Best Antibiotic for a Sore Throat or Tonsillitis (and Why Not Amoxicillin)
A full comparison of the antibiotics used for bacterial throat infection in the UK, and the specific reason amoxicillin is not first choice.
Part of our Sore Throat condition guide.
Key fact: The best antibiotic for a sore throat is the narrowest one that works — phenoxymethylpenicillin. Broader is not stronger, and amoxicillin is specifically avoided because of the rash it causes in glandular fever.
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View Sore Throat Treatments →The short answer
For a bacterial sore throat or tonsillitis in the UK, the best antibiotic is phenoxymethylpenicillin (penicillin V). If you cannot take penicillin, it is clarithromycin. In pregnancy with a penicillin allergy, it is erythromycin.
Amoxicillin, which many people expect and some request by name, is deliberately not first choice — for a specific and well-documented reason covered below.
Penicillin V
UK first choice for bacterial sore throat
80+ yrs
without meaningful strep resistance to penicillin
~70%
of sore throats need no antibiotic at all
Full antibiotic comparison table
| Antibiotic | UK position | Adult dose | Course | Key consideration |
|---|---|---|---|---|
| Phenoxymethylpenicillin | First choice | 500mg four times daily, or 1g twice daily | 5–10 days | Narrow spectrum, no strep resistance. Must be taken on an empty stomach. |
| Clarithromycin | Alternative first choice | 250–500mg twice daily | 5 days | For penicillin allergy. Many drug interactions. |
| Erythromycin | Alternative in pregnancy | 250–500mg four times daily | 5 days | Preferred macrolide in pregnancy. More gut upset than clarithromycin. |
| Amoxicillin | Not recommended first line | — | — | Causes widespread rash in glandular fever. Broader than necessary. |
| Co-amoxiclav | Not routine | — | — | Much broader spectrum, reserved for complications. Higher risk of gut side effects. |
| Azithromycin | Not routine in UK sore throat guidance | — | — | Higher macrolide resistance pressure. Used more in other countries. |
| Cephalexin and other cephalosporins | Not routine | — | — | Broader than needed. Reserved for specific circumstances. |
| Doxycycline | Not used | — | — | Poor activity against group A Streptococcus. |
Why phenoxymethylpenicillin is first choice
No meaningful resistance
Group A Streptococcus remains uniformly sensitive to penicillin after more than eight decades of clinical use. Almost nothing else in medicine can claim that.
Narrow spectrum
It hits the target organism and spares much of the rest, which means less disruption to your gut and less pressure driving resistance.
No glandular fever rash
Unlike the aminopenicillins, it does not trigger the widespread rash seen when infectious mononucleosis is treated.
Extensive safety record
Decades of data across all ages, including pregnancy and breastfeeding.
Few interactions
Unlike clarithromycin, it interacts with very little, which simplifies prescribing for people on multiple medicines.
Inexpensive
A cheap generic, which matters when prescribed at population scale.
The main drawback is practical rather than clinical: it must be taken on an empty stomach, and the four-times-daily schedule is demanding. The 1g twice-daily option exists partly to address this. Full detail is in our guide to phenoxymethylpenicillin for sore throat.
Why amoxicillin is not used for sore throat
Amoxicillin is one of the most familiar antibiotics in the UK, and people often assume it is the obvious choice for a throat infection. It is not, and the reasoning is worth understanding.
To be clear on one point: amoxicillin does work against group A Streptococcus. It is not ineffective. The problem is a specific and avoidable harm.
The problem in one sentence
Glandular fever produces a severe tonsillitis that can be clinically indistinguishable from strep throat, and giving amoxicillin to someone with glandular fever causes a widespread itchy rash in a large proportion of cases.
Why that matters more than it sounds
- The rash is uncomfortable, extensive and can last one to two weeks
- It is not a true penicillin allergy, but it is very frequently recorded as one
- That inaccurate label then follows the person for life, pushing them towards broader, less effective and more expensive antibiotics with worse average outcomes
- The people most likely to have glandular fever — teenagers and young adults — are exactly the group most likely to present with severe tonsillitis
Set against that, amoxicillin offers no clinical advantage over penicillin V for this infection. It is broader spectrum, which is a disadvantage rather than a benefit here. So the risk is taken for no gain, which is why UK guidance simply avoids it.
The glandular fever rash, explained
The mechanism is an immune interaction rather than an allergy. During Epstein-Barr virus infection the immune system is in a highly activated state, and this appears to drive a transient hypersensitivity response to aminopenicillins — amoxicillin and ampicillin specifically.
The rash is typically widespread, red, blotchy and itchy, appearing several days into the course and covering the trunk and limbs. It resolves without lasting harm.
If this has happened to you: a rash that occurred while taking amoxicillin during a glandular fever illness is not proof of penicillin allergy. It is worth raising with your GP, because formal allergy assessment may allow an inaccurate label to be removed. More than 90 per cent of people carrying a penicillin allergy label are found not to be allergic on testing.
Clarithromycin: the penicillin-allergy option
Where penicillin genuinely cannot be used, clarithromycin is the UK alternative first choice at 250mg to 500mg twice daily for 5 days in adults.
It is a good antibiotic with two practical advantages over penicillin V: twice-daily dosing rather than four times, and no requirement to take it on an empty stomach. It also has two significant disadvantages: macrolide resistance in streptococci does occur, unlike penicillin resistance, and clarithromycin interacts with a long list of common medicines including statins, warfarin and several heart drugs.
That interaction profile is the main reason it stays second rather than first. Our clarithromycin for sore throat guide covers the interactions in full.
Is a stronger antibiotic better?
This is one of the most persistent misconceptions in primary care, and it is worth addressing directly.
"Stronger" is not really a property antibiotics have. What they have is spectrum — the range of bacteria they act against — and activity against particular organisms. A broad-spectrum antibiotic is not more powerful against streptococcus than a narrow one that streptococcus happens to be highly sensitive to.
| Assumption | Reality |
|---|---|
| Broader spectrum means more effective | Only if the target organism is resistant to the narrow option. Strep is not resistant to penicillin. |
| A bad sore throat needs a stronger drug | Severity reflects your immune response, not bacterial invincibility. The organism is the same. |
| Newer antibiotics work better | Newer usually means designed for resistant organisms elsewhere. It is not an upgrade here. |
| A broader antibiotic covers all bases | It also kills more of your normal bacteria, causing more side effects and more resistance. |
Pregnancy, children and special situations
| Situation | Preferred antibiotic | Note |
|---|---|---|
| Pregnancy, no allergy | Phenoxymethylpenicillin | Extensive safety data. Remains first choice. |
| Pregnancy, penicillin allergy | Erythromycin | Preferred over clarithromycin in pregnancy. |
| Breastfeeding | Phenoxymethylpenicillin | Usually considered compatible. Discuss with your prescriber. |
| Children | Phenoxymethylpenicillin, dosed by age | Oral solution available. Requires in-person assessment. |
| Scarlet fever | Phenoxymethylpenicillin | Full 10-day course rather than 5. |
| Genuine penicillin allergy | Clarithromycin | Full medicine list needed to check interactions. |
| Suspected quinsy | Urgent hospital assessment | Not a routine outpatient antibiotic decision. |
Children need in-person assessment. Access Doctor's online sore throat service is for adults. A child with suspected bacterial throat infection should be seen by a GP, NHS 111 or urgent care where they can be examined.
When the best antibiotic is none at all
For roughly 70 per cent of adult sore throats, the honest answer to "which antibiotic is best?" is "none". Viral infections do not respond to any antibiotic, and even bacterial sore throats are largely self-limiting.
UK guidance uses the FeverPAIN score to decide. A score of 0 to 1 means no antibiotic; 2 to 3 means a back-up prescription at most; 4 to 5 means an immediate antibiotic is reasonable. Our guide on antibiotics for sore throat walks through the whole decision, and sore throat vs strep throat covers how to score yourself.
How to get the right antibiotic in the UK
All oral antibiotics are prescription-only in the UK. There is no legal over-the-counter route, and any site selling antibiotics without an assessment should be avoided.
Legitimate routes are your GP practice, a community pharmacy offering NHS Pharmacy First in England, or a regulated online pharmacy prescribing after clinical consultation.
Order Penicillin V or Clarithromycin Online
Complete a short online consultation and a GPhC-registered pharmacist independent prescriber will assess whether an antibiotic is appropriate and which one suits your allergy history and medicines. Dispensed from our UK pharmacy and delivered discreetly, with no GP appointment needed.
Order Phenoxymethylpenicillin →Frequently Asked Questions
What is the best antibiotic for a sore throat?
Phenoxymethylpenicillin, also called penicillin V, is the best first-choice antibiotic for bacterial sore throat in the UK. Group A Streptococcus has never developed meaningful resistance to it, it has a narrow spectrum that disturbs the gut less than broader antibiotics, and it avoids the rash problem associated with amoxicillin. Adults take 500mg four times a day or 1000mg twice a day for 5 to 10 days. Clarithromycin is the recommended alternative for people with penicillin allergy.
Why is amoxicillin not used for sore throat?
Because a sore throat caused by glandular fever can look almost identical to strep throat, and giving amoxicillin to someone with glandular fever causes a widespread itchy rash in a large proportion of cases. That rash is not a true penicillin allergy, but it is frequently recorded as one, which then restricts that person's antibiotic options for life. Amoxicillin is also broader spectrum than necessary, so it disturbs more of the body's normal bacteria without offering better results against streptococcus.
Can I take amoxicillin for tonsillitis?
Amoxicillin does work against group A Streptococcus, so it is effective in the narrow sense, but UK guidance does not recommend it as first choice for tonsillitis. The reason is the risk of a widespread rash if the tonsillitis turns out to be glandular fever, which is common in exactly the teenage and young adult group most likely to present with severe tonsillitis. Phenoxymethylpenicillin achieves the same result without that risk, which is why it is preferred.
Which antibiotic is best for tonsillitis?
The same as for bacterial sore throat generally: phenoxymethylpenicillin first, at 500mg four times daily or 1000mg twice daily for 5 to 10 days in adults. Tonsillitis is not treated differently from other bacterial throat infections in UK guidance, because the organism responsible is usually the same. Clarithromycin is used where penicillin cannot be given, and erythromycin is preferred in pregnancy.
Is a stronger antibiotic better for a bad sore throat?
No. Broader spectrum does not mean stronger or more effective for this infection. Group A Streptococcus is highly sensitive to narrow-spectrum penicillin, so a broader antibiotic offers no additional benefit against it while causing more disruption to your normal bacteria, more side effects and more resistance pressure. Matching the antibiotic to the organism is what makes treatment effective, not reaching for something broader.
What antibiotic is used for sore throat in pregnancy?
Phenoxymethylpenicillin is generally considered suitable in pregnancy and remains first choice where a bacterial sore throat needs treating. If you have a penicillin allergy, erythromycin is preferred over clarithromycin during pregnancy because there is more reassurance data for it. Always tell your prescriber if you are pregnant, might be pregnant or are breastfeeding, so the antibiotic choice can be made appropriately.
How long does an antibiotic course for sore throat last?
Phenoxymethylpenicillin is prescribed for 5 to 10 days, with a full 10 days used where scarlet fever is diagnosed. Clarithromycin and erythromycin courses for sore throat are 5 days. You will typically feel substantially better after two or three days, but the course should be completed as prescribed, since stopping early risks the infection returning and leaves behind the hardest bacteria to kill.
Completing the treatment
The right antibiotic treats the infection, but pain relief is what gets you through the first 48 hours. Access Doctor supplies both after a short online consultation reviewed by a GPhC-registered pharmacist independent prescriber, dispensed from our UK pharmacy with no GP appointment needed. See the full range on the sore throat treatment page.
Antibiotic · Rx
Phenoxymethylpenicillin 250mg
The UK first-choice antibiotic for bacterial sore throat and tonsillitis.
View product →Antibiotic · Rx
Clarithromycin 500mg
The alternative where there is a genuine penicillin allergy.
View product →Pain relief · P
Difflam Sore Throat Spray
Benzydamine spray for the first days before the antibiotic takes effect.
View product →Pain relief · P
Difflam Oral Rinse
Benzydamine gargle covering the throat more widely than a spray.
View product →References
- National Institute for Health and Care Excellence. Sore throat (acute): antimicrobial prescribing (NG84). 2018, updated. nice.org.uk
- Joint Formulary Committee. British National Formulary: phenoxymethylpenicillin. bnf.nice.org.uk
- Joint Formulary Committee. British National Formulary: amoxicillin. bnf.nice.org.uk
- Joint Formulary Committee. British National Formulary: clarithromycin. bnf.nice.org.uk
- NHS. Glandular fever. nhs.uk
- NICE. Drug allergy: diagnosis and management (CG183). nice.org.uk
- NICE Clinical Knowledge Summaries. Sore throat – acute. cks.nice.org.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.