Amoxicillin, ciprofloxacin, doxycycline and metronidazole together cover many common bacterial infections, with cephalexin, azithromycin, co-trimoxazole and clindamycin as useful additions, but each has gaps and hazards and none treats viral illness. Penicillin allergy is the first hazard to check before any penicillin-class drug is used, because a severe reaction can kill and there may be no emergency care. Strengths and course lengths are not given here and must come from a reference.
Part of Critical Drugs to Prioritize
Antibiotics are the most valuable group in the raid and the easiest to misuse, since each drug covers some bacteria and none covers viruses.
Antibiotics Treat Bacteria, And Only Some Of Them
An antibiotic acts on bacteria. It does nothing for a cold, influenza or other viral illness, and a drug that does not fit the infection is a wasted supply and a risk. Different antibiotics cover different bacteria, which is why a small range is worth having, and why a drug that suits one infection may fail another.
Infection is a leading preventable cause of death when medical care is gone, and antibiotics cannot be made without a pharmaceutical laboratory. That is why they rank first in Critical Drugs to Prioritize. Basic infection control, covered in Infection Prevention, reduces how many you need.
The First Group
| Drug | Class | Generally used for | Main cautions |
|---|---|---|---|
| Amoxicillin | Penicillin | Ear, sinus, throat, dental, urinary and skin infections | Penicillin allergy; diarrhoea |
| Ciprofloxacin | Fluoroquinolone | Urinary and gut infections, some respiratory and wound infections | Generally avoided in children and pregnancy; tendon problems |
| Doxycycline | Tetracycline | Tick-borne illness, respiratory and skin infections, some sexually transmitted infections | Stains developing teeth, so avoided in pregnancy and young children; sun sensitivity |
| Metronidazole | Nitroimidazole | Anaerobic (oxygen-free) infections such as dental and abdominal abscess; giardia | Severe reaction with alcohol |
Useful Additions
| Drug | Class | Generally used for | Main cautions |
|---|---|---|---|
| Cephalexin | Cephalosporin | Skin and soft-tissue infections, strep throat | Some people allergic to penicillin also react |
| Azithromycin | Macrolide | Respiratory infections, some sexually transmitted infections, travellers’ diarrhoea | Can affect heart rhythm in some people |
| Co-trimoxazole (Bactrim) | Sulfonamide combination | Urinary and some skin infections | Sulfa allergy; rare severe skin reactions |
| Clindamycin | Lincosamide | Dental and skin infections, bone infection | Can cause severe diarrhoea from C. difficile |
The tables describe general use. They are not prescriptions, they give no strength or course length, and an infection that does not improve needs more than a drug from this list.
Method: Before Using Any Antibiotic
Step 1: Ask whether the illness is bacterial. A cold, most sore throats and influenza are viral. Antibiotics will not help them.
Step 2: Ask about allergy. Has the person ever reacted to penicillin, cephalosporins or sulfa drugs? If the answer is unknown, the risk is real.
Step 3: Identify the drug. Check the label, name, strength and expiry. See Medications That Genuinely Expire for tetracycline and liquid forms.
Step 4: Take the amount and length from a reference. Not from memory, and not from a previous patient’s label.
Step 5: Watch for improvement and for reactions. Rash, swelling of the face or throat, or difficulty breathing is an emergency.
Common Mistakes
- Using a leftover course for a new illness. It was chosen for a different person and infection.
- Treating viral illness. It wastes supply.
- Taking a partial course and stopping. The right course length is a reference matter; this article does not specify it.
Safety
A severe allergic reaction to an antibiotic can become fatal quickly
Swelling of the lips, face or throat, wheezing or collapse after a dose is anaphylaxis. Stop the drug and see Critical Specialty Medications for epinephrine and Medical Emergencies for the response. Do not guess amounts; take them from a reference.
What’s Next
- Learn next: Pain & Fever Management — the next group
- Combine with: Infection Prevention — fewer infections, fewer antibiotics