contact with a household member, classmate, or daycare contact with confirmed GAS pharyngitis, or a recognized outbreak setting.
Late autumn through spring (peak GAS circulation season).
Crowded living or care settings.

Factors that raise the stakes of a missed or delayed diagnosis (elevated ARF risk)

A personal history of prior acute rheumatic fever — these patients need antibiotics for essentially any confirmed GAS pharyngitis, since recurrent ARF risk after a further GAS infection is substantially higher than a first episode.
Indigenous ancestry, or residence in a First Nations, Inuit, or Métis community, reflecting well-documented systemic health-care access inequities that raise contemporary Canadian ARF incidence in these communities relative to the general population.
Residence in a household or community with a known elevated local ARF incidence, or in a developing-country setting.
Age 5–15 years is also the peak age range for a first ARF episode, independent of GAS-acquisition risk above.

Red Flags & Refer

Most GAS pharyngitis is uncomplicated, but escalate immediately for any of the following:

Drooling, stridor, muffled ("hot potato") voice, or trismus (difficulty opening the mouth) — suggests peritonsillar abscess, epiglottitis, or another deep neck space infection rather than uncomplicated pharyngitis.
Severe unilateral throat pain with uvular deviation toward the unaffected side and a bulging soft palate — classic peritonsillar abscess (quinsy) findings.
Stridor, tripod positioning, or acute respiratory distress in a child with sore throat and fever — treat as a possible airway emergency (epiglottitis) and do not examine the throat with a tongue depressor outside a controlled airway setting.
Neck stiffness, torticollis, or refusal to move the neck with drooling — possible retropharyngeal abscess.
Rigors, unilateral neck swelling or pain along the jaw/sternocleidomastoid, and signs of septic emboli (e.g., respiratory symptoms) following a recent sore throat — possible Lemierre syndrome (septic thrombophlebitis of the internal jugular vein), a rare but life-threatening complication requiring emergency imaging and prolonged intravenous antibiotics.
Inability to swallow secretions, significant drooling, or any sign of impending airway compromise in a child or adult.
Symptoms consistent with acute rheumatic fever — migratory joint pain/swelling, new murmur or chest symptoms, chorea, subcutaneous nodules, or erythema marginatum — arising weeks after a sore throat episode: refer urgently for cardiology assessment.
Symptoms consistent with poststreptococcal glomerulonephritis — dark or tea-coloured urine, new edema, or new hypertension arising 1–3 weeks after pharyngitis (or a streptococcal skin infection): refer urgently for assessment.

Assessment & Diagnosis

Differentiating GAS pharyngitis from its common mimics

Feature	GAS pharyngitis	Viral pharyngitis	Infectious mononucleosis (EBV)	Gonococcal pharyngitis
Typical context	School-age child/adolescent, late autumn-spring	Any age, any season, often with a concurrent household URI	Adolescents and young adults	Sexually active adult with orogenital exposure; often asymptomatic
Onset	Abrupt	Gradual, with a viral prodrome	Gradual, over several days	Variable; frequently mild or asymptomatic
Exudate	Common	Uncommon (adenovirus is an exception)	Common, often thick and extensive	Variable; may be entirely absent
Lymphadenopathy	Tender, anterior cervical	Mild, variable	Prominent, often posterior cervical or generalized, with splenomegaly	Localized cervical, variable
Distinguishing features	Scarlatiniform rash; absence of cough/rhinorrhea/conjunctivitis	Cough, rhinorrhea, conjunctivitis, hoarseness, oral ulcers, diarrhea	Marked fatigue, hepatosplenomegaly, palatal petechiae, periorbital edema; an ampicillin/amoxicillin-class rash is a well-known clue if given inappropriately	Concurrent genital, rectal, or ocular symptoms; history of oral-genital contact
Confirmatory test	RADT or throat culture	Clinical; viral PCR if the result would change management	Heterophile antibody (Monospot) and/or atypical lymphocytosis on blood smear; EBV serology if needed	N. gonorrhoeae NAAT — a routine GAS throat culture will not detect it, so gonococcal pharyngitis must be specifically suspected and tested for

GAS pharyngitis and infectious mononucleosis frequently coexist — a meaningful proportion of patients with mononucleosis also carry GAS in the oropharynx, so a positive GAS test in a patient with a mononucleosis-like presentation (marked fatigue, splenomegaly, posterior/generalized adenopathy) does not exclude mononucleosis and should not delay appropriate testing for it.

History

Characterize onset, duration (pharyngitis by definition is acute if under 2 weeks), and associated symptoms — specifically ask about cough, rhinorrhea, conjunctivitis, and diarrhea, since their presence argues for a viral cause.
Ask about known GAS exposure (household member, classmate, daycare contact) and any personal history of prior acute rheumatic fever.
Assess ARF-risk context: Indigenous ancestry, community ARF incidence, and recent travel/residence in a higher-incidence setting.
In a sexually active adolescent or adult, ask specifically about oral-genital contact — gonococcal pharyngitis will not be detected by a standard GAS test and needs its own specific testing.
Ask about systemic features suggesting a mononucleosis-like illness (marked fatigue, abdominal fullness/splenomegaly) rather than routine bacterial pharyngitis.

Pretest probability: the modified Centor (McIsaac) score

The modified Centor score — commonly called the McIsaac score after the investigator who added the age adjustment to the original Centor criteria — is a simple additive point-sum used to estimate the pretest probability that a patient's sore throat is due to GAS, and to decide who actually needs testing.^[4]

Criterion	Points
Temperature > 38°C	+1
Absence of cough	+1
Swollen, tender anterior cervical lymph nodes	+1
Tonsillar swelling or exudate	+1
Age 3-14 years	+1
Age 15-44 years	0
Age ≥ 45 years	-1

Total score	Approximate probability of GAS	Action
≤ 0	1-2.5%	No testing, no antibiotics
1	5-10%	No testing, no antibiotics
2	11-17%	Testing reasonable (RADT/culture)
3	28-35%	Testing recommended
4-5	51-53%	Testing recommended (do not skip straight to empiric antibiotics)

The 2025 IDSA guideline update reinforces using a validated clinical scoring system — the modified Centor/McIsaac score or an equivalent validated tool — specifically to identify low-probability patients (score ≤1) who do not need testing at all, while still recommending testing rather than empiric treatment even at higher scores; a high score raises pretest probability but is not itself a substitute for a positive RADT or culture.^[5] This score has not been validated for children under 3 years old.

Laboratory testing

Test	Key characteristics	Role
Rapid antigen detection test (RADT)	Result available within minutes. High specificity, so a positive result can be acted on directly without confirmation. Sensitivity is lower than culture.	First-line test in most settings given the fast turnaround.
Throat culture	Gold-standard sensitivity, but result takes roughly 24-48 hours. Allows antibiotic susceptibility testing when a beta-lactam alternative is needed.	Used to confirm a negative RADT when pretest probability is high (especially children/adolescents), or as the primary test if RADT is unavailable.
Serology (anti-streptolysin O, anti-DNase B titres)	Reflects past, not current, infection.	No role in acute diagnosis. Useful only retrospectively when investigating a suspected postinfectious complication (ARF, PSGN).

When to test

Test essentially all patients with a modified Centor/McIsaac score of 3-5, and any lower-scoring patient with an elevated personal ARF risk.

When not to test

Clinical features strongly favour a viral cause (especially with confirmatory viral testing available).
Modified Centor/McIsaac score of 0-1, particularly when ARF risk is low.
Post-treatment test-of-cure in an asymptomatic, appropriately treated patient.
Asymptomatic close contacts, outside a recognized outbreak investigation.
Children under 3 years old, without an atypical presentation or known household GAS exposure — GAS pharyngitis is uncommon and ARF is rare at this age.

Adults: a negative RADT (or an initial negative culture) is sufficient to routinely withhold antibiotics, given the low baseline ARF risk in adults. Children and adolescents (or any patient with a high pretest probability): if the RADT is negative, send a confirmatory throat culture and withhold antibiotics for 24-48 hours pending the result — this does not increase ARF risk and avoids unnecessary antibiotic exposure, since antibiotics started within 9 days of symptom onset still prevent ARF.^[1]

Treatment Targets

Confirm GAS as the actual cause before initiating antibiotics, rather than treating on symptoms alone.
Prevent the nonsuppurative complication of greatest concern — acute rheumatic fever — by treating confirmed cases within 9 days of symptom onset.
Prevent suppurative complications: peritonsillar abscess, acute otitis media, acute sinusitis, cervical lymphadenitis, and — rarely — bacteremia, meningitis, or necrotizing fasciitis.
Provide symptomatic relief of throat pain and fever.
Shorten the period of contagiousness and limit transmission to close contacts.
Avoid unnecessary antibiotic exposure in patients with a low pretest probability of GAS or a low personal risk of ARF.

Choose Initial Treatment

Direct treatment rule

Whether to test and treat at all

Do not treat based on symptoms or exam findings alone — a clinical diagnosis by itself should never trigger antibiotic prescribing. Use the modified Centor/McIsaac score to decide who needs testing, then treat only a positive rapid antigen detection test (RADT) or throat culture with the appropriate clinical picture.^[1]^[5]

Test (RADT and/or throat culture) essentially all patients with a modified Centor/McIsaac score of 3 or 4/5, and any patient with a lower score but an elevated personal ARF risk (prior ARF, Indigenous ancestry, or residence in a high-incidence community).

Do not routinely test or treat a patient with a score of 0 or 1, especially when clinical features already suggest a viral cause, or a child under 3 years old without a specific atypical presentation or known household GAS exposure — GAS pharyngitis and ARF are both rare in this age group.

Antibiotic choice

1st line, no penicillin allergy penicillin V or amoxicillin — amoxicillin is frequently preferred in children who need a liquid formulation. Narrow spectrum, low cost, and no documented GAS resistance make these the preferred choice over broader-spectrum agents even though several alternatives are equally effective microbiologically.^[1]

2nd line — use for a non-severe (non-IgE-mediated) penicillin allergy, e.g. a remote non-urticarial rash: a narrow-spectrum first-generation cephalosporin (cephalexin or cefadroxil). Avoid this option specifically when the prior reaction was anaphylaxis, urticaria, or another IgE-mediated pattern, given cross-reactivity risk.

Special situation — true IgE-mediated/anaphylactic penicillin allergy: clindamycin, or a macrolide (azithromycin or clarithromycin). These are reserved for genuine severe allergy rather than used as a routine alternative, because macrolide and clindamycin resistance in GAS — unlike penicillin, where resistance has never been documented — does occur and varies by region and over time; check local susceptibility data if one of these agents is being re-prescribed after apparent treatment failure.

Duration

Ten days of penicillin V or amoxicillin is the standard duration for essentially every patient, because a full 10-day course most reliably achieves pharyngeal eradication of GAS and rheumatic fever prevention — the evidence base for ARF prevention is built entirely on 10-day regimens. Do not shorten a penicillin/amoxicillin course to symptom-relief-only durations (5–7 days) when ARF prevention is a treatment goal, which it is for essentially every patient being treated.^[1]

Azithromycin's approved 5-day course is the one genuine exception — it is not a "shortened" regimen but its own standard duration, used specifically for penicillin-allergic patients. Clindamycin, cephalosporins, and clarithromycin are still given for the full 10 days.

Non-Pharmacologic Treatment

Adequate fluid intake, rest, and a soft diet during the acute illness.
Warm liquids (e.g., tea), cold items (ice chips, popsicles), or throat lozenges/hard candies may give modest symptomatic relief; medicated lozenges, sprays, and gargles are not clearly superior to these simple measures.
Hand hygiene and respiratory/cough etiquette to limit transmission to household and close contacts.
A patient started on an appropriate antibiotic is generally considered noncontagious, and safe to return to school, daycare, or work, after roughly 24 hours of treatment and once significantly improved/afebrile — confirm against current local public-health guidance.
GAS pharyngeal carriers (positive test but no true acute infection) are not treated and pose low transmission and complication risk — routine treatment of chronic carriage is not recommended.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
Penicillin V Preferred	1st-line therapy, no penicillin allergy	Adults/children ≥27 kg: 250 mg PO QID or 500 mg PO BID x 10 days. Children under 27 kg: 250 mg PO BID-TID x 10 days	GI upset, rare hypersensitivity	Drug of choice. No documented GAS resistance to penicillin, ever.
Amoxicillin Preferred	1st-line therapy, especially when a liquid formulation is needed	500 mg PO TID (or 1000 mg PO once daily) x 10 days. Children: 50 mg/kg PO once daily (max 1000 mg) or 25 mg/kg PO BID (max 500 mg/dose) x 10 days	GI upset, rash (including non-allergic ampicillin-class rash with concurrent EBV infection)	Preferred in children needing a suspension. Once-daily dosing supports adherence.
Cephalexin Alternative	2nd line — non-severe (non-IgE) penicillin allergy	500 mg PO BID x 10 days. Children: 20 mg/kg/dose PO BID (max 500 mg/dose) x 10 days	GI upset, rash	Avoid if the prior penicillin reaction was anaphylaxis/urticaria/angioedema.
Cefadroxil Alternative	2nd line — non-severe (non-IgE) penicillin allergy	1 g PO once daily (or divided BID) x 10 days. Children: 30 mg/kg PO once daily (max 1 g) x 10 days	GI upset, rash	Once-daily option; avoid if the prior penicillin reaction was IgE-mediated.
Clindamycin Special situation	True IgE-mediated/anaphylactic penicillin allergy; also an option for recurrent/relapsing pharyngitis	300 mg PO TID x 10 days. Children: 7 mg/kg/dose PO TID (max 300 mg/dose) x 10 days	Diarrhea, C. difficile-associated colitis	Check local resistance data before re-prescribing after a treatment failure.
Azithromycin Special situation	True IgE-mediated/anaphylactic penicillin allergy	500 mg PO on day 1, then 250 mg PO once daily for 4 more days (5 days total). Children: 12 mg/kg PO once daily x 5 days (max 500 mg/day)	GI upset, QTc prolongation	5-day course is the approved duration for this agent, not a shortened one. Fewer drug interactions than clarithromycin.
Clarithromycin Special situation	True IgE-mediated/anaphylactic penicillin allergy	250 mg PO BID x 10 days. Children: 7.5 mg/kg/dose PO BID (max 250 mg/dose) x 10 days	GI upset, QTc prolongation	More CYP3A4 drug-interaction potential than azithromycin — review the patient's other medications.
Acetaminophen Preferred	Symptomatic relief of throat pain and fever, all patients	650-1000 mg PO Q4-6H PRN (max per product labelling). Children: weight-based per product labelling	Hepatotoxicity in overdose	Equivalent efficacy to ibuprofen for pain/fever in this setting; choose based on patient factors.
Ibuprofen Preferred	Symptomatic relief of throat pain and fever, all patients	400 mg PO Q6-8H PRN with food. Children: weight-based per product labelling	GI upset, rare renal effects	Avoid in significant renal impairment, dehydration, or peptic ulcer disease.
Dexamethasone Special situation	Adjunct for severe pain only, case-by-case	Single dose 10 mg PO/IM (adult). Children: single dose 0.6 mg/kg PO/IM (max 10 mg)	Rare with a single dose; standard steroid precautions apply	Not routinely recommended — the benefit over analgesics alone is modest. Use shared decision-making, not as default therapy.

Not recommended, despite apparent in-vitro susceptibility: trimethoprim-sulfamethoxazole, tetracyclines, and fluoroquinolones do not reliably eradicate GAS from the pharynx and are not appropriate choices for this indication regardless of reported susceptibility on a culture report.^[1]

On dexamethasone specifically: a single adjunctive dose modestly speeds pain resolution on top of standard analgesia (with or without antibiotics), but guidelines stop short of a routine recommendation given the small effect size and the confounding effect of concurrent antibiotics — use shared decision-making for a patient with severe pain rather than defaulting to it.^[6]

Special Populations

Pregnancy

Diagnosis and testing thresholds are unchanged in pregnancy. Penicillin V, amoxicillin, and cephalosporins (cephalexin, cefadroxil) are all considered safe throughout pregnancy and remain first-line. For a true penicillin allergy in pregnancy, azithromycin or clindamycin can be used.

Breastfeeding

Penicillin V, amoxicillin, cephalosporins, and macrolides (azithromycin, clarithromycin) are all considered compatible with breastfeeding. Clindamycin is also an option; monitor the breastfed infant for possible gastrointestinal effects (diarrhea, candidiasis) from altered infant gut flora.

Pediatrics

GAS pharyngitis and ARF are both genuinely rare under age 3 — testing is generally not indicated in this age group outside a specific atypical presentation or known household exposure. Amoxicillin suspension is frequently preferred over penicillin V suspension for palatability and once-daily/BID dosing convenience. Benzathine penicillin G (see Drug Tables) is a reasonable single-dose IM alternative when oral adherence for a full 10-day course is a genuine concern.

Renal and hepatic impairment

Penicillins and cephalosporins are renally cleared and require dose-interval adjustment in significant renal impairment — confirm against current renal dosing references for the specific agent and degree of impairment. Clindamycin, azithromycin, and clarithromycin do not require routine renal adjustment but clarithromycin needs dose reduction in significant renal impairment specifically; hepatic impairment warrants caution with macrolides given hepatic metabolism.

Asymptomatic GAS carriers

A positive test in an asymptomatic patient (chronic pharyngeal carriage) is not an indication for antibiotic treatment in any population — carriers have low risk of both complications and transmission, and treatment does not reliably eradicate carriage.

Monitoring & Follow-Up

Expect noticeable symptomatic improvement within 24–48 hours of starting an appropriate antibiotic; fever typically resolves within this window as well. If there is no improvement by 48–72 hours, reassess rather than simply waiting out the full course (see Treatment Failure). Routine test-of-cure after completing therapy is not needed in an asymptomatic patient who has responded appropriately. For patients in an elevated-ARF-risk group (prior ARF, Indigenous ancestry, high-incidence community), explicitly counsel on the delayed symptoms of rheumatic fever (joint pain/swelling, new murmur or chest symptoms, chorea, subcutaneous nodules, rash) and of poststreptococcal glomerulonephritis (dark urine, swelling, high blood pressure) to watch for over the following 1–5 weeks, since these complications present well after the pharyngitis itself has resolved. During the acute illness, monitor specifically for worsening unilateral throat pain, new trismus, or drooling, which suggest an evolving peritonsillar abscess rather than expected slow improvement.

Treatment Failure / Next Step

Confirm the full antibiotic course was actually taken at the correct dose, route, and duration — nonadherence is the most common cause of apparent treatment failure.
Reconsider whether the original diagnosis was actually confirmed by a positive RADT or culture, or whether treatment was started empirically on symptoms alone; if the latter, retest before assuming drug failure.
Consider an alternative or coexisting diagnosis: viral pharyngitis with incidental GAS colonization, infectious mononucleosis, gonococcal pharyngitis in a sexually active patient, or an evolving suppurative complication (peritonsillar abscess) — see the differential table in Assessment & Diagnosis.
If GAS relapse is genuinely confirmed after an adequately taken penicillin course, do not switch antibiotic class assuming penicillin resistance — GAS resistance to penicillin has never been documented. Consider incomplete oropharyngeal eradication, a new reinfection from an untreated household contact, or intercurrent viral illness misread as relapse.^[1]
For a symptomatic patient with genuinely recurrent, culture-confirmed episodes (multiple discrete episodes rather than persistent carriage with intercurrent viral illnesses), specialist-directed options include clindamycin, amoxicillin-clavulanate, or combined penicillin plus rifampin to address possible copathogens or intracellular GAS reservoirs — these are not routine first-choice regimens.
Refer to otolaryngology for consideration of tonsillectomy when recurrent tonsillitis meets a validated frequency threshold: ≥7 episodes in the past year, ≥5 episodes per year for 2 consecutive years, or ≥3 episodes per year for 3 consecutive years, with each episode adequately documented (sore throat plus at least one of fever, tender cervical adenopathy, tonsillar exudate, or a positive GAS test). At least 12 months of watchful observation is reasonable before referral in a patient without other modifying factors; antibiotic allergy/intolerance, PFAPA syndrome, or a history of peritonsillar abscess can justify earlier referral.^[7]

Common Errors to Avoid

Diagnosing and treating GAS pharyngitis on symptoms or exam findings alone, without a positive RADT or throat culture.
Shortening a penicillin or amoxicillin course below 10 days when rheumatic fever prevention is a treatment goal — which it is for nearly every patient being treated.
Prescribing trimethoprim-sulfamethoxazole, a tetracycline, or a fluoroquinolone for GAS pharyngitis — these do not reliably eradicate GAS from the pharynx regardless of apparent in-vitro susceptibility.
Treating an asymptomatic GAS carrier or an asymptomatic close contact without symptoms.
Switching antibiotic class after an apparent treatment failure on the assumption of penicillin resistance, which has never been documented for GAS.
Defaulting to a macrolide or clindamycin as the routine penicillin-allergy alternative without first establishing whether the prior reaction was actually IgE-mediated — narrow-spectrum cephalosporins are appropriate, preferred, and lower-resistance-risk for most non-severe reactions.
Missing red-flag features of peritonsillar abscess, epiglottitis, or Lemierre syndrome by treating every sore throat as routine, uncomplicated pharyngitis.
Relying on a negative RADT alone to exclude infection in a child or adolescent (or any high-ARF-risk patient) instead of sending a confirmatory throat culture.
Testing or treating a child under 3 years old for routine sore throat without an atypical presentation or known GAS exposure — both GAS pharyngitis and ARF are rare in this age group.

Clinical Decision Algorithm

Assessment and testing decision

Acute sore throat (under 2 weeks duration)

Screen for red flags: drooling, stridor, trismus, muffled voice, neck stiffness, or signs of Lemierre syndrome

Red flags present

Escalate emergently — possible peritonsillar/retropharyngeal abscess, epiglottitis, or Lemierre syndrome

No red flags

Calculate the modified Centor/McIsaac score and assess for viral features (cough, rhinorrhea, conjunctivitis, diarrhea)

Score 0-1, and/or viral features present, and low personal ARF risk

No testing, no antibiotics — supportive care and analgesia

Score 2-5, or elevated personal ARF risk regardless of score

Obtain RADT (± confirmatory throat culture) — proceed to the testing algorithm below

Test result to treatment

RADT obtained

RADT positive

Treat as confirmed GAS pharyngitis: penicillin V or amoxicillin x 10 days (see allergy pathway below)

RADT negative — adult, low ARF risk

Withhold antibiotics; no further routine testing needed

RADT negative — child/adolescent or elevated ARF risk

Send confirmatory throat culture; withhold antibiotics 24-48h pending result (antibiotics within 9 days of onset still prevent ARF)

Culture positive

Treat: penicillin V or amoxicillin x 10 days

Culture negative

No treatment; reassess if symptoms worsen or fail to resolve

Choice of antibiotic by penicillin-allergy status

Confirmed GAS pharyngitis requiring treatment

No penicillin allergy

Penicillin V or amoxicillin x 10 days

Non-severe (non-IgE) penicillin allergy

Cephalexin or cefadroxil x 10 days

Severe IgE-mediated/anaphylactic penicillin allergy

Clindamycin x 10 days, or azithromycin x 5 days, or clarithromycin x 10 days — check local resistance data if re-prescribing after failure

Drug Tables

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Penicillins (1st line, no penicillin allergy)

No documented GAS resistance to penicillin has ever occurred — these remain preferred over broader-spectrum alternatives.

Drug	Dosage	Adverse effects	Comments
Penicillin V	Adults / children ≥27 kg: 250 mg PO QID or 500 mg PO BID x 10 days Children under 27 kg: 250 mg PO BID-TID x 10 days	GI upset, nausea, vomiting, diarrhea, rash, rare hypersensitivity	Oral route preferred over benzathine penicillin G IM given equal efficacy and less discomfort.
Amoxicillin	Adults: 500 mg PO TID x 10 days, or 1000 mg PO once daily x 10 days Children: 50 mg/kg PO once daily (max 1000 mg) x 10 days, or 25 mg/kg PO BID (max 500 mg/dose) x 10 days	GI upset, nausea, vomiting, diarrhea, rash (including a non-allergic rash if given during undiagnosed EBV mononucleosis)	Often preferred in children needing a liquid formulation; once-daily dosing option supports adherence.
Penicillin G benzathine	Adults / children ≥27 kg: 1,200,000 units IM as a single dose Children under 27 kg: 600,000 units IM as a single dose	Injection-site pain, rare hypersensitivity	Single IM dose ensures completion of therapy when adherence to a 10-day oral course is a genuine concern, or when oral intake is not tolerated.

Cephalosporins (2nd line — non-severe, non-IgE-mediated penicillin allergy)

Avoid this class specifically when the prior penicillin reaction was anaphylaxis, urticaria, or another IgE-mediated pattern given cross-reactivity risk; otherwise a reasonable option after treatment failure with penicillin or in nonimmediate penicillin hypersensitivity.

Drug	Dosage	Adverse effects	Comments
Cephalexin	Adults: 500 mg PO BID x 10 days Children: 20 mg/kg/dose PO BID (max 500 mg/dose) x 10 days	GI upset, nausea, vomiting, diarrhea, rash	Available as a suspension for pediatric use.
Cefadroxil	Adults: 1 g PO once daily, or divided BID, x 10 days Children: 30 mg/kg PO once daily (max 1 g) x 10 days	GI upset, nausea, vomiting, diarrhea, rash	Once-daily dosing may support adherence over cephalexin's twice-daily regimen.

Lincosamides (severe/IgE-mediated penicillin allergy)

An alternative for true penicillin-allergic patients, and also an option for symptomatic patients with genuinely recurrent, culture-confirmed pharyngitis episodes under specialist direction.

Drug	Dosage	Adverse effects	Comments
Clindamycin	Adults: 300 mg PO TID x 10 days Children: 7 mg/kg/dose PO TID (max 300 mg/dose) x 10 days; maximum 900 mg/day	Diarrhea (common), Clostridioides difficile colitis (may occur with any antibiotic but is particularly associated with clindamycin)	Check local resistance data before re-prescribing after an apparent treatment failure, given rising resistance in some regions.

Macrolides (severe/IgE-mediated penicillin allergy)

Alternatives for true penicillin-allergic patients. Macrolide resistance in GAS — unlike penicillin — does occur and varies geographically and over time; these are reserved for genuine allergy rather than used as a routine substitute.

Drug	Dosage	Adverse effects	Comments
Azithromycin	Adults: 500 mg PO on day 1, then 250 mg PO once daily x 4 more days (5 days total) Children: 12 mg/kg PO once daily x 5 days (max 500 mg/day)	GI upset, nausea, vomiting, diarrhea, rash, QTc-interval prolongation	The 5-day course is azithromycin's own approved regimen, not a shortened one. Fewer drug interactions than clarithromycin.
Clarithromycin	Adults: 250 mg PO BID x 10 days Children: 7.5 mg/kg/dose PO BID (max 250 mg/dose) x 10 days; maximum 500 mg/day	GI upset, nausea, vomiting, diarrhea, rash, QTc-interval prolongation	More CYP3A4 drug-interaction potential than azithromycin (e.g., increased levels of atorvastatin, carbamazepine, digoxin, simvastatin) — review the patient's other medications before prescribing.

Analgesics and antipyretics

For symptomatic relief in every patient, regardless of whether antibiotics are also indicated — analgesia is not conditional on a positive GAS test.

Drug	Dosage	Adverse effects	Comments
Acetaminophen	Adults: 650-1000 mg PO Q4-6H PRN, per product maximum daily dose Children: Weight-based dosing per current product labelling	Hepatotoxicity in overdose	Equivalent efficacy to ibuprofen for throat pain and fever in this setting.
Ibuprofen	Adults: 400 mg PO Q6-8H PRN with food Children: Weight-based dosing per current product labelling	GI upset, rare renal effects	Avoid in significant renal impairment, dehydration, or active peptic ulcer disease.

Adjunctive corticosteroid (special situation only)

Not routinely recommended given the modest benefit magnitude and the confounding effect of concurrent antibiotics on pain relief — reserve for case-by-case use in severe pain after a patient-centred discussion.

Drug	Dosage	Adverse effects	Comments
Dexamethasone	Adults: 10 mg PO or IM as a single dose Children: 0.6 mg/kg PO or IM as a single dose (max 10 mg)	Uncommon with a single dose; standard corticosteroid precautions apply	May modestly shorten time to symptom resolution when added to standard analgesia, with or without concurrent antibiotics.

References

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Antibiotics for treatment of sore throat in children and adults — Cochrane Database of Systematic Reviews (Spinks A, Glasziou PP, Del Mar CB). Cochrane Database Syst Rev 2021;12:CD000023
Revision of the Jones Criteria for the Diagnosis of Acute Rheumatic Fever in the Era of Doppler Echocardiography: A Scientific Statement from the American Heart Association — Circulation, American Heart Association (Gewitz MH, Baltimore RS, Tani LY, et al.). Circulation 2015;131(20):1806-1818
A clinical score to reduce unnecessary antibiotic use in patients with sore throat — Canadian Medical Association Journal (McIsaac WJ, White D, Tannenbaum D, Low DE). CMAJ 1998;158(1):75-83
2025 Clinical Practice Guideline Update by the Infectious Diseases Society of America on Group A Streptococcal Pharyngitis: Risk Assessment Using Clinical Scoring Systems in Children and Adults — Clinical Infectious Diseases, Infectious Diseases Society of America (Barshak MB, Linder JA, Watson ME Jr, Wessels MR, et al.). Clin Infect Dis 2025;ciaf668
Corticosteroids for treatment of sore throat: systematic review and meta-analysis of randomised trials — BMJ (Sadeghirad B, Siemieniuk RAC, Brignardello-Petersen R, et al.). BMJ 2017;358:j3887
Clinical Practice Guideline: Tonsillectomy in Children (Update) — Otolaryngology-Head and Neck Surgery, American Academy of Otolaryngology-Head and Neck Surgery Foundation (Mitchell RB, Archer SM, Ishman SL, et al.). Otolaryngol Head Neck Surg 2019;160(1_suppl):S1-S42

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.