Indications
Nalidixic Acid is primarily indicated for the treatment of urinary tract infections attributable to susceptible gram-negative microorganisms. Specifically, it is effective against a majority of Escherichia coli strains, as well as Enterobacter, Klebsiella, and Proteus species. This specificity makes it a suitable option for managing infections in cases where these bacterial strains are identified as the causative agents.
Pharmacodynamics
As a member of the quinolone class of antibacterial agents, Nalidixic Acid demonstrates significant antibacterial activity against gram-negative bacteria, which include Enterobacter species, Escherichia coli, Morganella morganii, Proteus mirabilis, Proteus vulgaris, and Providencia rettgeri. Notably, Pseudomonas species generally exhibit resistance to this drug. Nalidixic Acid functions as a bactericidal agent and maintains its efficacy across the complete urinary pH spectrum. Chromosomal resistance has been documented to develop in approximately 2 to 14 percent of patients receiving full dosage, although this resistance is not known to be r-factor transferable.
Absorption
When administered orally, Nalidixic Acid is rapidly absorbed through the gastrointestinal tract, with a bioavailability of approximately 96%. The presence of antacids can delay its absorption. This efficient absorption profile supports its prompt onset of action in treating urinary tract infections.
Metabolism
The drug undergoes hepatic metabolism, where about 30% of the administered dose is converted into its active metabolite, hydroxynalidixic acid. The parent drug and its active metabolite are rapidly conjugated into inactive metabolites. There is significant variability in metabolism among individuals. In urinary excretion, hydroxynalidixic acid accounts for 80 to 85% of the drug's antibacterial activity, underscoring its significant role in exerting therapeutic effects.
Mechanism of Action
Nalidixic Acid operates by means of its active metabolite, hydroxynalidixic acid, which exhibits a strong yet reversible binding affinity to DNA. This interaction disrupts RNA synthesis and subsequently hinders protein synthesis. By interfering with these essential biological processes, Nalidixic Acid effectively impedes bacterial growth and proliferation.
