Ampicillin Medical Uses and Mechansim of Action

Ampicillin is an antibiotic belonging to the penicillin family of class aminopenicillin. Ampicillin is a medication used to treat certain bacterial infections like those from S. pneumoniae, E. coli and H. influenzae etc, it is also used to treat respiratory tract infections, meningitis and urinary tract infections. It is resistant to acid so it can be taken orally, by injection into a muscle, or intravenously.

Ampicillin is in a class of medications called penicillin. It is chemically described as (2S,5R,6R)-6-((R)-2-amino-2-phenylacetamido)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0] heptane-2-carboxylic acid. Its molecular formula is C16H19N3O4S and its molecular weight is 349.40 g/mol. It was discovered in 1958 and came into commercial use in 1961.The World Health Organization classifies ampicillin as critically important for human medicine. 

It is used to treat infections by many gram-positive and gram-negative bacteria. It was the first "broad spectrum" penicillin with activity against gram-positive bacteria, including Streptococcus pneumoniae, Streptococcus pyogenes. Activity against gram-negative bacteria includes Neisseria meningitidis, Haemophilus influenzae. Ampicillin is used to treat certain infections that are caused by bacteria such as meningitis (infection of the membranes that surround the brain and spinal cord); and infections of the throat, sinuses, lungs, reproductive organs, urinary tract, and gastrointestinal tract.

The dosage forms available for ampicillin include oral capsules or liquid suspensions. There is also a powder that can be made into an injection form. Capsule- 250 / 500mg, Oral suspension- 125/ 250mg, Powder: 125mg, 250mg, 500mg.

MECHANSIM OF ACTION: Ampicillin is a beta-lactam antibiotic and is classified as aminopenicillins.

The mode of action of beta-lactam antimicrobials on sensitive organisms can be considered a two-step process:

1. In the first step, the drug binds to primary receptors called membrane-bound penicillin-binding proteins (PBPs). These proteins perform vital roles in cell cycle-related; formation of cell wall peptidoglycan structure. Therefore, the inactivation of PBPs by bound antimicrobials immediately affects their function.
2. The second stage comprises the physiological effects caused by this receptor-ligand interaction. PBPs are involved in the cell wall's late stages of peptidoglycan synthesis. Because peptidoglycan maintains the integrity of the cell wall, which resides in a hypotonic environment, its disruption causes lysis and cell death. 

It is important to recognize that ampicillin is primarily bactericidal against susceptible bacteria due to its inhibition of cell wall synthesis.Penicillinase (a Beta-lactamase) cleaves the beta-lactam ring and results in resistance to ampicillin. Hence ampicillin is usually combined with ?-lactamase inhibitors like sulbactam.

Ampicillin is often used to treat urinary infections with Gram-negative enteric bacterial etiologies. The drug is also used to treat respiratory tract infections. Additionally ampicillin is uniformly effective against group B Streptococcus, but is ineffective against Enterobacter, Hemophilus influenzae, Pseudomonas and indole positive Proteus infections, It's a combination of a β-lactam antibiotic and a β-lactamase inhibitor. It works by binding to penicillin-binding proteins to inhibit bacterial cell wall synthesis. Due to this disruption of the bacterial cell wall takes place which ultimately leads to bacterial cell death.

Ampicillin also acts as inhibitor for the enzyme transpeptidase, which is required to make bacterial cell walls. It inhibits the synthesis of bacterial cell wall in binary fission, and causes cell lysis.It has received FDA approval for its mechanism of action.

Medical Uses:

It works by stopping the growth of bacteria. This antibiotic treats only bacterial infections. Ampicillin is used to treat following Diseases.

Respiratory infections: Such as bronchitis and pharyngitis.

Bacterial meningitis: which are caused by the Haemophilus influenzae and Streptococcus pneumoniae.

Gastrointestinal infections: which are caused due to consumption of contaminated water or food for eg. Salmonella.

Other uses: Injection of Ampicillin is used to prevent passing of infection to the baby during birth in some pregnant women.

Common side effects:

The most common side effects of amoxicillin include fever, diarrhea, vomiting, nausea, weakness or tiredness and allergic reactions like skin rash, swelling of the face, lips, or tongue, breathing problems.

Some of the impurities of Ampicillin are-

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