Quick reality check: cefaclor’s peak fame was the 90s, but in 2025 it’s still on Aussie scripts-just not as the first pick for many common infections. If you’ve been handed a bottle or you’re googling it for your kid’s ear infection, you want straight answers: what it treats, how to take it right, and when there’s a better option. That’s what you’ll get here-no fluff, just safe, evidence-based guidance you can act on today.

• TL;DR: A second‑generation cephalosporin antibiotic used for ear, sinus, throat, skin, and some urinary infections-often as an alternative when first‑line drugs aren’t suitable.
• Typical adult dose: 250-500 mg every 8 hours; kids: 20-40 mg/kg/day split into 3 doses (don’t exceed 1 g/day). Take with food.
• Common side effects: diarrhoea, nausea, rash. Red flags: hives/swelling, severe diarrhoea, joint pains with rash/fever (serum sickness‑like reaction-see a doctor).
• Not ideal as first choice for many infections in Australia; amoxicillin/cephalexin often beat it for common cases. Check your specific diagnosis.
• Warfarin users: monitoring may be needed (INR can rise). Probenecid can raise levels. Avoid live typhoid vaccine during treatment.

What you probably need right now:

• Is cefaclor the right antibiotic for this infection?
• Exact dosing and timing for adults and kids, including missed-dose rules.
• Side effects to expect vs signs you need urgent care.
• How it compares to amoxicillin and cephalexin in 2025 Australia.
• What to do if you’ve got penicillin allergy, kidney issues, pregnancy, or breastfeeding.

What cefaclor does, who it’s for, and when it’s not the right antibiotic

Cefaclor is an oral second‑generation cephalosporin. It targets many Gram‑positive bacteria (like Streptococcus pyogenes) and some Gram‑negatives (like Haemophilus influenzae and Moraxella catarrhalis). In clinics here in Australia, it shows up for ear infections, sinusitis, strep throat, skin infections, and some urinary tract infections. It’s not the go‑to for all of these, but it can be a smart alternative when first‑line choices won’t work-say due to intolerance, local resistance patterns, or specific bug coverage.

How it fits into 2025 practice in Australia:

• Ear infections (otitis media): can be used, especially if amoxicillin isn’t suitable; some clinicians prefer amoxicillin-clavulanate or cefuroxime for beta‑lactamase producers.
• Sinusitis: reserved for bacterial cases with persistent/worsening symptoms; amoxicillin (or amoxicillin-clavulanate) is often first line.
• Strep throat: penicillin or amoxicillin is first choice. Cefaclor is an option if those aren’t tolerated.
• Skin infections: cephalexin usually wins; cefaclor is an alternative if broader coverage for some Gram‑negatives is wanted.
• UTIs: nitrofurantoin or trimethoprim are typical first‑line for uncomplicated cystitis; cefaclor is considered when those aren’t appropriate.

What it doesn’t cover well:

• MRSA and many hospital bugs-don’t expect it to touch those.
• Atypicals like Mycoplasma-macrolides or doxycycline are used there.
• Beta‑lactamase producers can reduce its effectiveness-your doctor considers this when choosing.

Australian context (Hobart included): prescribing follows Therapeutic Guidelines (Antibiotic), local resistance data, and PBS listings. Cefaclor products here include capsules (250 mg, 500 mg), modified‑release tablets (often 375 mg, branded “CD”), and oral suspensions (125/250 mg per 5 mL). Most suspensions need refrigeration after mixing and expire within 14 days-more on that below.

Therapeutic Guidelines: Antibiotic (Australia, 2024 update) puts stewardship first: “Use antibiotics only when bacterial infection is likely, choose the narrowest effective agent, and treat for the shortest effective duration.”

Who might avoid cefaclor:

• History of immediate anaphylaxis to penicillin or cephalosporins-cross‑reactivity is uncommon but real; avoid and discuss alternatives.
• Previous serum sickness‑like reaction (SSLR) to cefaclor-don’t rechallenge.
• Severe kidney impairment-dose interval adjustments are usually needed.

Pregnancy and breastfeeding (Australia, 2025): cephalosporins are generally considered safe in pregnancy; small amounts pass into breast milk and can cause loose stools or thrush in some infants. If you’re pregnant or breastfeeding, confirm with your clinician for your exact scenario (infection, trimester, other meds).

Note: Doses are typical ranges from Australian references; your prescriber fine‑tunes per bug, severity, and kidney function.

How to use cefaclor safely: dosing, timing, interactions, side effects

Getting the small stuff right is how you get better faster and dodge trouble. Here’s the practical, no‑nonsense way to take it.

Step‑by‑step for adults:

1. Confirm the dose and schedule on your label. Standard: 250-500 mg every 8 hours; modified‑release (CD): often 375 mg every 12 hours.
2. Take with food or milk to reduce nausea. Set phone alarms for 8‑hour spacing (e.g., 7am, 3pm, 11pm).
3. Missed a dose? Take it if you remember within ~4 hours. If it’s close to the next dose, skip and resume. Don’t double up.
4. Finish the prescribed course unless your clinician advises otherwise. Don’t save leftovers.
5. Watch for red‑flag reactions (below). If they show up, stop and seek medical advice.

For kids (suspension):

• Dose is weight‑based. Common ranges: 20-40 mg/kg/day divided into 3 doses; do not exceed 1 g/day. Your script label should show mL per dose.
• Shake the bottle well before each use. Most cefaclor suspensions are kept in the fridge and discarded after 14 days-check the label.
• Use an oral syringe, not a kitchen spoon. If they spit it out immediately, you can usually redose; if it’s been a few minutes, do not redose-ask your pharmacist.

Kidney issues: with significantly reduced kidney function (e.g., CrCl < 30 mL/min), your prescriber may extend the interval (e.g., every 12 hours). If you’re on dialysis, timing often shifts to post‑dialysis dosing-get specific instructions.

Interactions that matter:

• Warfarin: antibiotics can reduce gut vitamin K and raise INR. If you’re on warfarin, let your prescriber know; extra INR checks may be needed.
• Probenecid: increases cefaclor levels; not usually combined unless intended.
• Live oral typhoid vaccine: effectiveness can drop if taken close together-space them well apart.
• Lab tests: cephalosporins can cause false‑positive urine glucose with copper‑reduction tests and a positive direct Coombs’ test.

Common side effects (usually mild):

• Diarrhoea or soft stools (most common), nausea, abdominal discomfort.
• Mild skin rash without other symptoms-still report it, especially if it worsens.
• Headache, dizziness (less common).

Serious or urgent signs-seek care fast:

• Hives, swelling of lips/tongue/face, wheeze, trouble breathing (possible immediate allergy).
• Severe or bloody diarrhoea, stomach cramps, fever (possible C. difficile infection).
• Widespread itchy rash with fever and joint pains around day 7-10, especially in children-this can be a known cefaclor‑linked serum sickness‑like reaction. Stop the drug and get assessed.
• Blistering rash or peeling skin (rare but serious).

Penicillin allergy questions:

• If you had a mild, delayed rash to penicillin years ago, many clinicians will still consider cephalosporins with caution.
• If you had immediate anaphylaxis to penicillin (hives in minutes, breathing issues), avoid cephalosporins like cefaclor unless an allergy specialist advises otherwise.

Alcohol? Moderate drinking isn’t known to cause a disulfiram‑type reaction with cefaclor, but alcohol can worsen dehydration if you already have diarrhoea. If you’re sick, hydrate and keep it easy.

Practical tips that reduce risk:

• Take doses evenly spaced; missed‑dose mistakes are a common reason antibiotics seem to “not work.”
• Swallow capsules whole with a full glass of water; MR tablets should not be crushed or chewed.
• Store suspension in the fridge (if the label says so) and mark the discard date on the bottle.
• If you’re not improving by 48-72 hours or you’re getting worse, reach out to your clinic-your bug may be resistant or the diagnosis may need a rethink.

Decisions, scenarios, and next steps: amoxicillin vs cefaclor, FAQs, troubleshooting

Choosing between common antibiotics isn’t about brand loyalty-it’s about the bug, the body site, allergies, and local resistance. Here’s how clinicians often frame it in Australia in 2025.

Cefaclor vs amoxicillin (big picture):

• For strep throat and many ear/sinus infections, amoxicillin remains first line: narrower spectrum, excellent activity against Streptococcus, and a long safety record.
• Cefaclor steps in when amoxicillin isn’t a fit (intolerance, prior failure, or need for a different spectrum). It has activity against some organisms that resist amoxicillin, but not universally.
• For skin infections, cephalexin often wins; cefaclor is considered if Gram‑negative coverage is desired.
• For uncomplicated UTIs, nitrofurantoin or trimethoprim usually beat both amoxicillin and cefaclor unless culture says otherwise.

Trade‑offs that matter to you:

• Side effect profile: cefaclor has a specific association with serum sickness‑like reactions in children (still uncommon but more than with many peers). If your child developed rash + joint pains after cefaclor before, avoid rechallenge.
• Dosing convenience: cefaclor often requires three times daily dosing; modified‑release helps but isn’t appropriate for every infection.
• Cost/access: in Australia, cefaclor is generally PBS‑listed; your out‑of‑pocket depends on concession status.

Handy decision heuristics (not a substitute for your doctor’s advice):

• If the infection is likely strep throat and you’re not allergic: penicillin or amoxicillin is simplest and effective.
• If your child has recurrent ear infections with suspected beta‑lactamase producers, clinicians may consider amoxicillin-clavulanate or cefuroxime; cefaclor is an alternative in some cases.
• If you’ve had immediate anaphylaxis to penicillin: avoid cefaclor; ask about macrolides, clindamycin, or other non‑beta‑lactams depending on the infection.

Mini‑FAQ:

• How fast will I feel better? Many people improve within 48 hours. If not, or if you worsen, check in with your clinician.
• Can I crush cefaclor? Don’t crush modified‑release tablets. Standard capsules shouldn’t be opened unless a pharmacist says it’s okay (they taste bitter).
• Is cefaclor a penicillin? No-it’s a cephalosporin. Some people allergic to penicillin can still take it, but severe penicillin allergy is a red flag.
• Can I take it with probiotics? If you want to try probiotics, separate by a few hours. Evidence is mixed; some people find they reduce diarrhoea.
• What if the suspension was left out overnight? If it should be refrigerated and sat out, ask your pharmacist whether to replace it-stability depends on time/temperature.
• Do I need food with it? It’s gentler with food and absorption is fine, so yes, pair it with meals.

Troubleshooting by scenario:

• Diarrhoea becomes severe or bloody: stop the antibiotic and seek medical care-risk of C. difficile is small but serious.
• Rash after day 7 with fever and sore joints (child or adult): think serum sickness‑like reaction. Stop and get seen promptly.
• Warfarin user notices nosebleeds or bruising: arrange an INR check; your dose may need tweaking during/after therapy.
• Missed multiple doses: don’t double to catch up. Restart the regular schedule and let your prescriber know if symptoms lag.
• No improvement at 72 hours: call your clinic. You may need culture tests, a different antibiotic, or a non‑antibiotic diagnosis (e.g., viral).

Safety note and why stewardship matters:

Antibiotic resistance is local and moving. In Tasmania and across Australia, prescribers lean on culture results and evolving guidelines. That’s why what worked for your neighbour isn’t necessarily right for you. Shortest effective duration and the narrowest effective drug aren’t buzzwords-they reduce side effects for you now and keep antibiotics working later.

Where this guidance comes from: Australian Therapeutic Guidelines: Antibiotic (2024 update), Australian Medicines Handbook (2025), NPS MedicineWise, and global resources like the CDC’s antibiotic safety notes. Those sources line up on the big points above: when to use cefaclor, how to dose, watch‑outs, and when to consider alternatives.

Next steps:

• If you already have a cefaclor script, read your label, set alarms, and take the first dose with food.
• If you’re not sure it’s the right drug, call your prescriber before starting-especially if you have a history of severe beta‑lactam allergy, are pregnant, or have kidney disease.
• Parents: record the time of each dose, store the suspension correctly, and note any rash/fever in a quick diary. It helps your doctor if a review is needed.
• On day 3, check in with yourself: better, same, worse? That one question often catches resistant bugs early.

You don’t need to memorise any of this. Save the page, follow your label, and use the checklists when you need them. If something feels off, reach out-early tweaks beat late regrets every time.