Amoxicillin in Australia: Uses, Dosing, and What to Know

Amoxicillin is a penicillin-type antibiotic and the most frequently prescribed antibiotic in Australia. It is effective against a wide range of common bacterial infections and has been in clinical use since 1972. This guide covers what amoxicillin treats, how to take it, side effects, and the critical distinction between bacterial infections (where antibiotics help) and viral infections (where they do not).

What Amoxicillin Treats

Amoxicillin is effective against many gram-positive and some gram-negative bacteria. The Australian Therapeutic Guidelines (eTG) recommend it as first-line treatment for several common infections:

• Acute bacterial sinusitis (when criteria for antibiotic treatment are met)
• Acute otitis media (middle ear infection)
• Streptococcal pharyngitis/tonsillitis (confirmed or strongly suspected strep throat)
• Community-acquired pneumonia (mild, in combination or as first-line)
• Urinary tract infections (less commonly now due to resistance patterns)
• H. pylori eradication (as part of triple therapy with a PPI and clarithromycin)
• Dental infections
• Skin infections (some types)

What Amoxicillin Does NOT Treat

Australian data shows that antibiotics are still over-prescribed for conditions that are usually viral. If your doctor determines that your infection is likely viral, the appropriate treatment is rest, fluids, and symptomatic relief -- not antibiotics. A good doctor will explain why they are not prescribing antibiotics, not just hand over a script to end the consultation.

Dosing

• Mild infections: 500mg every 8 hours (three times daily)
• Moderate infections: 500mg-1g every 8 hours
• Duration: typically 5-7 days for most infections; 10 days for strep throat; 14 days for H. pylori
• Take with or without food -- amoxicillin is well absorbed either way
• Space doses as evenly as possible (e.g., 7am, 3pm, 11pm for three times daily)

Side Effects

Common (5-10%)

• Diarrhoea (most common -- amoxicillin disrupts gut flora)
• Nausea
• Skin rash (non-allergic amoxicillin rash occurs in ~5-10%, especially with concurrent viral infections like glandular fever)

Uncommon but important

• Vaginal thrush (candidiasis) -- antibiotics disrupt normal bacterial balance
• Allergic reactions: true penicillin allergy occurs in ~1-2% of the population. Symptoms include urticaria (hives), angioedema, and rarely anaphylaxis

Penicillin Allergy

Many people believe they are allergic to penicillin, but studies show that over 90% of people labelled "penicillin allergic" can actually tolerate penicillins safely. Common childhood rashes during antibiotic courses are often viral (coincidental) rather than true drug allergies. If you have a "penicillin allergy" label, discuss it with your doctor -- allergy testing may be appropriate to clarify, as the label can limit your antibiotic options unnecessarily.

Amoxicillin and the Contraceptive Pill

The interaction between standard antibiotics (including amoxicillin) and the oral contraceptive pill has been largely debunked. Current evidence and Australian guidelines indicate that non-enzyme-inducing antibiotics like amoxicillin do not reduce the effectiveness of the combined oral contraceptive pill. The exception is rifampicin and rifabutin, which are enzyme-inducing and do affect the pill.

Antibiotic Resistance

Antibiotic resistance is one of the most significant public health threats globally. Australia's Antimicrobial Resistance Strategy emphasises responsible prescribing. You can help by:

• Only taking antibiotics when prescribed by a doctor for a confirmed or strongly suspected bacterial infection
• Completing the full course as prescribed
• Never sharing antibiotics or using leftover antibiotics from a previous course
• Not pressuring your doctor for antibiotics when they advise against them
• Understanding that most colds, sore throats, and coughs are viral and do not need antibiotics

PBS Status and Cost

• PBS listed: Yes, for appropriate bacterial infections
• Cost: PBS co-payment (general or concession)
• Without PBS: approximately $8-$15 for a standard course
• Available as capsules, tablets, and oral suspension (liquid, for children or those who can't swallow tablets)

Getting Amoxicillin Prescribed

Amoxicillin is a Schedule 4 (prescription-only) medication. Antibiotics should only be prescribed after a clinical assessment determines that a bacterial infection is likely or confirmed. Telehealth can be appropriate for some antibiotic prescribing -- for example, when symptoms and history strongly suggest a specific bacterial infection (such as UTI in a woman with recurrent, well-characterised episodes). For conditions requiring examination (throat inspection, ear examination), in-person assessment is more appropriate.