Ampicillin is a widely used beta-lactam antibiotic from the aminopenicillin subclass, known for its ability to combat a broad range of bacterial infections. It operates by disrupting the integrity of bacterial cell walls, ultimately leading to bacterial death.
Ampicillin Overview
How It Works
Ampicillin exerts its antibacterial effect by targeting penicillin-binding proteins (PBPs) found in bacterial cell membranes. It specifically inhibits the final stage of peptidoglycan synthesis, a vital process in bacterial cell wall formation. This interference weakens the bacterial cell wall, causing it to rupture.
Antibacterial Spectrum
Ampicillin is effective against a broad array of bacteria, though its efficacy is dependent on bacterial resistance mechanisms.
- Effective Against:
- Gram-positive bacteria: Including Streptococcus species and Enterococcus faecalis
- Gram-negative bacteria: Such as Escherichia coli, Haemophilus influenzae, and Proteus mirabilis
- Limited By:
- Beta-lactamase production: Some bacteria produce enzymes that degrade ampicillin, rendering it ineffective. In such cases, it’s often paired with a beta-lactamase inhibitor like sulbactam.
Clinical Uses
- Respiratory tract infections (e.g., bronchitis, pneumonia)
- Urinary tract infections (UTIs) (e.g., cystitis, pyelonephritis)
- Gastrointestinal infections (e.g., Salmonella, Shigella)
- Meningitis in neonates caused by susceptible pathogens
- Sepsis and systemic bacterial infections
Routes of Administration
- Oral: As capsules or liquid suspension for mild to moderate infections
- Parenteral (IV/IM): For severe infections or when oral intake isn’t feasible
Side Effects
- Common:
- Nausea, vomiting, and diarrhea
- Mild skin rashes
- Less Common:
- Severe allergic reactions, including anaphylaxis in penicillin-sensitive individuals
- Secondary infections: Overgrowth of fungi like Candida may occur with prolonged use
Important Considerations
- Resistance:
- Some pathogens produce beta-lactamase enzymes that inactivate ampicillin
- Resistance testing is often necessary to confirm susceptibility
- Precautions:
- Avoid use in patients with penicillin allergies
- Adjust dosage in those with kidney impairment
- Use during pregnancy and breastfeeding only under medical supervision
- Drug Interactions:
- Probenecid can raise ampicillin levels by reducing excretion
- Oral contraceptives may become less effective with concurrent ampicillin use
Conclusion
Ampicillin remains a valuable treatment option for a range of infections, especially when guided by microbial culture and sensitivity testing. Despite growing resistance, its effectiveness can be preserved through judicious use and combination with beta-lactamase inhibitors when needed.