Ampicillin (Ampicillin Sodium) - Description and Clinical Pharmacology

For Intramuscular or Intravenous Injection

To reduce the development of drug-resistant bacteria and maintain the effectiveness of ampicillin and other antibacterial drugs, Ampicillin for Injection, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

DESCRIPTION

Ampicillin for Injection, USP the monosodium salt of [2S-[2α,5α,6β(S*)]]-6-[(aminophenylacetyl)amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, is a synthetic penicillin. It is an antibacterial agent with a broad spectrum of bactericidal activity against both penicillin-susceptible Gram-positive organisms and many common Gram-negative pathogens.

It has the following chemical structure:

The molecular formula is C₁₆H₁₈N₃NaO₄S, and the molecular weight is 371.39. Ampicillin for Injection, USP contains 2.9 milliequivalents of sodium per 1 gram of drug. Each vial contains ampicillin sodium equivalent to 125 mg, 250 mg, 500 mg, 1 gram or 2 grams ampicillin.

CLINICAL PHARMACOLOGY

Ampicillin for Injection, USP diffuses readily into most body tissues and fluids. However, penetration into the cerebrospinal fluid and brain occurs only when the meninges are inflamed. Ampicillin is excreted largely unchanged in the urine and its excretion can be delayed by concurrent administration of probenecid. The active form appears in the bile in higher concentrations than those found in serum. Ampicillin is the least serum-bound of all the penicillins, averaging about 20% compared to approximately 60 to 90% for other penicillins. Ampicillin for Injection, USP is well tolerated by most patients and has been given in doses of 2 grams daily for many weeks without adverse reactions.

Microbiology

While in vitro studies have demonstrated the susceptibility of most strains of the following organisms, clinical efficacy for infections other than those included in the INDICATIONS AND USAGE section has not been demonstrated.

The following bacteria have been shown in in vitro studies to be susceptible to Ampicillin for Injection, USP:

GRAM-POSITIVE ORGANISMS: Hemolytic and nonhemolytic streptococci, D. pneumoniae , nonpenicillinase-producing staphylococci, Clostridia spp., B. anthracis , Listeria monocytogenes , and most strains of enterococci.

GRAM-NEGATIVE ORGANISMS: H. influenzae , N. gonorrhoeae , N. meningitidis , Proteus mirabilis, and many strains of Salmonella, Shigella, and E. coli.

AMPICILLIN does not resist destruction by penicillinase.

Susceptibility Tests

Ampicillin Susceptibility Test Discs, 10 mcg, should be used to estimate the in vitro susceptibility of bacteria to Ampicillin for Injection, USP.