Drug General Information (ID: DDIW4D1L28)
Drug Name			Nalidixic acid		Drug Info		Probenecid		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antibiotics				Uricosuric Agents
Structure

Mechanism of Nalidixic acid-Probenecid Interaction (Severity Level: Moderate)
Competitive inhibition of renal tubular secretion Click to Show/Hide Mechanism Graph
Drug Name		Nalidixic acid				Probenecid
Mechanism		Nalidixic acid				Competitive inhibition of renal tubular secretion of nalidixic acid
Key Mechanism Factor 1
		Factor Name		Renal tubular secretion
		Factor Description		Renal tubular secretion allows selective transfer of substances from the blood around the capillaries into the renal tubules via filtrate. Drug excretion may be reduced when two drugs compete for renal tubular secretion.
Mechanism Description		Decreased elimination of Nalidixic acid caused by Probenecid mediated competitive inhibition of renal tubular secretion

Recommended Action
Management		alternatives to nalidixic acid should preferably be considered for the treatment of urinary tract infections in patients receiving probenecid. Nitrofurantoin and sulfamethoxazole-trimethoprim have not been reported to interact with probenecid and may be suitable choices depending on organism susceptibility.

References
1	Dash H, Mills J "Letter: Severe metabolic acidosis associated with nalidixic acid overdose." Ann Intern Med 84 (1976): 570-1. [PMID: 1275361]
2	Product Information. NegGram (nalidixic acid). Sanofi Winthrop Pharmaceuticals, New York, NY.