Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Dissertation (Ph.D.)--University of Stellenbosch, 1996. / Bibliography. Also available via the Internet.

Prolonged therapy required to effectively treat mycobacterial infection frequently results in severe dose-limiting side-effects and drug resistance due to patient non-compliance with protracted dosage regimens. Biodegradable poly-a-hydroxy acid microspheres and microcapsules containing rifampicin (RIF) and isoniazid (INH) respectively have been prepared with the intention of providing high sustained site-specific concentrations to overcome some of the shortcomings of existing oral treatments. Due to the high dose, hydrophilicity and instability of both drugs, formulation strategies to attain high drug loading and methodologies to characterize in vitro drug release during ongoing decomposition were required. Stability indicating HPLC assays to quantify drug release have been developed, validated and applied to monitor drug release based on cumulative quantification of drug and degradates. A mathematical correction for serial decompositions associated with RIF was made based on the terminal pseudo equilibrium observed during stability studies. An isocratic HPLC assay was prospectively developed for the quantification of both drugs and their major metabolites in biological samples. Further preformulation studies confirmed the absence of significant polymorphs for both drugs when recrystallized from solvents later used in formulation development. Furthermore, thermal analysis revealed only modest interaction between the drugs and Resomer®. The high and moderate water solubilities of INH (145 mgmL-1) and RIF (1 mgmL-1) determined the selection of spray-drying (SD) and emulsion solvent evaporation (ESE) for RIF, whereas preparation of INH microcapsules relied solely on the former technique. Examination of the effects of varying RIF: polymer ratio, phase volumes and continuum presaturation with selected poly(L-lactide) and poly(D, L-lactide-co-glycolide) (PDLGA) Resomer® identified optimum conditions to maximize drug loading during a comparison of aqueous ESE with spray-drying with a range of nine further amorphous Resomer® polymers. Although yields were generally higher with ESE (85-90 %), SD (45- 75 %) was considered a superior preparation technique on the basis of the rapid production of microspheres of high and predictable drug loading (100 % of that attempted), with monodisperse granulometry and superior morphology. Release profiles were typically asymptotic characterized by a rapid `burst' of release followed by a slow release of residual entrapped RIF, irrespective of the preparative technique or polymer used. Poor yields (7.2 %) when SD low molecular weight (MW) PDLGA (8 kD) were greatly enhanced (74.8 %) by reduction in drying temperature and substitution of chloroform: dichloromethane (CFM: DCM) (1: 1) cosolvent with DCM. These conditions were adopted as the optimum parameters for further studies of blends of low (2 kD, R104) and moderate (11 kD, R202H) MW poly(D, L-lactide) (PDLLA); materials which demonstrated excellent sprayability and dramatically modulated the release of drug when combined compared to their use alone. Drug release showed a remarkable dependence on blend, dramatic acceleration being observed between 44 and 48 %w/w R104. Release over this range showed a marked dependence on medium temperature and led to the proposal of an autohydration mechanism linked to the hydrophilicity and glass transition (T9) of the blend which accounted for the sigmoidal profiles observed. First order dependence of release allowed calculation of Arrhenius derived activation energies of drug release in glassy anhydrous and rubbery plastic matrices of 630 and 320 J mol-1. Hydration and thermal studies supported the postulated diffusion mechanism, whereas granulometric and morphological examinations demonstrated that erosion did not contribute significantly. The criticality of matrix composition was further highlighted when interchange with nominally identical polymer, R202H, shifted the critical composition to 30 %w/w R104. Moreover, this observation contested the batch-to-batch reproducibility of commercial polymer. Substitution of DCM with halothane (HAL) and acetone (ACT) had a profound influence on the properties of compositionally identical ('R104: R202'H, 30: 70) microspheres, particularly release kinetics. This was attributed to the more rapid drying kinetics with the poor solvent, ACT, and the generation of a porous matrix. Consequently, drug was largely released during the 'burst' phase. Superior solvents, HAL and DCM resulted in enhanced matrix coherence at the expense of considerable residual solvent burdens (6 - 12.5 %), which allowed extensive matrix relaxation as solvent was lost with first order kinetics. This ageing process was followed by the development of an endotherm associated with the Tg as the matrix stabilized with a resultant increase in the induction period and a general retardation of drug release. Extension of the concept of blending R104 as release 'initiator' to a range of MW PDLGA of 50: 50 and 75: 25 comonomer ratio as release 'modulator' was of limited success generating release profiles reminiscent of each polymer when used alone. The magnitude of the 'burst' correlated to the precipitation kinetics of the predominant complementary PDLGA polymer as determined by cloud-point titration. Due to the more hydrophilic nature of the copolymers, at the critical concentration uncontrolled hydration resulted in a single rapid release phase. Spray-dried biodegradable INH microcapsules were prepared by a two stage process whereby SD cores of drug or in combination with biodegradable albumin or casein were subsequently coated with PDLGA by SD. The highly crystalline, aggregated and irregular morphology of SD drug resulted in poor coating efficiency and a rapid release of encapsulated drug. Protein microspheres of superior sphericity allowed more effective coating and hence slower INH release. It is concluded that SD has excellent industrial potential for the preparation of biodegradable poly-a-hydroxy acid microspheres for high dose drugs to be delivered directly to their site of action, e. g., intra-pulmonary. Indeed, the granulometry of these particles and, in particular, the hydrophilic character of blends of PDLLA described have considerable potential for the sustained delivery of drugs in the low volumes of fluid that prevails in the lung. These formulations might offset some of the limitations of current oral antimycobacterial therapy.

Thesis (Ph.D. in Pharmaceutical Sciences) -- University of Colorado at Denver and Health Sciences Center, 2005. / Typescript. Includes bibliographical references (leaves 86-92). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Nos Ãltimos anos, a melhoria dos mÃtodos de diagnÃstico micolÃgico e as doenÃas imunossupressoras causaram grande impacto na incidÃncia das micoses profundas e oportunistas em todo o mundo, fato que impulsionou a realizaÃÃo de estudos de prospecÃÃo por novas drogas antifÃngicas. A histoplasmose à uma micose sistÃmica, causada pelo fungo Histoplasma capsulatum var. capsulatum que, em pacientes hÃgidos, pode mimetizar a tuberculose quanto aos aspectos clÃnicos e radiolÃgicos. Alguns casos de histoplasmose refratÃria ao tratamento com drogas antifÃngicas convencionais vÃm sendo descritos. O objetivo deste trabalho foi determinar o efeito inibitÃrio, in vitro, das drogas antituberculose: isoniazida (INH), pirazinamida (PZA) e etambutol (EMB); antifÃngicas: anfotericina B (AMB), fluconazol (FLC), itraconazol (ITC) e voriconazol (VRZ) e de anÃlogos quÃmicos da isoniazida frente a cepas de H. capsulatum (n=30), assim como avaliar o emprego de diferentes meios de cultura para a realizaÃÃo dos testes de sensibilidade. Para isso, primeiramente, foram repicadas 18 cepas de H. capsulatum em Ãgar BHI e utilizadas na realizaÃÃo dos testes de sensibilidade frente aos agentes antituberculose citados e anÃlogos quÃmicos da isoniazida, isolados e em combinaÃÃo com os antifÃngicos FLC, ITC e VRZ por meio da tÃcnica de macrodiluiÃÃo em caldo. Cada uma das 12 cepas restantes foi repicada em Ãgar batata dextrose, Ãgar BHI, Ãgar malte a 2% e Ãgar lactrimel e, analisadas ao microscÃpio Ãptico quanto a presenÃa de macroconÃdios tuberculados, sendo quantificados de acordo com os parÃmetros: (0-10); (10-50); (>50) macroconÃdios/campo. As culturas foram empregadas na determinaÃÃo dos testes de sensibilidade frente aos agentes antifÃngicos AMB, FLC, ITC e VRZ, utilizando a tÃcnica de microdiluiÃÃo em caldo. As drogas antituberculose inibiram o crescimento das cepas in vitro com valores de CIM de 0,04 a 0,30 mg/mL para INH, 0,55 a 3,13 mg/mL para PZA e 1,56 a 6,25 mg/mL para EMB. No tocante Ãs drogas antifÃngicas, todas as cepas foram sensÃveis apresentando valores de CIM que variaram de 0,0625 a 0,25 Âg/mL para AMB; 15,62 a 62,5 Âg/mL para FLC; 0,0039 a 0,0312 Âg/mL para ITC e 0,00156 a 0,25 Âg/mL para VRZ. Quanto Ãs combinaÃÃes entre os fÃrmacos antituberculose e os derivados azÃlicos, todas foram capazes de inibir o crescimento in vitro das cepas de H. capsulatum, sendo detectado sinergismo nas nove combinaÃÃes. Os anÃlogos da isoniazida apresentaram valores de CIM 2, 4, 8 e 15 vezes superior a atividade da droga antituberculose padrÃo. A partir da anÃlise micromorfolÃgica do fungo repicados nos quatro meios de cultura foi identificado a menor quantificaÃÃo (0-10 macroconÃdios/campo) para Ãgar batata, Ãgar BHI, Ãgar malte e Ãgar lactrimel, perfazendo um total de 11, 10, 6 e 7 cepas, respectivamente. O meio de cultura Ãgar malte foi o mais adequado para produÃÃo de macroconÃdios (10-50) e (>50), norteando um total de 6 cepas, seguido do meio lactrimel, 5 cepas. Em relaÃÃo a determinaÃÃo da CIM e o meio de cultura utilizado para o procedimento, observou-se que quando o inÃculo era proveniente de cepas em Ãgar malte e Ãgar BHI foi possÃvel a visualizaÃÃo da CIM em 11 cepas. Enquanto repiques feitos em Ãgar batata e lactrimel nÃo foi possÃvel determinar os valores de CIM para 8 e 5 cepas, respectivamente. Os resultados deste estudo fornecem dados adicionais sobre o potencial antifÃngico das drogas antituberculose e suas interaÃÃes com os derivados azÃlicos. Entretanto, novos estudos se fazem necessÃrio, visando determinar os mecanismos de aÃÃo desses compostos no metabolismo celular dos fungos. / In the past years, the improvement of mycological diagnosis methods and immunosuppressive diseases have caused a great impact in the incidence of opportunistic and deep mycoses all around the world, which motivated the performance of new antifungal drugs prospective studies. Histoplasmosis is a systemic mycosis caused by the fungus Histoplasma capsulatum var. capsulatum, which may mimic tuberculosis, in healthy individuals, concerning clinical and radiological aspects.ome cases of histoplasmosis that are refractory to the treatment with conventional antifungal drugs have been described. The aim of this study was to determine the in vitro inhibitory effect of the antituberculosis drugs: isoniazid (INH), pyrazinamide (PZA) and ethambutol (EMB); antifungal drugs: amphotericin B (AMB), fluconazole (FLC), itraconazole (ITC) and voriconazole (VRZ) and chemical analogs of isoniazid against strains of H. capsulatum (n=30), as well as to evaluate the use of different culture media for the performance of the susceptibility tests. For such, first, the antituberculosis agents INH, PZA and EMB and the analogs of isoniazid were tested isolatedely, and then, in association with the antifungal drugs FLC, ITC and VRZ, against 18 strains of H. capsulatum, previously grown onto BHI agar, through broth macrodilution technique. Each of the 12 remaining strains grown onto potato agar, BHI agar, 2% malt extract agar and lactritmel agar were microscopically analyzed, concerning the presence of tuberculate macroconidia, which were quantified as follows: 0-10, 10-50 and >50 macroconidia/field. Fungal cultures were used to determine the susceptibility of H. capsulatum to the antifungal agents AMB, FLC, ITC and VRZ, through broth microdilution methodology. The antituberculosis drugs inhibited the in vitro growth of the fungal strains, with MICs ranging from 0.04 to 0.30 mg/mL for INH; 0.55 to 3.13 mg/mL for PZA and 1.56 to 6.25 mg/mL for EMB. Concerning antifungal drugs, all the strains were susceptible, with MIC values ranging from 0.0625 to 0.25 Âg/mL for AMB; 15.62 to 62.5 Âg/mL for FLC; 0.0039 to 0.0312 Âg/mL for ITC, and 0.00156 to 0.25 Âg/mL for VRZ. When associating antituberculosis drugs with azole derivatives, all associations inhibited the in vitro growth of H. capsulatum strains, and synergy was observed for the nine combinations tested. Analogs of isoniazide presented MICs of 2, 4, 8 and 15-fold better than the standard antituberculosis drug. Basing on micromorphological analysis, the lowest quantification of macroconidia/field (0-10) was observed for 11, 10, 6 and 7 strains previously grown onto potato agar, BHI agar, malt agar and lactritmel agar, respectively. Malt agar was the most adequate medium for the production of macroconidia, 10-50 and >50/field, with a total of six strains; followed by lactritmel agar, with 5 strains. Concerning the relationship between MIC and culture medium used during the test, it was observed that inoculum from strains grown onto malt agar and BHI agar allowed the detection of the MIC for 11 strains. On the other hand, for those inocula grown onto potato agar and lactritmel agar, the MIC values were not detected for 8 and 5 strains, respectively. The results of this study provide additional data on the antifungal potential of antituberculosis drugs and their interactions with azole derivatives. However, new studies are necessary in order to determine the mechanism of action of these compounds on fungal cellular metabolism.

Novos sistemas de liberação de fármacos têm sido desenvolvidos com o intuito de melhorar a eficácia terapêutica de muitos fármacos no tratamento de diferentes patologias. Os sistemas microparticulados têm despertado grande interesse devido a suas propriedades, suas vantagens sobre os sistemas de distribuição convencional e, conseqüentemente, melhoria na adesão ao tratamento. As micropartículas de quitosana são exploradas como sistemas de liberação sítio-específico, devido suas propriedades biodegradáveis, biocompatíveis e mucoadesivas. Assim, visando o tratamento da tuberculose, que atualmente é causa prevalente de morte considerando as doenças infecciosas no mundo, neste trabalho micropartículas constituídas de quitosana foram desenvolvidas para veicular isoniazida. A isoniazida, uma hidrazida do ácido isonicotínico, é uma dos fármacos mais poderosos entre os fármacos de primeira linha utilizados no tratamento da tuberculose devido à sua alta eficiência, baixa dose e de baixo custo, tornando-o um bom candidato para o desenvolvimento de uma formulação de liberação sítio-específica. Por spray-drying, as micropartículas inertes e com isoniazida obtidas apresentaram-se esféricas e com ampla distribuição de tamanho de partículas que variou entre 5 e 12 m, potencial zeta positivo e elevada eficiência de encapsulação. O perfil liberação in vitro em tampão fosfato salino (PBS) pH 7,4 apresentou formação de produto de degradação, sendo confirmado por espectrometria de massa como o ácido isonicotínico. Entretanto, a isoniazida mostrou ter uma liberação rápida (1 hora) a partir das micropartículas de quitosana em meio aquoso. Dessa forma, as micropartículas de quitosana desenvolvidas constituem um sistema promissor para veiculação da isoniazida e administração pulmonar e, finalmente, melhoria da terapia da tuberculose. Ademais, adequações do método deverão ser testadas considerando a via de administração pretendida, bem como será necessária a realização de estudos in vivo para avaliar o comportamento dos sistemas desenvolvidos em condições fisiológicas reais e a biodisponibilidade e biodistribuição do fármaco no organismo. / New drug delivery systems have been developed in order to improve the therapeutic efficacy of many drugs in the treatment of different pathologies. Microparticles have attracted great interest due to its properties, its advantages over conventional delivery systems and, consequently, better treatment adherence. The chitosan-based microparticles are exploited as delivery systems for site-specific, because their biodegradable, biocompatible and mucoadhesive properties. Thus, chitosan-based microspheres containing isoniazid were developed to target the treatment of tuberculosis, which is currently prevalent cause of death considering infectious diseases in the world. Isoniazid, an isonicotinic acid hydrazide, is one of the most powerful drugs among first-line drugs used to treat tuberculosis due to its high efficiency, low dose and low cost, making it a good candidate for the development of site-specific delivery system. By spray-drying, the isoniazid-loaded and free microparticles obtained presented wide size particle distribution with particle size ranging between 5 and 12 m, spherical morphology, positive zeta potential and high encapsulation efficiency. The in vitro release profile in phosphate buffered saline (PBS) pH 7.4 showed the formation of degradation product, which was confirmed by mass spectrometry as isonicotinic acid. However, isoniazid release from the microparticles was fast (1 hour) in water. Thus, the developed chitosan microparticles are a promising system as a vehicle to isoniazid and pulmonary administration, and ultimately to improve the therapy of tuberculosis. Moreover, adaptations of the method should be tested considering the intended route of administration and it will be necessary to perform in vivo studies to evaluate the behavior of the systems developed under physiological conditions and actual bioavailability and biodistribution of the drug in the body.

Tuberculosis (TB) is a highly contagious disease caused by the bacterium known as Mycobacterium tuberculosis which is widely spread in South Africa, especially in the rural areas of the Western Province. Rifampicin, isoniazid and pyrazinamide are the three most effective drugs against this organism. However, most of the current commercial anti-TB formulations are inconvenient to administrate. This results in patient non-compliance which has increased with incomplete tuberculosis treatment and further has intensified the mortality rate. The matter is especially severe amongst the paediatric and geriatric patients. Therefore, creating a "user-friendly" but non-alcoholic liquid formulation should improve the whole situation. The key to a successful formulation relies on sufficient concentrations of the drugs within the formulation together with acceptable stability of these drugs. Therefore, during the pre-formulation stage, the solubility and stability studies of rifampicin, isoniazid and pyrazinamide are to be conducted. Rifampicin, isoniazid and pyrazinamide were fully characterized and identified by means of spectroscopic and thermal techniques. A HPLC method for simultaneous analysis of the three drugs was developed and validated. This HPLC method was employed for all the solubility and stability assessments. Unbuffered HPLC water of pH value 7.01 was chosen as the aqueous solvent. This was decided after the stability of rifampicin, isoniazid and pyrazinamide was studied at a pH range of 2 to 10. The solubility and the stability studies of rifampicin, isoniazid, pyrazinamide, rifampicin with isoniazid, rifampicin with pyrazinamide, isoniazid with pyrazinamide and rifampicin combined with both isoniazid and pyrazinamide were performed in the presence of various agents. These agents can be categorized into three groups: the surfactants (poloxamer 188, poloxamer 407 and sorbitol) which could increase the intrinsic solubility or the drugs by altering the surface tensions of the aqueous solution medium, the suspending agents (carbopol 934 and carbopol 974P) which could enable the amount of dosage required to be homogeneously suspended in the formulation without considering the low intrinsic solubility factor of the drugs, and the complexing agents (ß-cyclodextrin, hydroxypropyl-ß-cyclodextrin and -cyclodextrin) which could initiated the inclusion complex between the host cyclodextrin and the drugs, thus further enhance the solubility of the drugs . The stability assessments were performed after 7-days stability trail with the HPLC method developed. Each drug/combination of drugs were stored in closed ampoules and subjected to 25, 40 and 60° C with or without nitrogen flushing while in the presence of the above mentioned agents. While assessing the solubility/stability of the drugs in the presence of the above mentioned surfactants, the phase-solubility curves indicate that both rifampicin and pyrazinamide fail to achieve the desired concentration. Moreover, the stability-time plots clearly indicate that these surfactants fail to enhance the general stabilities of the drugs. When the stabilizing effects of the above mentioned suspending agents were investigated, it was found that although the desired concentration could be easily accomplished by suspending the drug in the aqueous carbopol solutions, the stabilities of the different drug combinations were still below the regulatory level. Cyclodextrins are well known to form inclusion complexes with less polar drug molecules. The inclusion complexation could enhance both the solubility and the stability of the included drug molecules. The computer force field generated models of the cyclodextrin-drug were used to predict the complexation sites. The results indicated the all the inclusion complexation between the drugs and the cyclodextrins were favourable, but do not necessary protect the potential degradation sites of the drugs. The stability results confirmed the above findings as the cyclodextrins did not enhance the stability of the drugs. Various drug-drug interaction pathways were also predicted from the experimental observations which clearly indicated the stability reductions of these drugs in combination. This leads to the conclusion that a liquid formulation combining rifampicin, isoniazid and pyrazinamide should not initiate the use of aqueous solutions as the protic ions of the solution are able to initiate the degradation of these drugs.

Isoniazid (INH), one of the most effective agents in the treatment and prophylaxis of tuberculosis associated with a mild increase in liver transaminases in up to 20% of treated patients and severe hepatotoxicity in up to 2% of treated patients. Since the 1970's, a number of studies have been reported on the mechanism of INH-induced hepatotoxicity. The original studies in rats suggested that the hepatotoxic effect of INH was due to the microsomal metabolism of acetylhydrazine (AcHz, a metabolite of INH) to a reactive intermediate. More recently other workers have been unable to reproduce the original results in the rat, or other mechanistic models have been proposed. Therefore, it is necessary to establish a reproducible animal model which resembles INH hepatotoxicity in the human being. In these experiments,, male New Zealand white rabbits were used, and divided into 12 treatment groups of 6-8 rabbits each. Serum argininosuccinate lyase (ASAL) levels and histological changes in liver slides were chosen as indices of hepatotoxicity. After the determination of acetylator phenotype for each rabbit, INH and its metabolites, acetylisoniazid (AcINH), hydrazine (Hz) and AcHz were administered in a two-day regimen orally or subcutaneously. The results showed that the serum ASAL level in rabbits is a sensitive and specific enzyme marker which parallels the incidence of hepatic necrosis seen on histology. The serum ASAL control values 4.3±2.6 (SD) Takahara units were maintained until about 24 hrs after the first challenge of INH in the two-day regimen (0.36+3x0.26 mmol/kg/dx2d, s.c.); peak values of up to 2674 Takahara units occurred at about 72 hrs. No significant difference between the toxicity of INH given orally and subcutaneously was detected. Phenobarbital (PB) (0.1 mg/kgx3d, i.p.) pretreatment increased the elevation of serum ASAL level caused by INH (0.36+3x0.26 mmol/kg/dx2d, p.o.) significantly (p<0.05, F test) compared with the group without PB pretreatment. The 65 experimental rabbits were classified into populations of acetylator phenotype by measuring their acetylation rate of sulfamethazine (SMZ): fast acetylators with a SMZ t[formula omitted] of 12.8±4.4 (SD) (n=54) and slow acetylators with a SMZ t[formula omitted] of 50.3±10.4 (SD) (n=ll). Among the rabbits challenged with INH (0.36+3x0.26 mmol/kg/dx2d, p.o. or s.c.) with or without PB pretreatment, no correlation was found between the peak serum ASAL values and acetylation rate represented by SMZ t[formula omitted (r=0.05, n=18). This lack of this correlation was also present in rabbits challenged with AcINH and Hz. Among INH and its metabolites, AcINH, Hz and AcHz, Hz is the most potent hepatotoxin. Its effect is dose-dependent over the dose range (0.10+3x0.07, 0.14+3x0.10 and 0.19+3x0.14 mmol/kg/dx2d, p.o.). AcHz (0.36+3x0.26 mmol/kg/dx2d, s.c.), produced no significant hepatotoxic effect, which is contradictory to the results reported by other authors. AcINH (0.28+3x0.20 mmol/kg/dx2d, s.c, 0.42+3x0.30 mmol/kg/dx2d, s.c. or p.o.) had a intermediate hepatotoxic effect which is similar to that of INH. The results showed that (1) the rabbit is a reproducible animal model for studying INH hepatotoxicity; (2) the release of ASAL to serum and pathological changes resemble that seen in human beings; (3) the hepatotoxicity of INH is potentiated by PB pretreatment which is in accordance with the evidence in human beings of an increased risk in the presence of microsomal enzyme inducers; (4) the acetylation rate does not affect the hepatotoxicity of INH; (5) among the metabolites tested, Hz was most potent. These data indicate that the hypothesis that INH hepatotoxicity is due to microsomal metabolism of AcHz is probably incorrect. We think that it is more likely that Hz is responsible. Further studies are required to elucidate the exact mechanism in the rabbit model. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

Thesis (PhD (Medicine. Pharmacology))--University of Stellenbosch, 1996. / The work presented in this thesis has contributed to the clarification of a number of issues related to the clinical pharmacokinetics of isoniazid and hydrozine in juvenile and adult patients of both sexes subject to potentially deleterious environmental factors: acute tuberculous disease; nutritional deprivation; simultaneous ingestion of rifampicin, pyrazinamide and ethionamide, each of which is potentially toxic in its own right. The advances are embodied in the developments listed here below. ...

Philosophiae Doctor - PhD / Background: Tuberculosis (TB) is a major cause of morbidity and mortality among children (<15 years) in resource-limited countries. The World Health Organization (WHO) identified active contact screening and isoniazid preventive therapy (IPT) as essential actions for detecting and preventing childhood TB. Despite their benefits and inclusion in the policy of most National TB Programme (NTP) guidelines of the resource-limited countries, there is still a wide gap between policy and implementation. The implementation of contact screening for active case finding might be improved by the decentralised use of the Xpert MTB/RIF test in gastric lavage (GL) specimens, but this has not been previously assessed. Furthermore, although the provision of IPT to eligible child contacts has been a focus for implementation by the NTP of Rwanda since 2005, implementation has not previously been evaluated. The assessment of IPT uptake and adherence as well as associated factors could be informative for the programme. Therefore, we aimed to assess the diagnostic yield of Xpert MTB/RIF in GL among child contacts with suspected pulmonary tuberculosis (PTB) and the uptake of and adherence to IPT by eligible child contacts to make recommendations towards strengthening TB diagnostic and prevention in children in Kigali, Rwanda. Methods: The proposed study setting Kigali, the capital city of Rwanda, was the location for 30% of the national PTB case notifications in 2013-14.A conceptual framework based on ecological theory was used in this study. Quantitative, qualitative and mixed (using both quantitative and qualitative research methods in one study) research methods were applied, and various research designs were used depending on the research questions. The study involved a cross-sectional analysis of the diagnostic yield of Xpert MTB/RIF in GL among all child contacts with suspected TB. Across-sectional and prospective cohort study design was used to assess the uptake and adherence of IPT among eligible child contacts.