Home Drugs Amoxicillin


Amoxicillin is an antibiotic that doctors typically use to treat bacterial infections, especially those of the nose, ears, throat, lung, skin and urinary tract. They also prescribe it in combination with other medications for stomach ulcers H. pylori bacteria can cause.

Last Modified: April 25, 2024
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What Is Amoxicillin?

Amoxicillin is in the penicillin family of antibiotics, made from penicillium mold. It’s often prescribed as a generic drug, but is also available under brand names Amoxil, Larotid and Moxatag in the U.S.

This antibiotic belongs to a specific class of drugs called beta-lactams. Beta-lactam antibiotics such as amoxicillin work by binding proteins and inhibiting certain processes in bacterial cells. This causes the cell walls to break down and destroys the bacteria, a process called bactericidal killing.

What Is Amoxicillin Used to Treat?

Amoxicillin is used to treat a variety of bacterial conditions. Its effectiveness against multiple strains of bacteria explains why physicians consider it a strong antibiotic. Among the bacteria it fights are E. coli, salmonella, streptococcus species, Listeria monocytogenes and Clostridial species.

The Food and Drug Administration has approved amoxicillin to treat a variety of infections of the ear, nose, throat, genitourinary tract, skin, skin structure and lower respiratory tract.

Amoxicillin is FDA approved to treat:
  • Bacterial pharyngitis
  • Bronchitis
  • Tonsillitis
  • Pneumonia
  • Bacterial rhinosinusitis

Doctors sometimes prescribe amoxicillin for non-FDA-approved (off-label) uses. Examples are treatments for Lyme disease, infection prevention during certain surgeries (dental, hip, knee) and prevention of infectious endocarditis.

If you have questions about amoxicillin and off-label uses, speak with your doctor.

How to Take Amoxicillin

Doctors usually prescribe amoxicillin as an oral antibiotic, available in capsule, tablet and chewable tablet forms or as a suspension powder you can stir into a cold drink. You can take the drug before or after a meal, but it’s generally recommended that people with sensitive stomachs take it after eating.

In clinical or hospital settings, medical providers may give amoxicillin through an IV.

Amoxicillin dosages include:
  • 125 mg and 250 mg chewable tablets
  • 250 mg and 500 mg capsules
  • 500 mg and 875 mg tablets
  • 125 mg/5 mL and 250 mg/5mL oral suspension powder

Follow your doctor’s instructions about how to take amoxicillin, especially about daily dosages. Aim to take the medication at the same time every day as possible.

Recommended Dosages for Adults and Children

The right amoxicillin prescription or dosage depends on the specific infection and on the age and weight of the individual who needs it. Weight is a particularly important factor for children.

For maximum treatment benefits of amoxicillin, finish the full recommended doses your doctor prescribed. Even if you feel better midway through your prescription duration, it’s important to continue taking the drug.

Findings from one 2022 clinical research trial suggested that a short course of Amoxicillin (5 days) was just as effective as a longer course (10 days) for uncomplicated commonly acquired pneumonia in children under 10 years old.

Doubling up on a dose or taking two doses too close together to compensate for a missed dose is not advised. It’s safer to skip a missed dose and wait to take your next one.

Dosages for Impaired Kidney Function

Patients with chronic kidney disease (CKD), for example, have an impaired immune response and increased risk of infection. Antibiotics are commonly prescribed, however, CKD patients also experience impaired renal function, making metabolizing and eliminating medications such as antibiotics more challenging. This can lead to antibiotic accumulation and toxicity.

Doctors may prescribe lower doses than adults are typically prescribed. Sometimes individual doses are kept the same, but the time between doses is spaced out further. The mixed method combines these approaches to determine the correct balance of doses and their timing. 

Children 3 months old or younger typically are not prescribed more than a daily split dose of 30 mg/kg every 12 hours because their kidneys are underdeveloped.

Dosage for H. Pylori Infection

Doctors prescribe amoxicillin with clarithromycin and lansoprazole (Prevacid) to treat H. pylori infection. With triple therapy for adults, they usually recommend 500 mg clarithromycin, 30 mg lansoprazole, and 1 g amoxicillin. The dosage is twice a day (every 12 hours) for 14 days.

Patients on dual therapy for H. pylori infection should take 30 mg lansoprazole and 1 g amoxicillin three times a day (every eight hours) for 14 days.

Amoxicillin Overdose

You’re unlikely to experience any adverse effects from a mild overdose of amoxicillin. However, some people have experienced kidney problems that cause organ failure after overdosing on the antibiotic.

If you or a family member have a suspected overdose of amoxicillin, call the poison control center at (800) 222-1222, or visit the PoisonHelp.org website for helpful information.

Side Effects of Amoxicillin

Amoxicillin’s most common side effects are related to stomach upset and intestinal distress. These symptoms rarely require treatment beyond probiotics and over the counter medications, you should speak with your doctor if any side effects persist.

Common side effects of amoxicillin include:
  • Diarrhea
  • Nausea and vomiting
  • Headache
  • Skin rash or hives
  • Stomach problems

Two of Amoxicillin’s serious side effects are hypersensitivity or allergic reactions and Clostridium difficile-associated diarrhea (CDAD). Anyone who experiences a severe side effect after taking amoxicillin should seek immediate medical treatment.

Serious side effects of amoxicillin are:
  • Breathing difficulty
  • Swallowing difficulty
  • Blisters
  • Peeling skin
  • Inflammation or swelling of body parts (tongue, throat, eyes, face)
  • Stomach cramps
  • Wheezing
  • Watery stool with or without fever
  • Blood-stained stool

Stop taking amoxicillin and call 911 if you experience serious adverse reactions. Be sure to speak with your doctor or pharmacist about any other medications you may be taking to avoid amoxicillin drug interactions and potentially serious complications.

Amoxicillin Interactions

Check Amoxicillin’s label for a comprehensive list of medications that interact with it. Amoxicillin can strengthen or weaken other prescription and over-the-counter drugs. It can also create specific side effects.

  • Probenecid: The concentration of amoxicillin in your blood may increase if you use it together with probenecid, a gout medication.
  • Allopurinol: Skin rashes are more prevalent for people who take the gout medication allopurinol with amoxicillin.
  • Oral anticoagulants (blood thinners): The blood-thinning effects of oral anticoagulants like warfarin can increase when mixed with amoxicillin. Doctors may adjust the dosage of the blood thinner after checking anticoagulation levels.
  • Oral birth control pills: Amoxicillin’s effects on gut flora can make a combined dose of oral estrogen/progesterone contraceptives less effective.
  • Antibacterials: The ability of penicillin to treat bacterial infections may weaken if combined with other antibiotics like sulfonamides, tetracyclines, macrolides or chloramphenicol.

Amoxicillin can also influence medical tests. Urine tests for blood sugar levels, including Clinitest, Fehling’s Solution and Benedict’s Solution may return false-positive results for people on amoxicillin medication. More accurate glucose tests for people with diabetes include Clinistix and TesTape and other procedures that check for enzymatic glucose oxidase reactions.

Before Taking Amoxicillin

Amoxicillin can have dangerous side effects when mixed with certain medications. Let your pharmacist or doctor know if you have any allergies to amoxicillin or penicillin and if you take other antibiotics or blood thinners. The same is true if you take herbal medicines, multivitamins or nutritional supplements.

Women who breastfeed or are pregnant should alert their doctors about their pregnancy before starting a round of amoxicillin. So should anyone with a history of kidney disease, phenylketonuria or mononucleosis.

Non-Penicillin Antibiotic Alternatives

People allergic to amoxicillin have alternative medications. Non-penicillin antibiotics include Bactrim (trimethoprim) for ear, urine, respiratory and intestinal infections, clarithromycin (Biaxin) for stomach infections and stomach ulcers and clindamycin (Cleocin) for infections of the lungs and other internal organs, plus skin and blood infections.

Certain cephalosporins, such as Suprax, Ceftin and Keflex, are also ideal alternatives to amoxicillin.

Please seek the advice of a medical professional before making health care decisions.