Amoxicillin: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
Amoxicillin: clinical details
Prescribing considerations
- Confirm the nature and timing of previous penicillin, cephalosporin or other beta-lactam reactions.
- Base selection on infection site and severity, likely pathogens, susceptibility and local antimicrobial policy.
- Review renal function and relevant seizure risk; impaired renal clearance increases exposure and convulsion risk.
- Avoid amoxicillin when infectious mononucleosis is suspected because a morbilliform rash is strongly associated.
- For parenteral treatment, consider sodium burden, hydration, urine output, catheter patency and product compatibility.
Contraindications and cautions
- Hypersensitivity to amoxicillin, any penicillin or a relevant product excipient.
- Previous severe immediate hypersensitivity reaction, such as anaphylaxis, to another beta-lactam antibiotic.
Monitoring
- Renal function where impairment is present or prolonged treatment is planned.
- Hepatic function in hepatic impairment and periodically during prolonged treatment.
- Full blood count and broader organ-system assessment during prolonged treatment.
- INR or prothrombin time with oral anticoagulants.
- Urine output and catheter patency where crystalluria risk is clinically relevant.
Clinical pharmacology
Amoxicillin is a semisynthetic aminopenicillin that inhibits bacterial cell-wall synthesis. Oral bioavailability is about 70%, food does not materially reduce absorption, protein binding is low, and elimination is predominantly renal. Clearance falls with declining renal function, and haemodialysis removes amoxicillin.
Formulation and product differences
- Selected oral products contain amoxicillin trihydrate; the injectable product contains amoxicillin sodium.
- Suspensions require reconstitution and shaking. Storage requirements and excipients vary between products.
- The selected injection vial contributes sodium and has specific compatibility requirements. It must not be mixed with aminoglycosides in the same syringe, container or administration set.
Amoxicillin preparations and strengths
Capsule
Route: Oral
Strengths: 250 mg, 500 mg
Oral suspension
Route: Oral
Strengths: 125 mg/5 mL, 250 mg/5 mL, 500 mg/5 mL
Amoxicillin interactions
Tell the prescriber or pharmacist about all prescription, over-the-counter and complementary medicines. Important examples include:
Methotrexate
Penicillins can reduce its renal clearance and increase toxicity risk; clinical review and monitoring may be needed.
Warfarin and other oral anticoagulants
Anticoagulant effect and INR may change, so additional clotting monitoring may be required when amoxicillin is started or stopped.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.