ampicillin + cloxacillin + gentamicin

This is a combination of three antibiotics—ampicillin, cloxacillin, and gentamicin—used primarily for the treatment of severe bacterial infections such as neonatal and pediatric sepsis.

• Ampicillin is a broad-spectrum beta-lactam antibiotic effective against many Gram-positive and some Gram-negative bacteria by inhibiting bacterial cell wall synthesis.
• Cloxacillin is a penicillinase-resistant beta-lactam antibiotic mainly active against penicillinase-producing staphylococci (notably Staphylococcus aureus), also acting via inhibition of cell wall synthesis.
• Gentamicin is an aminoglycoside antibiotic with bactericidal activity, particularly potent against aerobic Gram-negative bacteria; it binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibition of protein synthesis.

The combination provides broad-spectrum coverage:

• Ampicillin covers Listeria monocytogenes and many enteric Gram-negatives.
• Cloxacillin adds robust anti-staphylococcal activity.
• Gentamicin offers synergy with beta-lactams for both Gram-positive (including Enterococcus) and Gram-negative pathogens.

This regimen is commonly used in resource-limited settings for neonatal sepsis or suspected mixed infections where both staphylococci (including resistant strains) and other community-acquired pathogens are likely. The fixed-dose combination formulation has been widely used in some countries but lacks regulatory approval from major agencies like the US FDA or EMA due to concerns about rationality, efficacy data, and antimicrobial resistance.