Short-term nalidixic acid plus sodium citrate in acute lower urinary tract infection.

Low-dose nalidixic acid (0.66 g) in combination with 4 g of sodium citrate (NAC) was evaluated in acute lower UTI. In college-age females (n = 24) given NAC every 8 h for 3 days the nalidixic acid (NA) susceptible infecting strain was eradicated in 100% of the patients and recurrence during the 1 month follow-up period occurred in 1 case (5%) classified as relapse. In a following study the corresponding rates in general practice (GP) patients (n = 71) were 90% and 17%, respectively, irrespective of treatment with NAC every 12 h for 3 days or 5 days. The failures observed in GP were due to persistence of (or immediate reinfection by) the original infecting strain (4%) or its NA resistant mutant (6%). Emergence of NA resistance was associated with high age of the patient and a high incidence of NA resistant mutants in the infecting Escherichia coli strain. NA susceptible failure and recurrence during follow-up occurred primarily in younger GP patients. The recurrences were equally often classified as relapse (6 cases) as reinfection (5 cases). About 20% of the patients reported rather innocuous transient side effects of NAC and interruption of medication occurred in 1 case (0.6%).