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Int J Tuberc Lung Dis. 1999 Nov;3(11 Suppl 3):S325-8; discussion S351-2.

Determination of rifampicin, isoniazid and pyrazinamide by high performance liquid chromatography after their simultaneous extraction from plasma.

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Department of Pharmacology, University of Cape Town Medical School, Observatory, Western Cape, South Africa.



Isoniazid (INH), rifampicin (RIF), and pyrazinamide (PZA) are first-line antituberculosis drugs. Due to difficulties in producing effective combined formulations of these three drugs, the bioavailability of new combination formulations needs to be assessed prior to registration.


To develop a rapid, simple and sensitive high performance liquid chromatography (HPLC) assay method suitable for assaying RIF, INH and PZA in large numbers of plasma samples generated in bioavailability studies.


RIF, desacetyl-rifampicin (DRIF), INH and PZA were extracted simultaneously from plasma using a solid phase extraction column. RIF and DRIF were quantitated by HPLC using an 80% acetonitrile/0.1% trifluoroacetic acid (TFA) mobile phase and a C8 reversed phase column. INH and PZA were also quantitated on a C8 reversed phase column, but a 3% acetonitrile/0.6% TFA mobile phase was used.


Mean recovery of RIF, DRIF and PZA from plasma was well over 90%, and over 70% for INH. Calibration graphs were linear for all the drugs in their therapeutic range. Correlation coefficients were all above 0.9995, and between- and within-run coefficients of variation below 10%.


A simple, accurate, sensitive and cost effective assay for first-line antituberculosis drugs has been developed.

[Indexed for MEDLINE]

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