Amoxicillin Drug Profile

What is Amoxicillin?

Amoxicillin is a broad-spectrum antibiotic that belongs to the penicillin class of medications. It is one of the most commonly prescribed antibiotics worldwide and is used to treat a wide variety of bacterial infections. This medication works by killing bacteria or preventing their growth, making it effective against many gram-positive and some gram-negative bacterial strains.

Uses

Amoxicillin is prescribed for numerous bacterial infections, including:

• Respiratory tract infections: Including pneumonia, bronchitis, sinusitis, and strep throat caused by susceptible bacteria
• Ear infections: Both middle ear infections (otitis media) and outer ear infections in children and adults
• Urinary tract infections: Including bladder infections and kidney infections caused by sensitive bacterial strains
• Skin and soft tissue infections: Such as cellulitis, wound infections, and infected cuts or abrasions
• Dental infections: Including tooth abscesses and periodontal infections
• Helicobacter pylori eradication: Used in combination therapy to treat stomach ulcers caused by H. pylori bacteria

How it works

Amoxicillin works by interfering with bacterial cell wall synthesis, specifically targeting enzymes called penicillin-binding proteins that are essential for building and maintaining the bacterial cell wall. When these proteins are inhibited, the bacterial cell wall becomes weak and eventually ruptures, leading to bacterial death. This mechanism makes amoxicillin bactericidal, meaning it actively kills bacteria rather than just stopping their growth.

Side effects

Common side effects include:

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• Nausea and vomiting
• Diarrhea
• Abdominal cramping
• Skin rash
• Headache
• Dizziness
• Vaginal yeast infections
• Changes in taste

Serious side effects requiring immediate medical attention:

• Severe allergic reactions (anaphylaxis) with difficulty breathing, swelling of face or throat
• Clostridioides difficile-associated diarrhea (severe, persistent, bloody diarrhea)
• Severe skin reactions including Stevens-Johnson syndrome
• Liver dysfunction with yellowing of skin or eyes
• Severe abdominal pain with cramping

Warnings and precautions

• Allergy history: Patients with known allergies to penicillin, cephalosporins, or other beta-lactam antibiotics should avoid amoxicillin due to risk of cross-reactivity
• Pregnancy and breastfeeding: Generally considered safe during pregnancy (FDA Pregnancy Category B) and breastfeeding, but should only be used when clearly needed under medical supervision
• Kidney impairment: Dosage adjustments may be necessary in patients with significant kidney dysfunction as the drug is primarily eliminated through the kidneys
• Infectious mononucleosis: Patients with mono who take amoxicillin have a high risk of developing a characteristic skin rash
• Antibiotic resistance: Complete the full prescribed course even if symptoms improve to prevent development of resistant bacteria

Interactions

• Oral contraceptives: May reduce effectiveness of birth control pills, requiring additional contraceptive methods
• Warfarin: Can enhance anticoagulant effects, increasing bleeding risk and requiring more frequent INR monitoring
• Methotrexate: Amoxicillin may increase methotrexate levels, potentially leading to toxicity
• Allopurinol: Concurrent use increases risk of skin rash development
• Probenecid: Blocks kidney elimination of amoxicillin, leading to higher and prolonged blood levels
• Live bacterial vaccines: Antibiotics may reduce effectiveness of live vaccines like typhoid vaccine
• Chloramphenicol: May antagonize the bactericidal effects of amoxicillin
• Probiotics: Should be taken at least 2 hours apart from amoxicillin to maintain beneficial bacterial effectiveness

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Dosage

Typical adult dosages vary depending on the type and severity of infection:

• Mild to moderate infections: 250-500 mg every 8 hours or 500-875 mg every 12 hours
• Severe infections: 875 mg every 12 hours or 500 mg every 8 hours
• H. pylori eradication: 1000 mg twice daily as part of combination therapy
• Treatment duration: Typically 7-10 days, though some infections may require shorter or longer courses

Dosage should always be determined by a healthcare provider based on the specific infection, patient weight, kidney function, and other individual factors. Pediatric dosing is weight-based and requires careful calculation by a healthcare professional.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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