Amoxicllin

# Amoxicillin ## Overview - **Classification**: Penicillin antibiotic, Beta-lactam. - **Mechanism**: Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to bacterial cell lysis. ## Primary Indications 1. **Acute Otitis Media**: Bacterial infection of the middle ear. 2. **Streptococcal Pharyngitis**: Group A Streptococcus (GAS) throat infection. 3. **Bacterial Sinusitis**: Acute bacterial rhinosinusitis. 4. **Lower Respiratory Tract Infections**: Exacerbations of chronic bronchitis, community-acquired pneumonia. 5. **H. pylori Eradication**: As part of multi-drug regimens for peptic ulcer disease. 6. **Infective Endocarditis Prophylaxis**: Prevention before certain dental procedures. ## Adult Dosing ### Standard Dosing **Acute Otitis Media, Sinusitis, LRTI (mild-moderate)** - **Dose**: **500 mg** - **Frequency**: Every **8 hours** (TID) - **Route**: Oral - **Duration**: 5-10 days **Severe Infections or H. influenzae suspected (e.g., severe sinusitis)** - **Dose**: **875 mg** - **Frequency**: Every **12 hours** (BID) - **Route**: Oral - **Duration**: 7-10 days **Streptococcal Pharyngitis** - **Dose**: **500 mg** - **Frequency**: Every **12 hours** (BID) - **Route**: Oral - **Duration**: **10 days** (crucial for rheumatic fever prevention) **H. pylori Eradication** - **Dose**: **1000 mg** - **Frequency**: Every **12 hours** (BID) - **Route**: Oral - **Duration**: 14 days (as part of multi-drug regimen) **Infective Endocarditis Prophylaxis (Dental Procedures)** - **Dose**: **2000 mg** (**2g**) - **Frequency**: Single dose - **Route**: Oral - **Duration**: 30-60 minutes before procedure ### Dose Adjustments - **Renal Impairment**: - **CrCl >30 mL/min**: No adjustment. - **CrCl 10-30 mL/min**: **250-500 mg** every **12 hours**. - **CrCl <10 mL/min**: **250-500 mg** every **24 hours**. - **Hemodialysis**: Administer dose after dialysis. - **Hepatic Impairment**: No specific dose adjustment generally required. - **Elderly Patients**: Adjust based on renal function; monitor for adverse effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **20-40 mg/kg/day** - **Frequency**: Divided every **8-12 hours** - **Maximum**: Not typically specified as a fixed mg maximum. - **Special Notes**: Use with caution due to immature renal function; lower doses (20-30 mg/kg/day) for mild infections. ### Infants (1-12 months) - **Dose**: **25-50 mg/kg/day** (standard) - **Frequency**: Divided every **8-12 hours** (TID or BID) - **Maximum**: **1500 mg/day** (for standard dosing). - **Special Notes**: For AOM (high-dose amoxicillin): **80-90 mg/kg/day** divided every **12 hours**. Max **4000 mg/day**. ### Children (1-12 years) - **Dose**: **25-50 mg/kg/day** (standard) - **Frequency**: Divided every **8-12 hours** (TID or BID) - **Maximum**: **1500 mg/day** (for standard dosing). - **Special Notes**: For AOM (high-dose amoxicillin): **80-90 mg/kg/day** divided every **12 hours**. Max **4000 mg/day**. ### Adolescents (13-18 years) - **Dose**: Generally follow **adult dosing** guidelines. - **Maximum**: **4000 mg/day** (4g) oral. ## Safety Information ### Contraindications - **Absolute**: Known **hypersensitivity** to amoxicillin or other penicillins. - **Absolute**: History of **severe hypersensitivity** (e.g., anaphylaxis, SJS) to any beta-lactam antibiotic. - **Relative**: History of **infectious mononucleosis** (increased risk of maculopapular rash). ### Common Adverse Effects - **Very Common (>10%)**: Diarrhea, Nausea. - **Common (1-10%)**: Rash (non-allergic), Vomiting, Abdominal pain. - **Serious but Rare**: Anaphylaxis, Stevens-Johnson syndrome (SJS), Toxic Epidermal Necrolysis (TEN), Clostridioides difficile-associated diarrhea (CDAD), Drug-induced liver injury, Agranulocytosis, Hemolytic anemia. ### Key Drug Interactions - **Allopurinol**: Increased incidence of non-allergic maculopapular rash with amoxicillin. - **Methotrexate**: Amoxicillin may decrease renal clearance of methotrexate, increasing toxicity. Monitor methotrexate levels. - **Warfarin**: May enhance anticoagulant effect by altering gut flora; monitor INR closely. - **Oral Contraceptives**: May reduce efficacy due to altered gut flora; advise backup contraception. - **Probenecid**: Decreases renal tubular secretion of amoxicillin, increasing and prolonging amoxicillin plasma levels. ## Monitoring & Follow-up - **Before Treatment**: Assess for any history of penicillin or beta-lactam allergies. - **During Treatment**: Monitor for signs of allergic reaction (rash, urticaria, angioedema) or severe diarrhea (CDAD). - **Clinical Signs**: Assess resolution of infection symptoms (e.g., fever, pain, cough). ## Clinical Pearls - 💡 **Tip 1**: Amoxicillin can be taken with or without food. Taking it with food may help reduce GI upset. - 💡 **Tip 2**: For streptococcal pharyngitis, completing the full **10-day course** is essential to prevent acute rheumatic fever. - 💡 **Tip 3**: Differentiate a non-allergic maculopapular rash (common, especially with mononucleosis) from a true allergic reaction. - 💡 **Tip 4**: Oral suspensions must be **refrigerated** and shaken well before each use. Discard unused portion after 14 days. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.