Amoxicillin

What is Amoxicillin?

Amoxicillin is one of the most commonly prescribed antibiotics in the United States and worldwide. It belongs to the penicillin family and is used to treat a wide range of bacterial infections. It is available as capsules, tablets, chewable tablets, and oral suspension (liquid), and is generally prescribed to be taken two or three times a day. It always requires a prescription in the US and is only effective against bacterial infections — it does nothing for viruses.

What is it used for?

• Ear infections (acute otitis media) — one of the most common uses, especially in children
• Strep throat (streptococcal pharyngitis)
• Community-acquired pneumonia (chest infection)
• Urinary tract infections (UTIs)
• Dental infections and dental abscesses
• Skin and soft tissue infections
• Sinusitis caused by bacteria
• Lyme disease (early-stage)
• Prevention of endocarditis (heart valve infection) before certain dental procedures

How does it work?

Amoxicillin kills bacteria by preventing them from building their cell wall. All bacteria need a sturdy cell wall to survive — without it, they literally fall apart. Amoxicillin binds to proteins in the bacterial cell wall and disrupts the construction process, causing the bacteria to lyse (break open) and die. It works best against actively growing bacteria, which is why completing the full prescribed course matters — you need to eliminate all the bacteria, not just reduce them enough to feel better.

How do people commonly take it?

• Taken by mouth — capsules, tablets, chewable tablets, or liquid suspension
• Typical adult dose: 250mg–500mg every 8 hours, or 875mg every 12 hours, depending on the infection severity
• Can be taken with or without food
• Space doses evenly throughout the day — roughly every 8 hours for three-times-daily dosing
• Complete the entire prescribed course — even if symptoms resolve before it is finished
• Liquid amoxicillin must be refrigerated and used within 14 days of preparation
• Children's doses are calculated by weight — always use the prescribed amount

Common side effects

Most people take Amoxicillin without any problems, but side effects can happen. The most common ones include:

• Diarrhea — very common with amoxicillin, usually mild and self-limiting
• Nausea and vomiting
• Stomach pain or cramping
• Skin rash — a non-allergic maculopapular rash is common, particularly in people who have a concurrent viral illness
• Thrush (yeast infection) — antibiotics can disrupt the natural balance of bacteria in the body

Important safety points

• Always tell your prescriber about any previous reaction to penicillin or any antibiotic — this is critically important
• A flat, non-itchy, maculopapular rash during a course of amoxicillin is often not a true allergy — particularly in people who also have a viral illness at the time
• A true penicillin allergy (hives, facial swelling, difficulty breathing) is a medical emergency — call 911
• Current evidence suggests amoxicillin does not reduce the effectiveness of combined oral contraceptives — but discuss with your prescriber if you have concerns
• Probiotics taken alongside antibiotics may reduce antibiotic-associated diarrhea — ask your pharmacist
• Never share your antibiotic prescription with anyone else, even if their symptoms seem identical

Common mistakes to avoid

• Stopping the course early when symptoms improve — bacteria may not all be eliminated yet, and partial courses promote antibiotic resistance
• Demanding amoxicillin for a cold, the flu, COVID-19, or a viral sore throat — antibiotics are completely ineffective against viruses
• Using leftover amoxicillin from a previous prescription — wrong type, wrong dose, wrong duration for any new infection
• Confusing a non-allergic drug rash with a true allergic reaction — they look and behave differently; ask your pharmacist or doctor
• Failing to refrigerate the liquid suspension or use it within the prescribed timeframe
• Skipping doses or taking them irregularly — consistent levels in the bloodstream are needed to clear the infection

When to get medical advice

• If you develop hives, facial swelling, or difficulty breathing after taking amoxicillin — call 911 immediately (this is anaphylaxis)
• If you develop severe, frequent, or bloody diarrhea during or after your course — this may indicate C. diff infection
• If your infection does not show signs of improvement within 2–3 days of starting the course
• If you develop a severe skin reaction with blistering, peeling, or pain
• If your symptoms get significantly worse while taking amoxicillin