Rapid liquid chromatographic method for the estimation of isoniazid and pyrazinamide in plasma and urine

Ion interaction reagent reversed-phase high-performance liquid chromatography determination of anti-tuberculosis drugs and metabolites in biological fluids

New methods of ion interaction reagent (IIR) RP-HPLC are presented for the determination of anti-tuberculosis drugs and their metabolites, singly or in multi-component mixtures, in biological fluids. The following analytes are considered: isoniazid, ethionamide, pyrazinamide, morphazinamide, p-aminosalicylic acid, nicotinic and isonicotinic acids. Aqueous solutions of three different ion interaction reagents are alternatively or comparatively used as the mobile phases, namely: (A) 5.00 mM octylamine at pH 3.00 for o-phosphoric acid, (B) 5.00 mM octylamine at pH 8.00 for o-phosphoric acid, and (C) 5.00 mM 1,6 diaminohexane at pH 6.00 for o-phosphoric acid. The response linearity between peak area and analyte concentration is verified for all the analytes in the concentration range within the determination limits and 2.00 mg/l. Detection limits are always lower than 82 microg/l for standard solutions; in the analysis of samples of rat serum, rat plasma and human serum, the matrix effect is negligible, the detection limits are always lower than 94 microg/l and the average recovery yield is always greater than 96%.

Low serum antimycobacterial drug levels in non-HIV-infected tuberculosis patients

BACKGROUND

Despite the use of directly observed therapy (DOT) by tuberculosis control programs, patient treatment failure, relapse, and acquired drug resistance remain problematic in a small number. We investigated serum drug levels in non-HIV-infected tuberculosis patients who were receiving DOT by the health department and did not respond to treatment as expected.

METHODS

The indications for checking levels were as follows: (1) slow clinical response or failure to convert the sputum culture within 12 weeks; (2) treatment failure, early disease relapse < 13 months since being declared cured; (3) relapse, late disease reactivation > or = 13 months since being declared cured; and (4) acquired drug resistance while receiving DOT. Baseline characteristics of control subjects who responded to therapy as expected were compared. Venous blood for analysis was obtained at 2 h after directly observed ingestion and measured by high-performance liquid chromatography.

RESULTS

Twenty-four patients receiving daily or twice-weekly standard therapy with isoniazid (INH, 300 or 900 mg) and rifampin (RMP, 600 mg) were identified; 22 had drug levels evaluated at 2 h. For INH, 15 of 22 patients (68%) had levels less than the reported target range. For RMP, 14 of 22 patients (64%) had low levels. Among the 14 patients receiving INH, 900 mg, and RMP, 600 mg, 4 (29%) had very low levels of both. Use of a combination INH/RMP tablet was associated with lower INH levels (p=0.04); however, RMP levels were higher (p<0.02). Alcohol use was associated with significantly higher RMP (p<0.01) serum concentrations.

CONCLUSIONS

Important questions remain concerning the utility and timing of serum drug measurements. However, if a patient is not responding to therapy as expected and one is assured that the Mycobacterium tuberculosis organism is susceptible to the drugs given and that the patient is taking the medication as prescribed, drug level monitoring should be considered.

Rapid, specific and sensitive method for isoniazid determination in serum

An original simple, specific and rapid high-performance liquid chromatographic assay for the determination of isoniazid (INH) in human serum is presented. The drug was extracted from the serum by protein precipitation with 30% (w/v) trichloroacetic acid, then the drug was reacted with the coupling reagent, trans-cinnamaldehyde, to form a derivative absorbing at 340 nm. A 20-microliters aliquot was injected into the chromatograph after neutralization with 1 M KOH solution. A liquid chromatograph equipped with a reversed-phase 30-microns C18 precolumn linked to a 4-microns C18 analytical column was used. The drug was eluted with a mixture of acetonitrile-water-triethylamine-acetic acid (400:600:2:1, v/v), pH value was 5 +/- 1. Flow-rate and wavelength were set at 1 ml/min and 340 nm, respectively. The extraction recoveries from human serum averaged 100% for INH at concentrations of 1, 2 and 4 mg/l. The coefficients of variation for three different concentrations for INH in serum in the within-day study varied between 1.2 and 3.5%, whereas those in the day-to-day study varied between 2.8 and 4.3%.

Comprehensive assay for pyrazinamide, rifampicin and isoniazid with its hydrazine metabolites in human plasma by column liquid chromatography

A comprehensive assay for determination of pyrazinamide (PZA), rifampicin (RIF), isoniazid (INH) and hydrazine metabolites is described. The method involves organic solvent extraction of PZA and RIF, followed by derivatization of INH, monoacetylhydrazine (mHYD) and hydrazine (HYD) with salicylaldehyde and extraction with diethyl ether. Acetylisoniazid (acINH) and diacetylhydrazine (dHYD) were hydrolyzed to INH and mHYD, respectively, and processed as above. Using a gradient solvent programmer, PZA and RIF were analyzed on a C8 (5 microns) column at 248 nm, while INH and metabolites were analyzed on a C18 (5 microns) ODS2 column at 280 nm.

High-performance liquid chromatography with UV detection and diode-array UV confirmation of isonicotinic acid hydrazide in cattle milk

A method for the determination of isonicotinic acid hydrazide (isoniazid) in milk was developed. Milk was deproteinized with trichloroacetic acid. Isoniazid was condensed with cinnamaldehyde and assayed on a reversed-phase HPLC system, with good sensitivity and accuracy (10 micrograms/l) with UV detection at 330 nm. Use of solid-phase extraction with a C18 cartridge allows the detection limit to be lowered to 0.1 microgram/l with UV detection and confirmation of isoniazid hydrazone from the diode-array UV spectrum.