ampisillin

Ampicillin, sometimes misspelled as ampisillin, is a beta-lactam antibiotic in the penicillin family. It is a semi-synthetic broad‑spectrum penicillin used to treat infections caused by susceptible bacteria.

The drug works by inhibiting bacterial cell-wall synthesis. It binds to penicillin-binding proteins, disrupting transpeptidation and cross-linking of peptidoglycan, which leads to bacterial lysis. Ampicillin is generally bactericidal and is active against a range of organisms, though activity is reduced against beta-lactamase–producing strains.

Spectrum and uses: Ampicillin is effective against many Gram-positive cocci, including Streptococcus species and Enterococcus faecalis, as well as certain Gram-negative organisms such as Escherichia coli, Haemophilus influenzae, Proteus mirabilis, Salmonella, and Shigella. It has limited activity against Pseudomonas aeruginosa and other non-susceptible bacteria. To broaden coverage or overcome resistance, it is sometimes given with a beta-lactamase inhibitor (for example ampicillin-sulbactam).

Administration and pharmacokinetics: Ampicillin can be given orally or by injection (intravenous or intramuscular). It is distributed through body tissues and fluids and is eliminated primarily by the kidneys, so dose adjustments are needed in renal impairment. It can reach therapeutic levels in most tissues, including cerebrospinal fluid when meninges are inflamed.

Adverse effects and resistance: Common adverse effects include allergic reactions, rash, diarrhea, and superinfections. Rash can occur with concurrent allopurinol use. Resistance often stems from beta-lactamase production; combinations with beta-lactamase inhibitors or alternative agents are used in resistant infections.