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Condition guide · /antibiotics/
Antibiotics for bacterial infections
Reviewed by Dr. Arjun Mehta, PharmD — Head Pharmacist. Updated May 2025.
4
3–7 days
Typical course
80%
Of prescriptions in primary care
Critical
Resistance is global
About this condition
Antibiotics treat bacterial infections — they do not work against viruses, including the common cold, most sore throats and influenza. Using them when they are not needed drives antibiotic resistance, which is now considered one of the top global health threats.
The right antibiotic depends on the infection, the likely organism, local resistance patterns and patient allergies. Penicillins (amoxicillin, co-amoxiclav) cover most chest and ear infections. Macrolides (azithromycin) are alternatives for penicillin-allergic patients. Fluoroquinolones and tetracyclines have specific indications. Complete the full course your prescriber recommends, even if you feel better quickly.
Treatment options
Amoxicillin / co-amoxiclav
Penicillins — first-line for many respiratory, ear and dental infections. Inexpensive and well-studied.
Azithromycin
Macrolide — useful for chest infections in penicillin-allergic patients and for some sexually transmitted infections.
Doxycycline
Tetracycline — used in acne, atypical pneumonia, malaria prevention and certain tick-borne diseases.
Nitrofurantoin
Specific to urinary infections. Concentrates in urine, broad coverage of common urinary pathogens.
Common questions
Why must I finish the full course?
An incomplete course leaves the more resistant bacteria alive, increasing the chance of relapse and resistance.
Can I take antibiotics for a cold?
No. Colds are viral. Antibiotics will not help and will expose you to side effects and resistance risk.
Will antibiotics affect my contraception?
Most antibiotics do not affect combined hormonal contraception. Older advice about back-up methods has largely been retired — but rifampicin and rifabutin remain exceptions.
Dr. Arjun Mehta, PharmD · Head Pharmacist
/our-pharmacists/arjun-mehta/ — Reviewed May 2025
This guide is reviewed every 12 months or sooner when clinical guidance changes. If you have a specific medical question, call our pharmacist team — we answer the phone, not a bot.
