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Antibiotics treat bacterial chest infections and exacerbations. This page lists the core oral and IV agents, their typical uses and the points a physiotherapist should know — including when clearance is best timed and which agents can cause bronchospasm. Inhaled antibiotics used long-term in chronic infection are covered under nebulised therapy.
Antibiotics treat the bacterial chest infections that drive many respiratory exacerbations.1 The choice depends on the likely organism, the severity and setting, any allergies, and local resistance patterns — guided in Australia by Therapeutic Guidelines: Antibiotic.2 For physiotherapy the key point is that antibiotics and airway clearance work together: clearing secretions helps the drug reach the airways, and starting a course is often the trigger to step up clearance during an exacerbation. Inhaled and nebulised antibiotics are also used for chronic infection in bronchiectasis and cystic fibrosis, and are always given after airway clearance. The table below summarises the agents commonly seen in cardiorespiratory practice.
Core antibiotics in respiratory disease
| Antibiotic | Route | Typical adult dose | Common respiratory indications | Implications for physiotherapy |
|---|---|---|---|---|
| Amoxicillin | Oral | 500 mg–1 g tds | Mild CAP, pneumococcal pneumonia, AECOPD, otitis, sinusitis | First-line for most community-acquired infection in non-penicillin-allergic patients |
| Amoxicillin-clavulanate | Oral | 875/125 mg bd | Moderate CAP, aspiration pneumonia, bronchiectasis exacerbation | Broader gram-negative and anaerobic cover. GI side effects common |
| Amoxicillin-clavulanate | IV | 1.2 g tds | Moderate-severe CAP, aspiration pneumonia, HAP (low risk), bronchiectasis exacerbation | IV-to-oral switch typically at 48–72 h |
| Doxycycline | Oral | 100 mg bd | CAP (atypical cover), AECOPD, Mycoplasma, Chlamydia | First-line option in penicillin-allergic CAP. Photosensitivity warning |
| Azithromycin | Oral | Acute: 500 mg day 1 then 250 mg daily ×4. Maintenance (bronchiectasis, CF): 250–500 mg three times weekly | Atypical CAP, pertussis, Legionella. Long-term low-dose for frequent exacerbators | Long half-life. QT prolongation risk. Before maintenance therapy is started, sputum must be cultured for NTM — macrolide monotherapy in undiagnosed NTM infection induces resistance and can remove the key drug from a future treatment regimen. Baseline QTc; hearing assessment in long-term use |
| Azithromycin | IV | 500 mg daily | Severe CAP, Legionella | IV reserved for severe disease |
| Clarithromycin | Oral | 500 mg bd | Atypical CAP, NTM combination therapy | More drug interactions than azithromycin (CYP3A4 inhibitor) |
| Roxithromycin | Oral | 300 mg daily or 150 mg bd | Atypical CAP, AECOPD | Australian macrolide alternative |
| Cefalexin | Oral | 500 mg qid | Step-down from IV cephalosporin | Limited respiratory role as monotherapy |
| Cefuroxime | Oral / IV | 500 mg bd PO; 750 mg–1.5 g tds IV | CAP, AECOPD | Limited atypical cover |
| Ceftriaxone | IV / IM | 1 g daily (2 g for severe CAP) | Moderate-severe CAP, hospitalised pneumonia, empirical sepsis | Once-daily dosing. Pair with macrolide for atypical cover |
| Cefepime | IV | 1–2 g bd–tds | HAP/VAP, febrile neutropenia, Pseudomonas cover | Anti-pseudomonal fourth-generation cephalosporin |
| Piperacillin-tazobactam | IV | 4.5 g qid (or extended-infusion) | HAP, aspiration with severe sepsis, neutropenic fever, CF exacerbation with Pseudomonas | Broad gram-negative including Pseudomonas + anaerobes |
| Meropenem | IV | 1 g tds (2 g tds for severe) | Severe HAP/VAP, MDR gram-negatives, CF/bronchiectasis with resistant Pseudomonas | Reserved per stewardship |
| Ceftazidime | IV | 1–2 g tds | Pseudomonas in CF, bronchiectasis, HAP | Anti-pseudomonal cephalosporin |
| Ciprofloxacin | Oral / IV | 500–750 mg bd PO; 400 mg bd–tds IV | Pseudomonas in bronchiectasis/CF exacerbation, Legionella | Tendinopathy risk (especially Achilles, in older patients on concurrent steroids — relevant to exercise programmes), QT prolongation |
| Moxifloxacin | Oral / IV | 400 mg daily | Severe CAP, penicillin-allergic CAP | QT prolongation, hepatotoxicity, photosensitivity |
| Vancomycin | IV | 25–30 mg/kg loading then 15–20 mg/kg bd | MRSA pneumonia, post-influenza S. aureus, severe HAP | Trough or AUC monitoring required. Nephrotoxicity |
| Linezolid | Oral / IV | 600 mg bd | MRSA or VRE pneumonia | Excellent oral bioavailability. Thrombocytopenia with use >2 weeks |
| Trimethoprim-sulfamethoxazole | Oral / IV | 160/800 mg bd (PJP treatment up to 5 mg/kg of trimethoprim qid) | PJP treatment and prophylaxis, Stenotrophomonas, Nocardia | Hyperkalaemia, AKI. Drug interactions (warfarin, methotrexate) |
| Metronidazole | Oral / IV | 400 mg tds PO; 500 mg tds IV | Anaerobic cover in aspiration pneumonia, lung abscess | Avoid alcohol — disulfiram-like reaction |
| Tobramycin / gentamicin | IV / inhaled | IV: weight-based once daily; inhaled tobramycin 300 mg bd (cycle on/off) | IV: empirical gram-negative sepsis. Inhaled: chronic Pseudomonas suppression in CF | IV: nephrotoxicity, ototoxicity. Inhaled: bronchospasm, voice change |
| Colistin / colistimethate | Inhaled / IV | Inhaled 1–2 MIU bd; IV per protocol | Pseudomonas eradication in CF/bronchiectasis; MDR gram-negatives IV | Inhaled: bronchospasm — pre-treat with bronchodilator. IV: nephrotoxicity |
| Aztreonam | Inhaled / IV | Inhaled 75 mg tds (cycle on/off); IV 1–2 g tds | Inhaled: chronic Pseudomonas suppression in CF. IV: gram-negative in severe penicillin allergy | Inhaled: cough, wheeze on initiation |
| Rifampicin (combination) | Oral / IV | 450–600 mg daily | TB combination, NTM combination, persistent MRSA | Potent CYP inducer — major drug interactions. Orange discolouration of secretions, urine, contact lenses |
| Anti-tuberculous (HRZE) combination | Oral | Weight-based per Australian TB guidelines | Active tuberculosis: 2 months HRZE then 4 months HR | Managed through Queensland Health TB services. Multiple toxicities |
Physiotherapy timing around IV antibiotics: airway clearance is generally most effective when scheduled 30–60 minutes before a nebulised antibiotic (so the drug is deposited in cleared airways) and not immediately after IV antibiotic infusion if the patient is symptomatic.3
References & evidence base
- Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management and prevention of COPD: 2026 report. GOLD; 2026. Available at: goldcopd.org
- Therapeutic guidelines: antibiotic. Melbourne: Therapeutic Guidelines Limited; updated June 2026. Available at: tg.org.au
- Australian Medicines Handbook. Adelaide: Australian Medicines Handbook Pty Ltd, 2026.
References are numbered in citation order (Vancouver/BMJ style) and were current at the time of writing. Guidelines are living documents — verify against the latest version before clinical use. For drug-specific detail, including full product information, consult MedsInfo.
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