Antibiotic comparison: know which drug fits the infection

Not all antibiotics treat the same bugs. Picking the right one matters for your recovery and for preventing resistance. Below I break down common antibiotic classes, what they’re usually used for, and the most important safety flags to watch for.

Common antibiotic classes and when they’re used

Here are the names you’ll see most often and a quick note on where each one fits:

Penicillins (amoxicillin, penicillin V) — First-line for many ear, throat, and skin infections. Safe for most people unless you have a true penicillin allergy. Good for strep throat and some respiratory infections.

Cephalosporins (cephalexin, cefuroxime) — Often used for skin infections, UTIs, and respiratory problems when penicillin can’t be used. Cross-reactivity with penicillin allergy is possible but uncommon; tell your doctor about severe reactions.

Macrolides (azithromycin, clarithromycin) — Handy for atypical pneumonia and some sinus infections. Watch interactions: macrolides can affect some heart and cholesterol meds.

Tetracyclines (doxycycline — Vibramycin) — Good for acne, some tick-borne illnesses, and respiratory infections. Avoid in pregnancy and children under 8. Increases sun sensitivity.

Fluoroquinolones (ciprofloxacin, levofloxacin) — Strong options for complicated UTIs and certain resistant infections. Use only when needed: they carry higher risks like tendon injury and nerve effects.

Metronidazole — Best for anaerobic infections and some abdominal or dental infections. Don’t drink alcohol while taking it.

How to choose safely — quick checklist

Ask these questions before starting an antibiotic:

- Is the infection bacterial? Antibiotics don’t help viral illnesses like colds or most sore throats.

- Which site is infected? Different drugs concentrate better in the lungs, urine, skin, or gut.

- Do you have allergies, are you pregnant, or do you take interacting meds? These change the safe options.

- Has a culture been taken in recurrent or severe cases? Culture and sensitivity testing pinpoints the best antibiotic and reduces guessing.

- Can a narrow-spectrum drug work? Narrow choices target the bug and reduce resistance compared with broad-spectrum drugs.

Practical tips: always finish the prescribed course unless your doctor says stop; don’t use leftover antibiotics; keep a list of past reactions; and if symptoms worsen or don’t improve in 48–72 hours, contact your provider. For specific swaps — like alternatives to Vibramycin — check our article comparing options and pros/cons so you can discuss safe alternatives with your clinician.

If you want, tell me the type of infection and any allergies or pregnancy status and I’ll help you compare likely antibiotic choices and the main safety points to raise with your prescriber.