Ampicillin

# Ampicillin ## Overview - **Classification**: Penicillin antibiotic, Beta-lactam antibiotic - **Mechanism**: Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and bacterial death. ## Primary Indications 1. **Susceptible Infections**: Respiratory, gastrointestinal, genitourinary, skin/soft tissue infections. 2. **Meningitis**: Treatment of bacterial meningitis caused by susceptible organisms (e.g., *Listeria monocytogenes*, *Neisseria meningitidis*). 3. **Listeriosis**: Treatment of *Listeria monocytogenes* infections, including bacteremia and endocarditis. 4. **Endocarditis Prophylaxis**: Prevention of bacterial endocarditis in high-risk patients undergoing certain procedures. ## Adult Dosing ### Standard Dosing **General Susceptible Infections (e.g., RTI, UTI, Skin/Soft Tissue)** - **Dose**: **250-500 mg** - **Frequency**: Every **6 hours** - **Route**: PO, IV, or IM - **Maximum**: Usually **2-4 g/day** **Bacterial Meningitis / Severe Systemic Infections (e.g., Listeriosis)** - **Dose**: **2 g** - **Frequency**: Every **4 hours** - **Route**: IV - **Maximum**: **12-14 g/day** **Endocarditis Prophylaxis (Dental/Respiratory Procedures)** - **Dose**: **2 g** - **Frequency**: Single dose **30-60 minutes** prior to procedure - **Route**: IV or IM ### Dose Adjustments - **Renal Impairment**: - **CrCl 10-50 mL/min**: Administer standard dose every **6-12 hours**. - **CrCl <10 mL/min**: Administer standard dose every **12-24 hours**. - **Hemodialysis**: Administer dose after dialysis. - **Hepatic Impairment**: No specific dose adjustment generally needed. - **Elderly Patients**: Adjust dose based on renal function due to age-related decline. ## Pediatric Dosing ### Neonates (0-28 days) - **Indications**: Meningitis, sepsis, *Listeria* infections. - **Age <7 days & <2000 g**: - **Dose**: **50-100 mg/kg/dose** - **Frequency**: Every **12 hours** - **Route**: IV - **Age <7 days & >2000 g**: - **Dose**: **50-100 mg/kg/dose** - **Frequency**: Every **8 hours** - **Route**: IV - **Age 7-28 days & <2000 g**: - **Dose**: **50-100 mg/kg/dose** - **Frequency**: Every **8 hours** - **Route**: IV - **Age 7-28 days & >2000 g**: - **Dose**: **50-100 mg/kg/dose** - **Frequency**: Every **6 hours** - **Route**: IV - **Maximum**: Up to **400 mg/kg/day** for severe infections (meningitis). - **Special Notes**: Doses may be higher for meningitis; consult institutional guidelines. ### Infants (1-12 months) - **General Infections**: - **Dose**: **50-100 mg/kg/day** divided - **Frequency**: Every **6 hours** - **Route**: IV, IM, PO - **Meningitis / Severe Infections**: - **Dose**: **200-400 mg/kg/day** divided - **Frequency**: Every **4-6 hours** - **Route**: IV - **Maximum**: Up to **12 g/day**. ### Children (1-12 years) - **General Infections**: - **Dose**: **50-100 mg/kg/day** divided - **Frequency**: Every **6 hours** - **Route**: IV, IM, PO - **Meningitis / Severe Infections**: - **Dose**: **200-400 mg/kg/day** divided - **Frequency**: Every **4-6 hours** - **Route**: IV - **Maximum**: **12 g/day** for severe infections; general maximum **4 g/day**. ### Adolescents (13-18 years) - **Dose**: Typically follows **adult dosing guidelines**. - **Maximum**: Adult maximums apply (e.g., **12-14 g/day** for severe infections). ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to ampicillin or other penicillins. - **Absolute**: History of severe hypersensitivity to other beta-lactam antibiotics (e.g., cephalosporins, carbapenems). ### Common Adverse Effects - **Very Common (>10%)**: Diarrhea (oral), Rash (maculopapular, especially with viral infections like mononucleosis). - **Common (1-10%)**: Nausea, Vomiting, Abdominal pain, Oral candidiasis. - **Serious but Rare**: Anaphylaxis, Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), Clostridioides difficile-associated diarrhea (CDAD), Seizures (high doses in renal impairment), Hemolytic anemia, Interstitial nephritis. ### Key Drug Interactions - **Probenecid**: Decreases renal tubular secretion of ampicillin, increasing ampicillin levels. - **Allopurinol**: Concurrent use significantly increases risk of rash. - **Oral Contraceptives**: May reduce efficacy of estrogen-containing oral contraceptives; consider alternative birth control. - **Tetracyclines**: May antagonize the bactericidal effect of ampicillin. Avoid co-administration. - **Methotrexate**: Ampicillin may decrease methotrexate clearance, increasing toxicity. Monitor closely. ## Monitoring & Follow-up - **Before Treatment**: Assess for penicillin allergy. Obtain cultures and susceptibility tests. - **During Treatment**: - **Renal function**: Periodically monitor CrCl, especially in impaired patients or with prolonged therapy. - **Liver function**: Periodically monitor LFTs with prolonged therapy. - **CBC**: Monitor for signs of bone marrow suppression with prolonged therapy. - **Clinical signs**: Monitor for signs of allergy (rash, pruritus), C. diff-associated diarrhea, or superinfection. - **Clinical Signs**: Resolution of infection symptoms (fever, WBC count, local signs of inflammation). ## Clinical Pearls - 💡 **Administration**: Oral ampicillin should be taken on an **empty stomach** (1 hour before or 2 hours after meals) for optimal absorption. - 💡 **Rash with Mononucleosis**: A non-allergic maculopapular rash is common if ampicillin is given to patients with infectious mononucleosis. - 💡 **Formulations**: Available as oral capsules/suspension and parenteral (IV/IM) for versatility. - 💡 **IV Compatibility**: Check compatibility with other IV medications if co-administering. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.