Amoxicillin
- Class: Penicillin
- Used for: a bacterial infection
- Say it: uh-mox-ih-SIL-in
- Forms: capsule, tablet, chewable tablet, oral liquid
AMOXICILLIN is KILLIN' the bacteria — it bursts the wall and the cell blows apart.
Every -CILLIN blocks cell-wall cross-linking, so the growing bacterium ruptures under its own pressure. Bactericidal, not merely inhibitory.
Beta-lactams block the enzymes that cross-link the bacterial wall. Only a growing bacterium is building wall, which is why these drugs kill dividing organisms best.
Side effects
Common: diarrhea, nausea, rash
Serious: anaphylaxis, C. difficile infection
Typical dose
500 mg three times daily
875 mg twice daily or 1 g three times daily for more severe infection.
Check yourself
A patient with glandular fever develops a widespread rash after amoxicillin. What does it mean?
- A characteristic non-allergic rash seen with EBV — not a true penicillin allergy
- Anaphylaxis is beginning
- The infection is resistant to amoxicillin
- A lifelong penicillin allergy has been demonstrated
Show answer
A. A characteristic non-allergic rash seen with EBV — not a true penicillin allergy
The rash is maculopapular and itchy but has none of the features of anaphylaxis — no wheeze, no swelling, no collapse. Mislabelling it as allergy is one of the commonest avoidable errors in prescribing.
See it, don't memorize it
The app has the mechanism comic and a patient case for Amoxicillin – plus the name link, the class mnemonic, pronunciation you can hear, and a self-check, for the top 100 drugs. One purchase, no subscription, no account.