Amoxicillin: What It Is, Uses, Dosage, and Side Effects

Updated at 2025-05-10

Amoxicillin is a penicillin-class antibiotic that works by inhibiting bacterial cell wall synthesis, leading to the destruction of susceptible bacteria. It is effective against a range of Gram-positive and some Gram-negative bacteria. Amoxicillin is available in various forms, including capsules, tablets, chewable tablets, and oral suspensions. (Learn more on DoseMed)

Indications and Uses

Amoxicillin is indicated for the treatment of infections caused by susceptible strains of designated microorganisms. These include:

Upper Respiratory Tract Infections: Such as infections of the ear, nose, and throat.
Genitourinary Tract Infections: Including infections caused by Escherichia coli, Proteus mirabilis, and Enterococcus faecalis.
Skin and Skin Structure Infections: Caused by susceptible strains of Streptococcus and Staphylococcus species.
Lower Respiratory Tract Infections: Including infections caused by Streptococcus pneumoniae and Haemophilus influenzae.
Helicobacter pylori Infection: In combination with other medications for the treatment of H. pylori infection and duodenal ulcer disease in adults.

Dosage and Administration

Dosage of amoxicillin varies based on the type and severity of infection, as well as patient age and weight. General guidelines include:

Adults: 750 to 1750 mg per day, divided every 8 to 12 hours.
Pediatric Patients over 3 Months: 20 to 45 mg/kg/day, divided every 8 to 12 hours.
Neonates and Infants ≤3 Months: Up to 30 mg/kg/day, divided every 12 hours.

For H. pylori eradication in adults, amoxicillin is used in combination therapies:

Triple Therapy: 1 gram amoxicillin, 500 mg clarithromycin, and 30 mg lansoprazole, all given twice daily for 14 days.
Dual Therapy: 1 gram amoxicillin and 30 mg lansoprazole, each given three times daily for 14 days.

In patients with severe renal impairment (GFR <30 mL/min), dosage adjustments are necessary.

Dosage Forms and Strengths

Amoxicillin is available in the following oral suspension strengths:

125 mg/5 mL
250 mg/5 mL

Each 5 mL of reconstituted suspension contains the specified amount of amoxicillin as the trihydrate.

Contraindications

Amoxicillin is contraindicated in patients with a history of serious hypersensitivity reactions (e.g., anaphylaxis or Stevens-Johnson syndrome) to amoxicillin or other beta-lactam antibiotics, including penicillins and cephalosporins.

Warnings and Precautions

Serious and occasionally fatal hypersensitivity reactions have been reported in patients on penicillin therapy, including amoxicillin. These reactions are more likely in individuals with a history of penicillin hypersensitivity or multiple allergen sensitivities. If an allergic reaction occurs, discontinue amoxicillin and institute appropriate therapy.

Other precautions include:

Severe Cutaneous Adverse Reactions (SCAR): Monitor for skin reactions; discontinue if rash progresses.
Drug-Induced Enterocolitis Syndrome (DIES): If symptoms occur, discontinue amoxicillin and provide appropriate therapy.
Clostridioides difficile-Associated Diarrhea (CDAD): Evaluate patients if diarrhea occurs during or after therapy.

Adverse Reactions

Common adverse reactions (≥1%) observed in clinical trials include:

Diarrhea
Rash
Vomiting
Nausea

Patients should be advised to report any severe or persistent adverse effects to their healthcare provider.

Drug Interactions

Notable drug interactions with amoxicillin include:

Probenecid: May increase amoxicillin levels; coadministration is not recommended.
Oral Anticoagulants: Concomitant use may increase the prolongation of prothrombin time.
Allopurinol: Concurrent use may increase the risk of rash
Oral Contraceptives: Amoxicillin may reduce the efficacy of oral contraceptives.

Patient Counseling Information

Patients should be advised on the following:

Administration: Amoxicillin can be taken every 8 or 12 hours, depending on the prescribed dose.
Allergic Reactions: Inform healthcare providers of any history of allergies to penicillin or other antibiotics.
Diarrhea: Inform patients that diarrhea is a common side effect; however, if it is severe or persistent, they should contact their healthcare provider.
Antibacterial Resistance: Emphasize the importance of completing the full course of therapy to prevent resistance.
Storage: Refrigeration of the suspension is preferable but not required; shake well before each use and discard any unused portion after 14 days.

Conclusion

Amoxicillin is a versatile and widely used antibiotic effective against various bacterial infections. Proper usage, adherence to prescribed dosing, and awareness of potential side effects are essential for optimal treatment outcomes. Patients should consult their healthcare providers with any questions or concerns regarding amoxicillin therapy.

For more detailed information, please refer to the official drug label on DailyMed