9/19/2000

Labeling Error Prompts Recall of Isoniazid Used for Tuberculosis Susceptibility Testing

Kate Traynor

Becton, Dickinson and Company recently recalled a specific lot of the company's isoniazid because some vials may actually contain streptomycin. The Centers for Disease Control and Prevention (CDC) warns that antimicrobial susceptibility testing (AST) done with this batch of isoniazid is not reliable.

The isoniazid was sold individually (lot 9335260) and as part of Becton Dickinson's BACTEC S.I.R.E. susceptibility testing kits (lots 9327296, 9342298, and 9327298). According to CDC, the mislabeled product was sold from January through Aug. 25 of this year. CDC has advised laboratories to identify all tuberculosis isolates tested with these lots. 

Clinicians who care for tuberculosis patients should be informed of the recall and the potential need for repeat testing of isolates previously screened with the recalled isoniazid, noted CDC in its Sept. 1 Morbidity and Mortality Weekly Report. 

CDC recommended that tuberculosis isolates from patients not responding to treatment as expected should be retested immediately for isoniazid resistance. Repeat ASTs may also be advisable for isolates found resistant to first-line antituberculosis drugs and isolates from patients undergoing induction therapy. Last in line for potential retest are all other isolates for which isoniazid susceptibility results are unreliable. 

Clinical and laboratory tests to evaluate treatment failure are advised for patients who complete induction therapy yet still harbor isolates resistant to isoniazid only, said CDC. 

Maintenance therapy with isoniazid and rifampin was deemed acceptable by CDC for patients with good clinical results and no evidence of treatment failure. However, CDC warned that the two-drug regimen of isoniazid and rifampin, if taken by patients with unrecognized isoniazid resistance, could lead to treatment failure and might select for rifampin resistance. CDC recommended treating these patients with at least two additional drugs known to be effective against the tuberculosis isolates in question. 

Patients whose tuberculosis infections were cured using the standard six-month, four-drug treatment regimen do not need additional drug therapy, noted CDC.


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