Amoxicillin vs Doxycycline for Sinusitis: Which Antibiotic and Why
A direct comparison—and why UK guidance doesn't start with either of them.
Part of our Sinusitis condition guide.
The headline: Neither is the UK first choice. NICE NG79 recommends phenoxymethylpenicillin first-line for acute sinusitis, with doxycycline as the main alternative for adults who can't take penicillin. Amoxicillin is standard in the United States, which is why so much online advice recommends it.
Sinusitis Assessed Online
Which antibiotic is appropriate—or whether one is needed at all—is a prescribing decision. Access Doctor's GPhC-registered pharmacist independent prescribers assess adults online and decide accordingly.
View Sinusitis Treatments →The comparison at a glance
| Amoxicillin | Doxycycline | |
|---|---|---|
| Class | Broad-spectrum penicillin | Tetracycline |
| UK position for sinusitis | Not first-line—phenoxymethylpenicillin is preferred | Main alternative where penicillin can't be used |
| US position | Standard first-line | Alternative |
| Doses per day | Three | One, after a first-day loading dose |
| Safe in penicillin allergy | No | Yes—unrelated class |
| Safe in pregnancy | Generally yes, on advice | No |
| Under 12 | Yes, weight-based | No |
| Take with food? | Either | With food and a full glass of water, sitting upright |
| Sun sensitivity | No | Yes—a genuine practical issue |
| Commonest side effects | Diarrhoea, nausea, thrush, rash | Nausea, sun sensitivity, throat irritation |
Why UK and US advice differ
If you search for sinusitis antibiotics, most of what you find recommends amoxicillin, often with clavulanic acid. That's American guidance, and it doesn't reflect UK practice.
UK guidance favours the narrowest antibiotic likely to work. Phenoxymethylpenicillin targets the likely organisms while doing less collateral damage to the rest of the bacteria you carry—which reduces both side effects and the pressure driving antibiotic resistance. That principle underpins NICE NG79.
Amoxicillin is a broader-spectrum penicillin. It's a perfectly good antibiotic, and it's used in UK practice in specific situations, but for uncomplicated acute sinusitis it's broader than the situation calls for. Our guide on penicillin for a sinus infection covers why the narrower option is preferred.
A practical consequence: if a US-based site tells you amoxicillin is what you need, don't go looking for it. A UK prescriber following NICE will offer something different, and that's not them getting it wrong.
Spectrum: what each one covers
The bacteria that cause acute bacterial sinusitis are predictable—principally Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Both antibiotics have activity against these, which is why both appear in guidelines internationally.
| Organism | Amoxicillin | Doxycycline |
|---|---|---|
| Streptococcus pneumoniae | Good | Good |
| Haemophilus influenzae | Good, though some strains produce beta-lactamase | Good |
| Moraxella catarrhalis | Often resistant—most strains produce beta-lactamase | Good |
| Atypical organisms | No activity | Some activity |
Beta-lactamase is an enzyme some bacteria produce that breaks penicillins down. It's why amoxicillin is sometimes combined with clavulanic acid, which blocks the enzyme. Doxycycline works by a completely different mechanism and is unaffected by it.
Does that make doxycycline the better antibiotic? No. In practice, sinusitis that reaches the point of needing antibiotics responds to either, and trials don't show a clear winner. Laboratory spectrum and clinical outcome aren't the same thing.
Dosing and practicality
This is where the two genuinely differ in a way you'll notice.
| Amoxicillin | Doxycycline | Phenoxymethylpenicillin | |
|---|---|---|---|
| Frequency | Three times a day | Once a day after day one | Four times a day |
| Timing relative to food | Flexible | With food, upright, full glass of water | On an empty stomach |
| Typical course for sinusitis | 5–7 days | 5–7 days | 5 days |
| Ease of sticking to it | Moderate | Easiest | Hardest |
Missed doses are the most common reason a course fails. A once-daily antibiotic that gets taken beats a theoretically ideal one that gets forgotten twice. Prescribers weigh this, particularly for people with irregular schedules or shift work.
Full dosing detail for doxycycline in sinusitis, including what to do about a missed dose, is in our penicillin allergy and sinusitis antibiotics guide.
Side effects compared
| Effect | Amoxicillin | Doxycycline |
|---|---|---|
| Diarrhoea | Common | Less common |
| Nausea | Common | Common |
| Thrush | Common | Less common |
| Rash | Possible—can indicate allergy | Uncommon |
| Sensitivity to sunlight | No | Yes—burns far more easily |
| Oesophageal irritation | No | Yes if taken lying down or dry |
| Serious allergic reaction | Rare but recognised | Rare |
The sun sensitivity with doxycycline isn't a minor footnote. People burn in conditions that would normally be harmless, including through cloud and in the UK. If you're taking it, use high-factor sunscreen, cover up and avoid sunbeds for the duration of the course.
Stop and seek urgent help for swelling of the face, lips or tongue, difficulty breathing, a widespread rash with blistering, or severe or bloody diarrhoea. These apply to any antibiotic.
Interactions and food
Doxycycline has more of these, and they're easy to trip over unintentionally.
- Indigestion remedies, calcium, iron and magnesium bind to doxycycline and stop it being absorbed. Separate them by at least two hours.
- Dairy can reduce absorption for the same reason, so avoid taking it with a large glass of milk.
- Warfarin—doxycycline can increase its effect, so INR monitoring may be needed.
- Take it sitting or standing with a full glass of water, and stay upright for half an hour. Doxycycline stuck in the gullet causes painful irritation.
Amoxicillin is simpler on both counts—it can be taken with or without food and has fewer significant interactions.
Who can't take each
| Avoid amoxicillin if | Avoid doxycycline if | |
|---|---|---|
| Allergy | Allergic to any penicillin | Allergic to any tetracycline |
| Pregnancy | Usually acceptable on advice | Not to be used |
| Breastfeeding | Usually acceptable on advice | Generally avoided |
| Children | Suitable, weight-based dosing | Not under 12 |
| Other | Caution with glandular fever—rash is common | Caution with liver problems; take care with sun exposure |
Doxycycline's restrictions in pregnancy and childhood exist for the same reason: tetracyclines bind to developing teeth and bone.
Is one more effective?
The evidence doesn't support a clear winner. Trials comparing antibiotics for acute bacterial sinusitis find broadly similar cure rates, which is why guidelines choose on stewardship, safety and practicality rather than on potency.
There's a more important point behind this comparison. Most sinusitis doesn't need an antibiotic at all—it's viral, and it settles. Choosing between two antibiotics is only relevant once you've reached the threshold where one is genuinely indicated. Our guide on whether you need antibiotics for a sinus infection covers that threshold, and steroid spray vs antibiotics covers the situations where a spray is the better answer.
How the choice is actually made
1
Is an antibiotic needed at all?
Ten days without improvement, or clear worsening after initial improvement, with features suggesting bacterial infection. If not, no antibiotic—and no comparison to make.
2
Can you take penicillin?
If yes, phenoxymethylpenicillin is the UK first-line choice. If you have a genuine penicillin allergy, that rules out the whole penicillin class including amoxicillin.
3
Is doxycycline suitable for you?
Not in pregnancy, not while breastfeeding, not under 12, and with caution where sun exposure is unavoidable or you take warfarin.
4
What can you realistically take?
Dosing frequency, interactions with your existing medicines, and previous experience of side effects all feed into the final decision.
Worth being precise about penicillin allergy. Many people carry a penicillin allergy label from childhood that turns out on assessment to describe a viral rash rather than a true allergy. Being incorrectly labelled means being given broader alternatives for the rest of your life. If you're unsure, ask your GP about formal allergy assessment.
Get Sinusitis Treatment Assessed
For adults 18 and over. A GPhC-registered pharmacist independent prescriber reviews your consultation and decides whether an antibiotic, a steroid nasal spray or neither is appropriate for your symptoms.
Start Sinusitis Consultation →If it's not working
No improvement after three days of either antibiotic usually means one of the following, and none of them is solved by switching to the other one:
- The infection was never bacterial. The most common explanation, and the reason a second antibiotic won't help either.
- Doses are being missed, or doxycycline is being taken alongside indigestion remedies or iron.
- Blockage rather than infection is now the problem, in which case a steroid nasal spray is what's needed.
- The diagnosis is something else—migraine, dental pain or allergic rhinitis can all mimic sinusitis.
- A complication has developed, which is uncommon but needs urgent assessment.
Seek urgent assessment for swelling or redness around an eye, a bulging eye, vision changes, a severe headache unlike your usual ones, neck stiffness, or confusion. Don't wait to see whether the antibiotic starts working.
Frequently Asked Questions
Which is better for sinusitis, amoxicillin or doxycycline?
Neither is better in general terms. Trials comparing antibiotics for acute bacterial sinusitis find broadly similar cure rates, so the choice is made on the individual rather than on effectiveness. Penicillin allergy, pregnancy, age, other medicines and how many doses a day you can realistically manage all matter more than any difference in potency. In UK practice, a penicillin is first-line and doxycycline is the main alternative.
Why does UK guidance not recommend amoxicillin first for sinusitis?
This surprises people who have read American advice, where amoxicillin or amoxicillin with clavulanic acid is standard. NICE NG79 recommends phenoxymethylpenicillin as the first-line choice for acute sinusitis in the UK. It is a narrower-spectrum penicillin, which means it targets the likely bacteria while doing less collateral damage to other bacteria in the body, and that fits UK antimicrobial stewardship policy.
Can I take doxycycline if I am allergic to penicillin?
Yes. Doxycycline is a tetracycline and is chemically unrelated to penicillins, so there is no cross-reactivity. This is the main reason it is used for sinusitis in the UK. It is the standard alternative for adults with a genuine penicillin allergy, provided there is no other reason to avoid it such as pregnancy.
Which has fewer side effects?
They differ rather than one being clearly gentler. Penicillins more often cause diarrhoea, nausea and thrush. Doxycycline more often causes nausea, sensitivity to sunlight, and irritation of the gullet if taken lying down or without enough water. Doxycycline also has more interactions, because indigestion remedies, iron and calcium bind to it and stop it being absorbed properly.
How many times a day do you take each one?
Doxycycline for sinusitis is usually taken once daily after a loading dose on the first day. Phenoxymethylpenicillin is taken four times a day, spaced through the waking day and on an empty stomach. That practical difference matters more than people expect, because missed doses are the most common reason a course fails, and a four-times-daily schedule is harder to keep to.
Can I take doxycycline in pregnancy?
No. Doxycycline should not be used in pregnancy or while breastfeeding, because tetracyclines can affect developing teeth and bone. It is also not used in children under 12 for the same reason. If you are pregnant, breastfeeding or trying to conceive, tell the prescriber, and expect to be directed to your GP or midwife rather than treated online.
Does either work faster?
No meaningful difference. With either antibiotic, most people notice some improvement within two to three days if a bacterial infection was genuinely the problem. Both courses should be completed as prescribed even once you feel better. If there is no improvement at all after three days, contact a clinician rather than assuming the other antibiotic would have worked.
Can I switch from one to the other if it is not working?
Not on your own. If a course is not working, the most common explanation is that the infection was never bacterial, in which case a different antibiotic will not help either. Other possibilities include a complication or a different diagnosis altogether. Contact a clinician rather than starting a second course. Do not use leftover antibiotics from a previous illness.
Completing the treatment
Access Doctor supplies phenoxymethylpenicillin for sinusitis as the UK first-line antibiotic, and doxycycline capsules for sinusitis for adults who can't take penicillin. Where the problem is persistent inflammation rather than bacterial infection, mometasone nasal spray or beclometasone nasal spray may be more appropriate. All are prescription-only and follow an online consultation reviewed by a pharmacist independent prescriber, who may decline where an antibiotic isn't indicated.
Antibiotic · Rx
Phenoxymethylpenicillin for Sinusitis
UK first-line antibiotic for bacterial sinusitis.
View product →Antibiotic · Rx
Doxycycline Capsules for Sinusitis
Once-daily alternative for penicillin allergy.
View product →Steroid spray · Rx
Mometasone Nasal Spray for Sinusitis
For persistent inflammation rather than infection.
View product →Steroid spray · Rx
Beclometasone Nasal Spray for Sinusitis
Alternative steroid nasal spray, taken twice daily.
View product →References
- National Institute for Health and Care Excellence. Sinusitis (acute): antimicrobial prescribing (NG79). nice.org.uk
- NICE Clinical Knowledge Summaries. Sinusitis. cks.nice.org.uk
- Joint Formulary Committee. British National Formulary: Doxycycline. bnf.nice.org.uk
- Joint Formulary Committee. British National Formulary: Amoxicillin. bnf.nice.org.uk
- Joint Formulary Committee. British National Formulary: Phenoxymethylpenicillin. bnf.nice.org.uk
- NHS. Sinusitis (sinus infection). nhs.uk
- UK Health Security Agency. Managing common infections: guidance for primary care. gov.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Antibiotic choice is a clinical decision made by a prescriber who has assessed you. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.