Using a single tablet daily to treat latent tuberculosis infection in Brazil: bioequivalence of two different isoniazid formulations (300 mg and 100 mg) demonstrated by a sensitive and rapid high-performance liquid chromatography-tandem mass spectrometry method in a randomised, crossover study

The recommended treatment for latent tuberculosis (TB) infection in adults is a daily dose of isoniazid (INH) 300 mg for six months. In Brazil, INH was formulated as 100 mg tablets. The treatment duration and the high pill burden compromised patient adherence to the treatment. The Brazilian National Programme for Tuberculosis requested a new 300 mg INH formulation. The aim of our study was to compare the bioavailability of the new INH 300 mg formulation and three 100 mg tablets of the reference formulation. We conducted a randomised, single dose, open label, two-phase crossover bioequivalence study in 28 healthy human volunteers. The 90% confidence interval for the INH maximum concentration of drug observed in plasma and area under the plasma concentration vs. time curve from time zero to the last measurable concentration “time t” was 89.61-115.92 and 94.82-119.44, respectively. The main limitation of our study was that neither adherence nor the safety profile of multiple doses was evaluated. To determine the level of INH in human plasma, we developed and validated a sensitive, simple and rapid high-performance liquid chromatography-tandem mass spectrometry method. Our results showed that the new formulation was bioequivalent to the 100 mg reference product. This finding supports the use of a single 300 mg tablet daily strategy to treat latent TB. This new formulation may increase patients’ adherence to the treatment and quality of life.

ELISA protocol for rapid screening of potential antitubercular drugs based on antigenic reactivity of mycobacterial ES-31 serine protease - a drug target supported by axenic culture of Mycobacterium tuberculosis H37 Ra strain in the presence of inhibitor.

Background: Mycobacterial ES-31 serine protease has been reported to be a drug target using protease and lipase inhibitors in axenic and macrophage cultures. Simple screening techniques are needed for rapid testing of anti-tubercular drugs. Aim: To demonstrate the usefulness of ELISA protocol based on antigenic reactivity of mycobacterial serine protease by indirect ELISA for detecting anti-tubercular activity. Material and Methods: Indirect ELISA for assessment of antigenic reactivity of mycobacterial ES-31 serine protease was standardized using ES-31Ag and anti-DSS-goat-serum and assessed the inhibition of the antigenic reactivity by isoniazid, an anti-tubercular drug and serine protease inhibitor and orlistat, a lipase inhibitor. Results: Optimal antigenic reactivity of mycobacterial ES-31 serine protease was observed at 5μg/well of ES-31 antigen and at 1:25 dilution of anti-DSS-goat-serum. Isoniazid showed 42% inhibition of ES-31 serine protease at 0.4μg/well, while orlistat showed inhibition of 60% at 0.5μg/well. Inhibition of Mtb H37Ra bacilli is further confirmed in axenic culture. 35% and 29% inhibition by isoniazid at 0.4μg/well and orlistat at 0.5μg/well were observed respectively on bacterial growth. Conclusion: Simple ELISA protocol based on assay of antigenic reactivity of mycobacterial ES-31 serine protease, a drug target, has been standardized for rapid screening of potential anti-tubercular drugs.

Effect of paracetamol on pharmacokinetics of isoniazid in Teddy goats

In this study the effect of paracetamol on pharmacokinetics [PK] of isoniazid [INH] in Teddy goats was investigated. INH was administered as a single oral dose at 10 mg/kg body weight to every experimental goat. After a wash out period of 7 days, INH and paracetamol [at the rate of 15 mg/kg body weight] were given simultaneously through oral route for investigation of drug interactions. Both times, following drug administration, blood samples were collected at predetermined time intervals from the jugular vein of each animal and analyzed for INH by spectrophotometric analysis. PK parameters were calculated using two compartment open model. When used with paracetamol, the value of biological half life [t1/2beta] of INH was significantly decreased [p<0.05] from 2.391 +/- 0.216 to 2.17 +/- 3.46 hours. The value for apparent volume of distribution [Vd] was also significantly decreased [p<0.05] from 0.905 +/- 0.327 to 0.786 +/- 0.161 L/kg and total body clearance [CL] was increased insignificantly [p>0.05] from 3.59 +/- 2.03 to 4.04 +/- 2.61 mL/min/kg. Based on these results, it was concluded that dose of isoniazid should be increased when concomitantly used with paracetamol

Drogas antituberculose: interações medicamentosas, efeitos adversos e utilização em situações especiais - parte 1: fármacos de primeira linha / Antituberculosis drugs: drug interactions, adverse effects, and use in special situations - part 1: first-line drugs

Os objetivos principais do tratamento da tuberculose são curar o paciente e minimizar a possibilidade de transmissão do bacilo para indivíduos saudáveis. Reações adversas ou interações das drogas antituberculose entre si e com outros fármacos podem causar modificação ou descontinuação da terapêutica. Revisamos sucintamente o novo tratamento farmacológico da tuberculose introduzido pelo Ministério da Saúde do Brasil em 2009 e mostramos os mecanismos gerais de ação, absorção, metabolização e excreção dos medicamentos utilizados no esquema básico. Descrevemos as reações adversas e as interações (com medicamentos, alimentos e antiácidos) assim como a abordagem mais adequada para situações especiais, como gravidez, amamentação, insuficiência hepática e renal. Também descrevemos os mecanismos pelos quais as interações das drogas antituberculose do esquema básico podem causar hepatite medicamentosa e as possíveis alternativas nessa situação.

The main objectives of tuberculosis therapy are to cure the patients and to minimize the possibility of transmission of the bacillus to healthy subjects. Adverse effects of antituberculosis drugs or drug interactions (among antituberculosis drugs or between antituberculosis drugs and other drugs) can make it necessary to modify or discontinue treatment. We briefly review the new guidelines for the pharmacological treatment of tuberculosis, introduced by the Brazilian National Ministry of Health in 2009, and describe the general mechanism of action, absorption, metabolization, and excretion of the first-line drugs used in the basic regimen. We describe adverse drug reactions and interactions (with other drugs, food, and antacids), as well as the most appropriate approach to special situations, such as pregnancy, breastfeeding, liver failure, and kidney failure. We also describe the mechanisms by which the interactions among the antituberculosis drugs used in the basic regimen can cause druginduced hepatitis, and we discuss the alternatives in this situation.

Drogas antituberculose: interações medicamentosas, efeitos adversos e utilização em situações especiais - parte 2: fármacos de segunda linha / Antituberculosis drugs: drug interactions, adverse effects, and use in special situations - part 2: second line drugs

Os objetivos principais do tratamento da tuberculose são curar o paciente e minimizar a possibilidade de transmissão do bacilo para indivíduos saudáveis. Reações adversas ou interações das drogas antituberculose entre si e com outros fármacos podem causar modificação ou descontinuação da terapêutica. Descrevemos os mecanismos gerais de ação, absorção, metabolização e excreção dos medicamentos utilizados no tratamento da tuberculose multidroga resistente (aminoglicosídeos, fluoroquinolonas, cicloserina/terizidona, etionamida, capreomicina e ácido para-aminossalicílico). Descrevemos as reações adversas e as interações (com medicamentos, alimentos e antiácidos) assim como a abordagem mais adequada para situações especiais, como gravidez, amamentação, insuficiência hepática e renal.

The main objectives of tuberculosis therapy are to cure the patients and to minimize the possibility of transmission of the bacillus to healthy subjects. Adverse effects of antituberculosis drugs or drug interactions (among antituberculosis drugs or between antituberculosis drugs and other drugs) can make it necessary to modify or discontinue treatment. We describe the general mechanism of action, absorption, metabolization, and excretion of the drugs used to treat multidrug resistant tuberculosis (aminoglycosides, fluoroquinolones, cycloserine/terizidone, ethionamide, capreomycin, and para-aminosalicylic acid). We describe adverse drug reactions and interactions (with other drugs, food, and antacids), as well as the most appropriate approach to special situations, such as pregnancy, breastfeeding, liver failure, and kidney failure.

Intestinal barrier function and serum concentrations of rifampin, isoniazid and pyrazinamide in patients with pulmonary tuberculosis

Intestinal barrier function and serum concentrations of rifampin, isoniazid and pyrazinamide were studied in healthy controls and patients with active pulmonary tuberculosis. A case-control study of 29 controls and 30 cases attending at the Health Center, July, 2004 to December, 2005 was conducted. The body mass index was significantly reduced in cases compared to controls (p < 0.001). The intestinal paracellular transport of lactulose was significantly (p = 0.019) reduced in cases compared to controls. The transcellular transport of mannitol and the lactulose:mannitol ratio were not significantly (p = 0.0698) reduced in cases compared to controls. Low serum concentrations of rifampin, isoniazid and pyrazinamide were observed in 81 percent (48/59), 92 percent (54/59) and 28 percent (12/59), respectively, in all individuals. The results demonstrated a marked decrease on intestinal paracellular transport in patients with active pulmonary tuberculosis and reduced serum concentrations of rifampin and isoniazid in both groups.

Pharmacokinetics of pyrazinamide in children with primary progressive disease of lungs.

BACKGROUND & OBJECTIVE: As the dosages recommended for children are based on weight, empirical and derived by extrapolation from the studies in adults, pyrazinamide (PZA) pharmacokinetics in children is likely to be different from adults. Limited information exists regarding the pharmacokinetics of PZA in paediatric patients of primary progressive disease (PPD) of lungs. This study aims to look at the changed pharmacokinetics of pyrazinamide in children with PPD of lungs by using reverse phase high-pressure liquid chromatography (HPLC). METHODS: A total of 40 children (age range 5 to 13 yr) of PPD were receiving pyrazinamide (30 mg/kg/day). On 11(th) day of short course antitubercular therapy, blood samples (two per day from 11(th) to 13(th) day) were collected at 0 h (pre-dose), 1, 2, 3, 4, 8 and 24 h after pyrazinamide administration and concentration of pyrazinamide was estimated by reverse phase high-pressure liquid chromatography. The mean peak serum concentration, the time to reach mean peak serum concentration, total clearance, concentration at time zero, volume of distribution, terminal elimination rate constant, elimination half-life, total area under serum concentration-time curve were measured. RESULTS: The mean serum concentrations of pyrazinamide were found higher than its minimum inhibitory concentration (20 microg/ml) required to inhibit the growth of tubercle bacilli from 1 to 8 h continuously. INTERPRETATION & CONCLUSION: Our results suggest that a dose of 30 mg/kg/day achieves much higher concentration of pyrazinamide as compared to its minimum inhibitory concentration (20 microg/ml). Therefore, lowering of pyrazinamide dosage is suggested in children for better patient compliance along with reduction in cost, side-effects and toxicity without compromising its efficacy.

Intestinal permeability and malabsorption of rifampin and isoniazid in active pulmonary tuberculosis

Low antimycobacterial drug concentrations have been observed in tuberculosis (TB) patients under treatment. The lactulose/mannitol urinary excretion test (L/M), normally used to measure intestinal permeability, may be useful to assess drug absorption. The objective of this research was to study intestinal absorptive function and bioavailability of rifampin and isoniazid in TB patients. A cross sectional study was done with 41 patients and 28 healthy controls, using the L/M test. The bioavailabilities of rifampin (R) and isoniazid (H) were evaluated in 18 patients receiving full doses. Urinary excretion of mannitol and lactulose, measured by HPLC, was significantly lower in TB patients. The serum concentrations of the drugs were below the expected range for R (8-24 mcg/mL) or H (3-6 mcg/mL) in 16/18 patients. Analyzing the drugs individually, 12/18 patients had low serum concentrations of R, 13/18 for H and 8/18 for both drugs. We suggest that there is a decrease in the functional absorptive area of the intestine in TB patients, which would explain the reduced serum concentrations of antituberculosis drugs. There is a need for new approaches to improve drug bioavailability in TB patients.

Standardization of the method for estimation of ethambutol in pharmaceutical preparations and biological fluid.

A simple column chromatographic method for determination of ethambutol (EMB) in pharmaceutical preparations containing EMB in combination with other anti-TB drugs is presented. The method involved extraction of EMB into an organic solvent, followed by basification and column chromatographic separation on Amberlite CG 50 (100-200 mesh) and elution with suitable eluants and estimation at a wavelength of 270 nm. The assay was linear from 25 to 400 microg/ml. The relative standard deviations of intra and inter day assays were lower than 5%. Ethambutol was recovered from human urine quantitatively and stable for a period of at least one week in urine stored at -20 degrees C.

Clinical relevance of reduced bioavailability of rifampicin.

Bioavailability (BA) of rifampicin (RMP) is a critical factor in successful treatment of tuberculosis. The BA of RMP can be reduced by pharmaceutical factors, patient factors and drug interactions. Failure of treatment and development of drug resistance are potential consequences of reduction in BA and it is necessary to understand and control the factors influencing BA of RMP.

Resistencia a fármacos antibacilares en tubeculosis y microbacteriosis en enfermos VIH+/SIDA / Resistance to antibacillary drugs in tuberculosis and mycobacteriosis in HIV+/AIDS patients

Desde 1989 hasta Julio de 1994 el Laboratorio de Referencia Nacional de Micobacterias procesó cepas de 99 pacientes VIH/SIDA con enfermedades por micobacterias. En 87 se efectuaron las pruebas de tipificación; 73 (83.9 porciento) resultaron M. tuberculosis y 14 (16.1 porciento) M. no tuberculosis, 12 de ellas del complejo MAI. El test de sensibilidad a drogas antituberculosas se realizó en 81 casos, 69 del complejo M. tuberculosis y en los 12 MAI; estos últimos fueron todos resistentes, la mayoría a 5 de las 8 drogas probadas. De los 69 casos de TBC, 42 eran nuevos, vírgenes a tratamiento y en ellos se encontró un 11.9 porciento de resistencia inicial global. Este porcentaje es semejante a las cifras históricas nacionales, determinadas en enfermos VIH (-). Se concluye que la resistencia en estos pacientes no guarda relación con su condición biológica de VIH+/SIDA, sino con su pobre adherencia al tratamiento, por sus condiciones socioculturales

Interaçäo medicamentosa em pneumologia / Drug interactions in pneumology

Como conseqüência do uso freqüente de medicaçäo simultânea podem advir tanto complicaçöes leves quanto reaçöes colaterais sérias e até fatais. A farmacologia tem progredido no sentido de permitir um melhor conhecimento da interaçäo das drogas, prevenindo a maioria destes efeitos adversos. Entretanto, a prevençäo é limitada, tendo em vista a discrepância entre o número de interaçöes publicadas e o número de possíveis combinaçöes de medicamentos em doentes