Ampicillin is a broad-spectrum aminopenicillin antibiotic belonging to the beta-lactam class, widely utilized in clinical practice for its efficacy against a diverse range of gram-positive and gram-negative bacteria. It functions by inhibiting bacterial cell wall synthesis, leading to osmotic instability and cell lysis. This bactericidal agent is particularly valuable for 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 targeted antimicrobial therapy, balancing potency with a well-characterized safety profile.

Features

• Broad-spectrum activity against gram-positive and gram-negative bacteria
• Bactericidal mechanism via inhibition of cell wall synthesis
• Available in oral (capsules, suspension) and intravenous/intramuscular formulations
• Acid-stable for reliable oral absorption
• Synergistic activity with beta-lactamase inhibitors (e.g., sulbactam)
• Well-established pharmacokinetic profile with good tissue penetration

Benefits

• Effectively treats a wide variety of bacterial infections, reducing the need for multiple antibiotics
• Rapid bactericidal action promotes quicker symptom resolution and shorter infection duration
• Suitable for both community-acquired and hospital-acquired infections when susceptibility is confirmed
• Oral formulation allows for convenient outpatient treatment and improved compliance
• Generally well-tolerated with a long history of clinical use and safety data
• Cost-effective compared to many newer broad-spectrum alternatives

Common use

Ampicillin is commonly prescribed for infections caused by susceptible strains of bacteria, including:

• Respiratory tract infections (e.g., bronchitis, pneumonia caused by Haemophilus influenzae, Streptococcus pneumoniae)
• Urinary tract infections (e.g., Escherichia coli, Proteus mirabilis, Enterococcus species)
• Gastrointestinal infections (e.g., Salmonella typhi, Shigella species)
• Meningitis (particularly in neonates and children, often in combination with other antibiotics)
• Septicemia and endocarditis (especially caused by Enterococcus faecalis)
• Otitis media and sinusitis in pediatric populations

Dosage and direction

Dosage varies based on infection severity, patient age, renal function, and route of administration. Typical adult doses range from 250–500 mg orally every 6 hours, or 1–2 g intravenously/intramuscularly every 4–6 hours for severe infections. Pediatric dosing is weight-based, generally 50–100 mg/kg/day in divided doses. For meningitis, higher doses (up to 200–400 mg/kg/day IV in children) may be used. Always complete the full course of therapy even if symptoms improve earlier. Take oral ampicillin on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption.

Precautions

• Use with caution in patients with mononucleosis due to increased risk of rash
• Monitor renal and hepatic function during prolonged therapy
• May cause false-positive urine glucose tests with Benedict’s or Fehling’s solutions
• Superinfection with fungi or resistant bacteria may occur
• Avoid in patients with history of hypersensitivity to penicillins or other beta-lactams
• Use during pregnancy only if clearly needed (Category B)

Contraindications

• Hypersensitivity to ampicillin, other penicillins, or beta-lactam antibiotics
• Previous history of ampicillin-associated hepatitis or cholestatic jaundice
• Infectious mononucleosis (due to high incidence of rash)
• Concomitant use with bacteriostatic antibiotics in critical infections

Possible side effect

Common side effects include:

• Gastrointestinal disturbances (nausea, vomiting, diarrhea)
• Skin rash (maculopapular or urticarial)
• Candidiasis (oral or vaginal)

Less common but serious side effects:

• Hypersensitivity reactions (anaphylaxis, angioedema)
• Clostridium difficile-associated diarrhea
• Hematologic abnormalities (leukopenia, thrombocytopenia)
• Hepatitis or elevated liver enzymes
• Interstitial nephritis

Drug interaction

• Probenecid: decreases renal excretion of ampicillin, increasing serum levels
• Allopurinol: increases incidence of skin rash
• Oral contraceptives: reduced efficacy due to altered gut flora
• Warfarin: may potentiate anticoagulant effect
• Bacteriostatic antibiotics (e.g., tetracyclines, chloramphenicol): may antagonize bactericidal effect
• Methotrexate: increased toxicity due to reduced renal clearance

Missed dose

If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. Do not double the dose to catch up. Maintaining consistent serum levels is important for efficacy, so try to adhere to the prescribed schedule.

Overdose

Ampicillin overdose is rare but may manifest as neuromuscular hypersensitivity, seizures, or electrolyte imbalances. Gastrointestinal symptoms (nausea, vomiting, diarrhea) are common. Management is supportive; hemodialysis may enhance elimination in cases of significant overdose, particularly in renal impairment.

Storage

Store at room temperature (15–30°C) in a dry place. Protect from light and moisture. Keep oral suspension refrigerated after reconstitution and discard after 14 days. Do not freeze. Keep out of reach of children.

Disclaimer

This information is for educational purposes and does not replace professional medical advice. Always consult a healthcare provider for diagnosis, treatment decisions, and personalized dosing. Resistance patterns vary geographically—susceptibility testing is recommended prior to use where possible.

Reviews

Ampicillin has been extensively studied and reviewed over decades of clinical use. It is regarded as a reliable and effective antibiotic for susceptible infections, particularly in settings where resistance is not prevalent. Medical literature consistently supports its role in treating enterococcal infections, Listeria meningitis, and certain community-acquired infections. Drawbacks include increasing resistance due to beta-lactamase production and a higher incidence of rash compared to some other penicillins. Overall, it remains a valuable agent in the antimicrobial arsenal when used appropriately.