Ampicillin: Broad-Spectrum Antibiotic for Effective Bacterial Infection Control
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| Product dosage: 500mg | |||
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Synonyms | |||
Ampicillin is a broad-spectrum aminopenicillin antibiotic renowned for its bactericidal activity against a wide range of Gram-positive and Gram-negative organisms. As a beta-lactam antibiotic, it inhibits bacterial cell wall synthesis, leading to osmotic instability and cell death. It is particularly valued in clinical practice for its reliability in treating respiratory, urinary, gastrointestinal, and meningeal infections, especially when susceptibility is confirmed. Available in oral and parenteral formulations, ampicillin remains a cornerstone in empiric and directed antimicrobial therapy across inpatient and outpatient settings.
Features
- Bactericidal activity against susceptible Gram-positive and Gram-negative bacteria
- Available as capsules (250 mg, 500 mg), oral suspension (125 mg/5 mL, 250 mg/5 mL), and injectable formulations
- Stability in acidic gastric environment allows for effective oral absorption
- Synergistic activity with beta-lactamase inhibitors (e.g., sulbactam) for enhanced spectrum
- Distributed into most body tissues and fluids, including cerebrospinal fluid when meninges are inflamed
Benefits
- Effectively treats a broad range of common and serious bacterial infections
- Rapid onset of action due to bactericidal mechanism
- Well-established safety profile with decades of clinical use
- Suitable for both adult and pediatric populations
- Cost-effective compared to many newer broad-spectrum antibiotics
- Flexible administration routes accommodate various clinical scenarios
Common use
Ampicillin is indicated for the treatment of infections caused by susceptible strains of designated microorganisms, including:
- Respiratory tract infections (e.g., pneumonia, bronchitis) caused by Streptococcus pneumoniae, Haemophilus influenzae, and Streptococcus pyogenes
- Urinary tract infections caused by Escherichia coli, Proteus mirabilis, and Enterococcus species
- Gastrointestinal infections including Salmonella typhosa and other Salmonella species
- Bacterial meningitis caused by Neisseria meningitidis
- Septicemia and endocarditis caused by susceptible organisms
- Prophylaxis of bacterial endocarditis in high-risk patients undergoing dental or surgical procedures
Dosage and direction
Dosage must be individualized based on infection severity, pathogen susceptibility, and patient factors:
Adults:
- Mild to moderate infections: 250-500 mg orally every 6 hours
- Severe infections: 1-2 g IV/IM every 4-6 hours
- Meningitis: 2 g IV every 4 hours
- Endocarditis prophylaxis: 2 g IM/IV 30 minutes before procedure
Children:
- 50-100 mg/kg/day in equally divided doses every 6 hours (oral)
- 100-200 mg/kg/day IV in divided doses every 6 hours for severe infections
- Maximum dose should not exceed adult dosing
Renal impairment: Dosage adjustment required for creatinine clearance below 30 mL/min
Administration guidelines:
- Oral administration: Take on empty stomach (1 hour before or 2 hours after meals) for optimal absorption
- Injectable forms: Reconstitute according to manufacturer instructions; administer IV over 15-30 minutes
- Complete full course of therapy even if symptoms improve
Precautions
- Use with caution in patients with history of hypersensitivity reactions to penicillins, cephalosporins, or other allergens
- Monitor renal, hepatic, and hematopoietic function during prolonged therapy
- May cause antibiotic-associated colitis; evaluate patients who develop diarrhea
- Superinfections with fungi or resistant bacteria may occur
- False-positive urinary glucose tests may occur with copper reduction methods
- Use during pregnancy only if clearly needed (Category B)
- Excreted in breast milk; use with caution in nursing mothers
Contraindications
- History of serious hypersensitivity reaction to ampicillin or other beta-lactam antibiotics
- Infectious mononucleosis due to high incidence of skin rash
- Previous history of ampicillin-associated cholestatic jaundice/hepatic dysfunction
Possible side effect
Common reactions (≥1%):
- Gastrointestinal: diarrhea, nausea, vomiting, glossitis, stomatitis
- Dermatological: rash, urticaria, pruritus
- Hypersensitivity: fever, eosinophilia, serum sickness-like reactions
Serious reactions (<1%):
- Anaphylaxis
- Stevens-Johnson syndrome
- Toxic epidermal necrolysis
- Hepatitis and cholestatic jaundice
- Hemolytic anemia
- Interstitial nephritis
- Seizures (with high doses in renal impairment)
- Pseudomembranous colitis
Drug interaction
- Probenecid: decreases renal tubular secretion of ampicillin, increasing serum levels
- Allopurinol: increased incidence of skin rash
- Oral contraceptives: may decrease efficacy due to altered enterohepatic circulation
- Aminoglycosides: synergistic against some organisms but physically incompatible when mixed
- Warfarin: may potentiate anticoagulant effect
- Bacteriostatic antibiotics: may interfere with bactericidal action
Missed dose
- Take the missed dose as soon as remembered
- If it is almost time for the next dose, skip the missed dose and resume regular schedule
- Do not double doses to make up for missed dose
- Maintain consistent dosing intervals to ensure therapeutic serum levels
Overdose
- Symptoms: primarily neuromuscular hypersensitivity, seizures, electrolyte imbalances
- Management: supportive care including maintenance of airway and hydration
- Hemodialysis may be effective in removing ampicillin
- No specific antidote available
- Contact poison control center for latest guidance
Storage
- Capsules: store at 20-25°C (68-77°F) in tight container
- Oral suspension: reconstituted suspension stable for 14 days at room temperature or refrigerated
- Injectable forms: follow manufacturer’s reconstitution and storage instructions
- Protect from moisture and excessive heat
- Keep out of reach of children
- Do not use beyond expiration date
Disclaimer
This information is for educational purposes only and does not constitute medical advice. Ampicillin is a prescription medication that should be used only under the supervision of a qualified healthcare provider. Dosage and treatment duration must be determined by a physician based on individual patient factors and confirmed bacterial susceptibility. Patients should not self-medicate or adjust dosing without medical consultation. Healthcare providers should reference complete prescribing information before administration.
Reviews
Clinical studies and decades of use demonstrate ampicillin’s efficacy and generally favorable safety profile. In comparative trials, ampicillin shows equivalent efficacy to newer antibiotics for susceptible organisms while maintaining cost advantages. Pediatric formulations are particularly praised for palatability and dosing flexibility. The main limitations noted in clinical experience include increasing bacterial resistance patterns and the need for combination therapy in some settings. Overall, ampicillin remains a valuable therapeutic option when used appropriately based on susceptibility testing and clinical judgment.