Theses (Msc.(Med.)(Pharmacy))--University of Limpopo, 2010. / With the availability of Highly Active Antiretroviral Therapy (HAART), one of the limitations of treatment safety is the occurrence of adverse events associated with antiretroviral agents. The aim of this study was to establish whether stavudine dosage reduction prevents toxicity from developing and minimizes the incidence of symptomatic hyperlactataemia/lactic acidosis (LA) in adults female HIV/AIDS infected patients. This retrospective study covered adult patients treated at the adult ARV clinic, Dr George Mukhari Hospital. The records of 88 patients aged between 27 and 59 years, initiated and treated from August 2004 to January 2006, were analyzed ( 67 females and 21 males). Twenty nine females started their treatment on a regimen containing 40 mg stavudine while 38 females were started on 30 mg stavudine. A group of male patients (n=21) were included for comparison. Seven males started on 40 mg stavudine and 14 were on 30 mg stavudine. Ten out of twenty nine females who started treatment on 40 mg stavudine developed elevated lactate levels while nineteen received 30 mg stavudine as reduced dose. Eight out of nineteen further developed elevated lactate levels when on 30 mg stavudine but eleven out of nineteen remained stable on treatment with 30 mg stavudine as reduced dose. In the group started on 30 mg stavudine, thirteen females out of thirty seven developed elevated lactate levels while twenty four were stable on their treatment. Key words: stavudine, dosage reduction, lactate levels, hyperlactataemia, lactic acidosis.

The success of scale up of antiretroviral therapy (ART) in low- and middle-income countries (LMICs) is in large part due to the introduction of a “public health approach” to access advocated by the World Health Organization (WHO) which emphasized standardized treatment regimens that could be purchased in large quantities and delivered at scale. In 2010 the WHO updated their global HIV treatment guidelines recommending the substitution of stavudine with tenofovir (both of which are members of the non-nucleoside reverse transcriptase inhibitor (NRTI) class of drugs) in first-line antiretroviral therapy (ART). Given the size of treatment programs in sub-Saharan Africa, changing the NRTI used in first-line therapy for HIV could have a substantial impact on treatment outcomes. We conducted three prospective cohort studies using clinical datasets from several sub-Saharan African countries to answer questions surrounding the impacts of exposure to tenofovir in first-line therapy. The first study examines the frequency of stavudine use and single-drug substitutions (substituting the NRTI in first-line ART) in three regions in sub-Saharan Africa by calendar year, 2004–2014. We found a total of 33,441 (8.9%; 95% CI: 8.7–8.9%) single-drug substitutions occurred among 377,656 patients in the first 24 months on ART, close to 40% of which were amongst patients on stavudine. The decrease in single-drug substitutions corresponded with the phasing out of stavudine. We saw an 80% reduction in the risk of single-drug substitutions when comparing tenofovir to stavudine and close to a 70% reduction in the risk when comparing zidovudine to stavudine. The second study uses a regression discontinuity design to evaluate the impact of national HIV treatment guideline changes in South Africa and Zambia recommending tenofovir in first-line ART on treatment outcomes. We found that updated WHO guidelines increased the proportion of patients initiating tenofovir (risk difference (RD) (South Africa): 81%; 95% CI: 73%, 89%; RD (Zambia): 42%; 95% CI: 38%, 45%). Intent to treat estimates showed a decrease in single-drug substitutions in South Africa (RD: -15%; 95% CI: -18%, -12%) and Zambia (RD: -2.0%; 95% CI: -3.6%, -0.3%). In both countries, there was no effect on mortality, attrition or viral load failure (South Africa only). The third study investigates the effect of the 2012 tenofovir stock shortage in South Africa on provider and patient level outcomes, using data from four public-sector Right to Care clinics, two of which experienced a tenofovir stock shortage and two that did not. While imprecise, our results suggest a potential shift in how providers managed patients during the period of the shortage, mainly, a noticeable decrease in the average number of days between visits during the shortage compare to before or after at all four clinics and a significant difference in the proportion of patients missing visits. Difference-in-difference regression results showed a small, but significant, increase in the risk of missed visits during the shortage compared to after (RD: 1.2%; 95% CI: 0.5%, 2.0%), mainly driven by ACTs clinic. No significant difference was seen in other outcomes. Great strides have been made to extend access to ART as well as increase the quality of the services provided to patients in sub-Saharan Africa. Continued access to and a consistent supply of tenofovir in this setting is necessary for patients to receive drugs that are comparable to those used for HIV treatment in high-income countries, as we show that phasing out of stavudine and for either zidovudine or tenofovir potentially reduced toxicities and potentially improved quality of life in multiple regions throughout sub-Saharan Africa. While we show little effect on treatment outcomes when comparing patients accessing care and treatment during the shortage of tenofovir compared to those that did not, this most likely reflects the clinics’ ability to offset the crisis by continuing to initiate newly diagnosed and eligible patients on treatment and keep treatment experienced patients on their current regimen.

HIV/AIDS is the most threatening and challenging infectious diseases of our time, with the highest increase of newly infected cases reported. This infectious disease was discovered in the early eighties under homosexual men and was later to be discovered in heterosexuals. HIV is a systemic immunosuppressive disorder which causes a depletion of CD4+ T cells and develops into the acquired immunodeficiency syndrome - AIDS. Africa is the continent most affected by HIV/AIDS with the southern parts of Africa having the highest prevalence rates compared to the rest of Africa. Statistics indicate that AIDS is responsible for 3% of deaths in children worldwide - one in seven people dying of an HIV-related illness is a child under the age of 15 years. It was stated by the WHO that countries should develop improved antiretrovirals regimes for the prevention of mother-to-child transmission. Difficulties in administering antiretrovirals (ARVs) to patients (especially children) are the strict dosage regimes and the severe adverse reactions. These factors complicate patient adherence. The list of problems in treating patients is endless and includes the distribution, stability as well as the low efficacy of these drugs. Most of the above mentioned problems and obstacles related to ARVs and ARV treatment could be minimized or eliminated by the use of a stable and effective drug delivery system. Enhancing ARV treatment may be accomplished by the use of the Pheroid™ drug delivery system. Pheroids™ consists mainly of fatty acids and sterile nitrous oxide gassed water. Pharmacological active substances are entrapped into submicron and micron sized structures called Pheroids™. Research showed promising results and advantages in delivering drugs through oral and transdermal routes using Pheroid™ technology. The focus of this study was to test the possible enhancement of the efficacy of antiretrovirals using Pheroid™ technology. The assays used to study this possible enhancement were a modified neutral red and a modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. These assays confirmed and illustrated the toxic and protective properties of the tested ARVs (stavudine, lamivudine and nevirapine). An MT-2 cell line was used and infected with an HIV-1 strain, SW7-TCL. Applying Pheroid™ technology in these assays resulted in massive cell death, due to increased ARV toxic levels within the cells. Viability tests proved that Pheroids™ had no effect on the viability of cells at the concentration typically used. This confirmed the enhancing properties of Pheroids™ in the delivery of drugs into the cells. The MTT assay was further adapted from a seven day incubation period to a three day incubation period. By using a low concentration series and a three day incubation period the loss of cells through toxicity was partially overcome. One of the problems that arose form this study was the non-reproducibility of the results. Absorbance levels fluctuated at specific concentrations of the same ARV, which cause difficulties in comparing results. This result was repeatedly confirmed in this syncytium forming infection model. In conclusion, Pheroid™ technology enhanced the delivery of ARVs into the cells although it resulted in cell death. Both the neutral red and MTT assays were found to be inaccurate but further development, research and assay optimization could result in improved in vitro studies. The article format was used for this thesis, as described in the general academic rules in section A.13.7.3 of the North West University. Chapter 1 deals with HIV/AIDS related problems, statistics and treatment obstacles. Chapter 2 is a summary of the cell viability assays used in this study. Pheroid™ technology and its application to ARV treatment are dealt with in chapter 3. The proposed article for submission in the journal Cell Death and Differentiation has been included in chapter 4. Some of the results from the study are reported in the article and annexures, whilst other results are shown and discussed in Chapter 5. Chapter 6 gives a conclusion and final summary of this study. All other experimental methods and results are enclosed in the annexures, as is the "Guide for authors" for the article. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

Introduction: Stavudine is a commonly used drug in paediatric antiretroviral treatment (ART) regimens. Due to toxicity concerns, however, the drug abacavir has replaced stavudine in first-line paediatric regimens inmany countries.Wedescribe the frequency of stavudine toxicity in children receiving ART at a treatment clinic in Soweto, South Africa. Methods: Data on patient characteristics and outcomes of ART were collected from a cohort of 2222 HIV-infected children initiating ART between 2004 and 2008 when stavudine-containing regimenswere routinely recommended. At several time-points after treatment initiation, we estimate the proportion of children where an attending clinician discontinued stavudine due to lipodystrophy, pancreatitis, lactic acidosis or peripheral neuropathy. Factors associated with stavudine-related toxicities were identified. Results: At ART initiation, most children had advanced disease. The majority initiated an efavirenz/lamivudine/stavudine regimen (n¼1422), and 76% of children remained on their initial ART regimen after a median 19.9 months of ART. Replacement of stavudine due to drug toxicity occurred at a rate of 28.8 per 1000 child years on treatment (95% confidence interval¼23.6–35.2). Rates of toxicity increased with treatment duration (in their first year of ART stavudine was replaced in 0.5% of children, but after 3 years stavudine had been changed to abacavir in 12.6% of children). Toxicity was more common in older children and in girls. Lipodystrophy accounted for 87 of 96 toxic events. Conclusion: Stavudine-associated toxicity resulting in single-drug substitution was uncommon in this cohort, though its frequency increased steadily with ART duration, especially with lipodystrophy. Where drug options are limited, stavudine remains a relatively well tolerated and effective option for children.

A síndrome da imunodeficiência adquirida é causada pelo vírus da imunodeficiência humana e é caracterizada por provocar depleção física e funcional do sistema imune do organismo, através da infecção citopática de células CD4+. Muitos fármacos anti-retrovirais tem sido desenvolvidos e estão disponíveis comercialmente. Para atuar no controle de qualidade de medicamentos deve-se continuamente estudar o desenvolvimento e a validação de novas metodologias para quantificação de fármacos, para serem aplicadas nos estudos de estabilidade de formulações farmacêuticas e na análise de produtos de degradação. Neste trabalho foram utilizadas duas técnicas analíticas, a espectrofotometria direta no UV/VIS e a cromatografia líquida de alta eficiência (CLAE), para a determinação quantitativa de zidovudina (AZT) e estavudina (d4T).em medicamentos. Ambos os métodos foram validados com relação à linearidade, exatidão, precisão, especificidade e limite de detecção e quantificação. O método validado para a CLAE foi também empregado para a determinação quantitativa da timina, produto de degradação do AZT e da d4T. A metodologia validada por CLAE foi utilizada na realização de estudos de estabilidade acelerada dos anti-retrovirais contidos nas diferentes preparações farmacêuticas. Realizou-se o estudo da estabilidade em três diferentes condições: temperatura ambiente, 40 oC / 75% UR e 50 oC / 90% UR. Tanto a zidovudina (Fabricante A) e estavudina (Fabricante B) apresentaram decaimento cinético de zero ordem com prazos de validade a 50 oC / 90% UR de 10, 3 e 2 meses, respectivamente. / The acquired immunodeficiency syndrome is characterized by causing physical and functional depletion of the organism’s immune system, through the cytophatic infection of CD4+ cells. Several antiretroviral drugs has been developed and commercially made available. In order to assure the quality control of drugs it is necessary to develop and validate new analytical methodologies to perform the quantitative determination of drugs and stability studies of pharmaceutical formulations by determining the drug itself and its degradation products. In this research two analytical techniques, direct UV/VIS spectrophotometry and high performance liquid chromatography (HPLC), were used for the quantitative determination of zidovudine (AZT) and stavudine (d4T) in pharmaceutical preparations. Both methods were validated and parameters like linearity, precision, accuracy, specificity, limit of detection and limit of quantification, were determined. The validated HPLC method was also applied for quantitative determination of timine, a degradation product of AZT and d4T. The validated HPLC method was applied to accelerate stability studies of AZT and d4T in different pharmaceutical preparations. The stability studies were performed at three different conditions: room temperature, 40 oC / 75% RH and 50 oC / 90% RH. Both AZT and d4T (Industry A) and d4T (Industry B) pharmaceutical preparations presented a zero order degradation reaction. The three formulations presented a shelf-life of 10, 3 and 2 months, respectively, at 50 oC / 90% RH.

A síndrome da imunodeficiência adquirida é causada pelo vírus da imunodeficiência humana e é caracterizada por provocar depleção física e funcional do sistema imune do organismo, através da infecção citopática de células CD4+. Muitos fármacos anti-retrovirais tem sido desenvolvidos e estão disponíveis comercialmente. Para atuar no controle de qualidade de medicamentos deve-se continuamente estudar o desenvolvimento e a validação de novas metodologias para quantificação de fármacos, para serem aplicadas nos estudos de estabilidade de formulações farmacêuticas e na análise de produtos de degradação. Neste trabalho foram utilizadas duas técnicas analíticas, a espectrofotometria direta no UV/VIS e a cromatografia líquida de alta eficiência (CLAE), para a determinação quantitativa de zidovudina (AZT) e estavudina (d4T).em medicamentos. Ambos os métodos foram validados com relação à linearidade, exatidão, precisão, especificidade e limite de detecção e quantificação. O método validado para a CLAE foi também empregado para a determinação quantitativa da timina, produto de degradação do AZT e da d4T. A metodologia validada por CLAE foi utilizada na realização de estudos de estabilidade acelerada dos anti-retrovirais contidos nas diferentes preparações farmacêuticas. Realizou-se o estudo da estabilidade em três diferentes condições: temperatura ambiente, 40 oC / 75% UR e 50 oC / 90% UR. Tanto a zidovudina (Fabricante A) e estavudina (Fabricante B) apresentaram decaimento cinético de zero ordem com prazos de validade a 50 oC / 90% UR de 10, 3 e 2 meses, respectivamente. / The acquired immunodeficiency syndrome is characterized by causing physical and functional depletion of the organism’s immune system, through the cytophatic infection of CD4+ cells. Several antiretroviral drugs has been developed and commercially made available. In order to assure the quality control of drugs it is necessary to develop and validate new analytical methodologies to perform the quantitative determination of drugs and stability studies of pharmaceutical formulations by determining the drug itself and its degradation products. In this research two analytical techniques, direct UV/VIS spectrophotometry and high performance liquid chromatography (HPLC), were used for the quantitative determination of zidovudine (AZT) and stavudine (d4T) in pharmaceutical preparations. Both methods were validated and parameters like linearity, precision, accuracy, specificity, limit of detection and limit of quantification, were determined. The validated HPLC method was also applied for quantitative determination of timine, a degradation product of AZT and d4T. The validated HPLC method was applied to accelerate stability studies of AZT and d4T in different pharmaceutical preparations. The stability studies were performed at three different conditions: room temperature, 40 oC / 75% RH and 50 oC / 90% RH. Both AZT and d4T (Industry A) and d4T (Industry B) pharmaceutical preparations presented a zero order degradation reaction. The three formulations presented a shelf-life of 10, 3 and 2 months, respectively, at 50 oC / 90% RH.

HIV/AIDS is the most threatening and challenging infectious diseases of our time, with the highest increase of newly infected cases reported. This infectious disease was discovered in the early eighties under homosexual men and was later to be discovered in heterosexuals. HIV is a systemic immunosuppressive disorder which causes a depletion of CD4+ T cells and develops into the acquired immunodeficiency syndrome - AIDS. Africa is the continent most affected by HIV/AIDS with the southern parts of Africa having the highest prevalence rates compared to the rest of Africa. Statistics indicate that AIDS is responsible for 3% of deaths in children worldwide - one in seven people dying of an HIV-related illness is a child under the age of 15 years. It was stated by the WHO that countries should develop improved antiretrovirals regimes for the prevention of mother-to-child transmission. Difficulties in administering antiretrovirals (ARVs) to patients (especially children) are the strict dosage regimes and the severe adverse reactions. These factors complicate patient adherence. The list of problems in treating patients is endless and includes the distribution, stability as well as the low efficacy of these drugs. Most of the above mentioned problems and obstacles related to ARVs and ARV treatment could be minimized or eliminated by the use of a stable and effective drug delivery system. Enhancing ARV treatment may be accomplished by the use of the Pheroid™ drug delivery system. Pheroids™ consists mainly of fatty acids and sterile nitrous oxide gassed water. Pharmacological active substances are entrapped into submicron and micron sized structures called Pheroids™. Research showed promising results and advantages in delivering drugs through oral and transdermal routes using Pheroid™ technology. The focus of this study was to test the possible enhancement of the efficacy of antiretrovirals using Pheroid™ technology. The assays used to study this possible enhancement were a modified neutral red and a modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. These assays confirmed and illustrated the toxic and protective properties of the tested ARVs (stavudine, lamivudine and nevirapine). An MT-2 cell line was used and infected with an HIV-1 strain, SW7-TCL. Applying Pheroid™ technology in these assays resulted in massive cell death, due to increased ARV toxic levels within the cells. Viability tests proved that Pheroids™ had no effect on the viability of cells at the concentration typically used. This confirmed the enhancing properties of Pheroids™ in the delivery of drugs into the cells. The MTT assay was further adapted from a seven day incubation period to a three day incubation period. By using a low concentration series and a three day incubation period the loss of cells through toxicity was partially overcome. One of the problems that arose form this study was the non-reproducibility of the results. Absorbance levels fluctuated at specific concentrations of the same ARV, which cause difficulties in comparing results. This result was repeatedly confirmed in this syncytium forming infection model. In conclusion, Pheroid™ technology enhanced the delivery of ARVs into the cells although it resulted in cell death. Both the neutral red and MTT assays were found to be inaccurate but further development, research and assay optimization could result in improved in vitro studies. The article format was used for this thesis, as described in the general academic rules in section A.13.7.3 of the North West University. Chapter 1 deals with HIV/AIDS related problems, statistics and treatment obstacles. Chapter 2 is a summary of the cell viability assays used in this study. Pheroid™ technology and its application to ARV treatment are dealt with in chapter 3. The proposed article for submission in the journal Cell Death and Differentiation has been included in chapter 4. Some of the results from the study are reported in the article and annexures, whilst other results are shown and discussed in Chapter 5. Chapter 6 gives a conclusion and final summary of this study. All other experimental methods and results are enclosed in the annexures, as is the "Guide for authors" for the article. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

Objective: The objective of this retrospective cohort study is to assess whether demographic and anthropometric parameters, laboratory tests, co-morbidity, co-infection, treatment regimen, IRIS and adherence predict response to HAART as measured by CD4 count, weight gain and functional status in a cohort of patients in Roma, the Kingdom of Lesotho. Method: Data were collected from a computerised database of the Antiretroviral Centre of the hospital. A cohort of 300 subjects was identified from hospital records from January 2007. Each of these subjects was followed up over a period of 12 months with data obtained for at least two visits within the 12-month span. Data were obtained on weight and CD4 at baseline, three months and also at six and 12 months, and data for haemoglobin were obtained only at 12 months. Variables that may be potential confounders were identified and univariate and multivariate logistic regression analyses were carried out to establish differences independent of confounding factors for the combined endpoints, as well as for each endpoint separately. Results: Three-hundred patient records were analysed. Approximately 70% of the patients had a CD4 increase of at least 150 cells over baseline values at the end of the review period and in 52.3% of the patients an increase in weight of 10% over baseline measurements was seen. Seventy-nine patients (26.3%) had a haemoglobin level of at least 14g/dL at 12 months, regardless of baseline values or gender. The inclusion of Zidovudine (AZT) in treatment regimens was found in 73% of the patients and in multivariate analysis AZT was associated with not having anaemia at the end of the review period. However there was a slight reduction in haemoglobin level in the first two to three months of therapy in comparison with both Stavudine (d4T) and Tenofovir (TDF) but not significant enough to result in clinical anaemia. Baseline CD4 values were similar for all treatments options but dissimilar in other outcome variables and continued to vary significantly throughout the review period. The outcomes of multivariate analyses suggest that the male gender appears to have better response to HAART as seen in each of the multivariate models. The most important determinant of haemoglobin response was baseline haemoglobin values. In the haemoglobin-associated multivariate model, HAART is associated with an increase in haemoglobin over baseline values. A history of TB prior to HAART was a major factor in weight response and it is thought to be as a result of IRIS, which is the unmasking of latent infections as the immune system reconstitutes. CD4 values have no direct influence on weight however, but an increase in weight was observed in all therapy groups. Conclusion: Clinical and immunological parameters can be used to monitor response to HAART and predict treatment outcomes. These parameters can be organised into monitoring tools that will be useful in resource-limited areas. This study suggests that AZT-containing regimens appear not to result in anaemia and that symptomatic anaemia might need additional investigation. Treatment with TDF appeared to have shown the best possible response pattern more but patients on TDF therapy will have to be included in the study to justify this observation. / Dissertation (MSc)--University of Pretoria, 2012. / Clinical Epidemiology / unrestricted

A biodisponibilidade de um fármaco é o fator determinante da eficácia clínica e depende principalmente das seguintes etapas: liberação da substância ativa a partir da forma farmacêutica e absorção. Assim, o controle da extensão e da velocidade de absorção de um fármaco administrado por via oral depende basicamente de dois aspectos: solubilidade nos líquidos fisiológicos e permeabilidade através das membranas biológicas. Fundamentado nestas características, o Sistema de Classificação Biofarmacêutica (SCB) foi proposto como ferramenta que permite a classificação dos fármacos e tem como finalidade auxiliar nas bioisenções e na predição da biodisponibilidade in vivo. Neste sentido, o presente trabalho teve como objetivo avaliar a solubilidade da estavudina e a permeabilidade intestinal de fármacos antirretrovirais por meio do modelo de perfusão in situ. Os meios empregados nos estudos de solubilidade e dissolução intrínseca foram: água purificada, tampão pH 1,2, tampão pH 4,5, tampão pH 6,8 e tampão pH 7,5. Para a determinação da solubilidade pelo método do equilíbrio (técnica shake-flask), quantidades conhecidas do fármaco foram adicionadas em cada meio até atingir a saturação e esta mistura foi submetida à agitação de 150 rpm por 72 horas a 37°C. Para os ensaios de dissolução intrínseca, quantidade conhecida de estavudina foi compactada na matriz do aparato de Wood e submetida à dissolução em cada meio, sob agitação de 50 rpm a 37°C. A determinação da permeabilidade dos antirretrovirais foi realizada empregando o modelo de perfusão in situ em ratos machos Wistar. Uma porção do jejuno foi isolada e a solução de perfusão (pH 6,5) contendo o fármaco foi perfundida a um fluxo de 0,2 mL.min-1 a 37°C por 120 minutos. Os resultados obtidos referentes à solubilidade da estavudina pelo método do equilíbrio foram (em mg.mL-1): 146,49 (água), 149,22 (pH 4,5), 139,43 (pH 6,8) e 130,15 (pH 7,5). A determinação da razão dose:solubilidade (D:S) em cada meio permitiu a obtenção dos seguintes resultados (em mL): 0,27 (água), 0,27 (pH 4,5), 0,29 (pH 6,8) e 0,31 (pH 7,5). Tais dados indicaram que este fármaco apresenta alta solubilidade nos meios utilizados no estudo, exceto em meio pH 1,2, onde a estavudina apresentou instabilidade demonstrada pela presença de coloração e odor alterados, inviabilizando a determinação da solubilidade nestas condições. Os ensaios de dissolução intrínseca da estavudina permitiram a determinação das taxas de dissolução intrínseca (TDI), as quais foram (em mg/min/cm²): 2,3570 (água), 2,7389 (pH 1,2), 2,7590 (pH 4,5) e 2,5947 (pH 6,8), demonstrando que este fármaco apresenta alta velocidade de dissolução nos meios utilizados. Com relação ao estudo de permeabilidade por meio do modelo de perfusão in situ, nas condições experimentais empregadas, os resultados obtidos foram (em cm.s-1): 3,96 x 10-5 (estavudina), 3,08 x 10-5 (lamivudina) e 4,17 x 10-5 (zidovudina) sugerindo que os fármacos estavudina e zidovudina apresentam alta permeabilidade. Para a lamivudina não é descartada a possibilidade de ser considerada como fármaco de alta permeabilidade, mesmo apresentando resultado ligeiramente abaixo em relação aos outros dois antirretrovirais utilizados no estudo. / Drug\'s bioavaliability is a determinant factor of clinical efficacy and it depends on the following steps: release of active ingredient from the dosage form and absorption. Thus, control of extend and rate of absorption of a drug orally administered depends on two aspects: the drug solubility in physiological fluids and permeability across biological membranes. Based on these characteristics, the Biopharmaceutical Classification System (BCS) was proposed as a tool that allows the drug\'s classification and it assists in biowaiver and in vivo bioavailability prediction. The aim of this study was to evaluate stavudine solubility and intestinal permeability of antiretroviral drugs through the in situ perfusion model. The means employed in the solubility studies and intrinsic dissolution were: purified water, buffer pH 1.2, buffer pH 4.5, buffer pH 6.8 and buffer pH 7.5. For solubility study by equilibrium method (shake-flask technique), known amounts of the drug were added in each media to reach saturation and the mixture was subjected to agitation of 150 rpm for 72 hours at 37°C. For intrinsic dissolution test, known amount of stavudine has been compressed in the matrix of Wood\'s apparatus and subjected to dissolution in each media with agitation of 50 rpm at 37°C. Permeability evaluation of antiretroviral drugs was performed using the in situ perfusion model in male Wistar rats. A portion of jejunum was isolated and perfusion solution (pH 6.5) with the drug was perfused at 0.2 mL/min at 37°C for 120 minutes. Results of stavudine solubility by equilibrium method were (in mg/mL): 146.49 (water), 149.22 (pH 4.5), 139.43 (pH 6.8) and 130.15 (pH 7.5). Dose:solubility (D:S) ratio determinations allowed to obtain the following results (in mL): 0.27 (water), 0.27 (pH 4.5), 0.29 (pH 6.8) and 0.31 (pH 7.5). These results indicate that stavudine has high solubility in the means employed in this study, except in buffer pH 1.2, where stavudine showed instability demonstrated by presence of stain and odor changed, which prevented the determination of solubility in these conditions. The intrinsic dissolution study allowed the determination of intrinsic dissolution rates (IDR), which were (in mg/min/cm²): 2.3570 (water), 2.7389 (pH 1.2), 2.7590 (pH 4.5) and 2.5947 (pH 6.8), demonstrating that this drug has a high dissolution rate in each media used. In permeability study through the in situ perfusion model, under experimental conditions adopted, the results obtained were (in cm/s): 3.96 x 10-5 (stavudine), 3.08 x 10-5 (lamivudine) and 4.17 x 10-5 (zidovudine), suggesting that stavudine and zidovudine have high permeability. It\'s possible that lamivudine might be considered high permeability drug, although its effective permeability result was slightly lower compared to effective permeability of stavudine and zidovudine.

A biodisponibilidade de um fármaco é o fator determinante da eficácia clínica e depende principalmente das seguintes etapas: liberação da substância ativa a partir da forma farmacêutica e absorção. Assim, o controle da extensão e da velocidade de absorção de um fármaco administrado por via oral depende basicamente de dois aspectos: solubilidade nos líquidos fisiológicos e permeabilidade através das membranas biológicas. Fundamentado nestas características, o Sistema de Classificação Biofarmacêutica (SCB) foi proposto como ferramenta que permite a classificação dos fármacos e tem como finalidade auxiliar nas bioisenções e na predição da biodisponibilidade in vivo. Neste sentido, o presente trabalho teve como objetivo avaliar a solubilidade da estavudina e a permeabilidade intestinal de fármacos antirretrovirais por meio do modelo de perfusão in situ. Os meios empregados nos estudos de solubilidade e dissolução intrínseca foram: água purificada, tampão pH 1,2, tampão pH 4,5, tampão pH 6,8 e tampão pH 7,5. Para a determinação da solubilidade pelo método do equilíbrio (técnica shake-flask), quantidades conhecidas do fármaco foram adicionadas em cada meio até atingir a saturação e esta mistura foi submetida à agitação de 150 rpm por 72 horas a 37°C. Para os ensaios de dissolução intrínseca, quantidade conhecida de estavudina foi compactada na matriz do aparato de Wood e submetida à dissolução em cada meio, sob agitação de 50 rpm a 37°C. A determinação da permeabilidade dos antirretrovirais foi realizada empregando o modelo de perfusão in situ em ratos machos Wistar. Uma porção do jejuno foi isolada e a solução de perfusão (pH 6,5) contendo o fármaco foi perfundida a um fluxo de 0,2 mL.min-1 a 37°C por 120 minutos. Os resultados obtidos referentes à solubilidade da estavudina pelo método do equilíbrio foram (em mg.mL-1): 146,49 (água), 149,22 (pH 4,5), 139,43 (pH 6,8) e 130,15 (pH 7,5). A determinação da razão dose:solubilidade (D:S) em cada meio permitiu a obtenção dos seguintes resultados (em mL): 0,27 (água), 0,27 (pH 4,5), 0,29 (pH 6,8) e 0,31 (pH 7,5). Tais dados indicaram que este fármaco apresenta alta solubilidade nos meios utilizados no estudo, exceto em meio pH 1,2, onde a estavudina apresentou instabilidade demonstrada pela presença de coloração e odor alterados, inviabilizando a determinação da solubilidade nestas condições. Os ensaios de dissolução intrínseca da estavudina permitiram a determinação das taxas de dissolução intrínseca (TDI), as quais foram (em mg/min/cm²): 2,3570 (água), 2,7389 (pH 1,2), 2,7590 (pH 4,5) e 2,5947 (pH 6,8), demonstrando que este fármaco apresenta alta velocidade de dissolução nos meios utilizados. Com relação ao estudo de permeabilidade por meio do modelo de perfusão in situ, nas condições experimentais empregadas, os resultados obtidos foram (em cm.s-1): 3,96 x 10-5 (estavudina), 3,08 x 10-5 (lamivudina) e 4,17 x 10-5 (zidovudina) sugerindo que os fármacos estavudina e zidovudina apresentam alta permeabilidade. Para a lamivudina não é descartada a possibilidade de ser considerada como fármaco de alta permeabilidade, mesmo apresentando resultado ligeiramente abaixo em relação aos outros dois antirretrovirais utilizados no estudo. / Drug\'s bioavaliability is a determinant factor of clinical efficacy and it depends on the following steps: release of active ingredient from the dosage form and absorption. Thus, control of extend and rate of absorption of a drug orally administered depends on two aspects: the drug solubility in physiological fluids and permeability across biological membranes. Based on these characteristics, the Biopharmaceutical Classification System (BCS) was proposed as a tool that allows the drug\'s classification and it assists in biowaiver and in vivo bioavailability prediction. The aim of this study was to evaluate stavudine solubility and intestinal permeability of antiretroviral drugs through the in situ perfusion model. The means employed in the solubility studies and intrinsic dissolution were: purified water, buffer pH 1.2, buffer pH 4.5, buffer pH 6.8 and buffer pH 7.5. For solubility study by equilibrium method (shake-flask technique), known amounts of the drug were added in each media to reach saturation and the mixture was subjected to agitation of 150 rpm for 72 hours at 37°C. For intrinsic dissolution test, known amount of stavudine has been compressed in the matrix of Wood\'s apparatus and subjected to dissolution in each media with agitation of 50 rpm at 37°C. Permeability evaluation of antiretroviral drugs was performed using the in situ perfusion model in male Wistar rats. A portion of jejunum was isolated and perfusion solution (pH 6.5) with the drug was perfused at 0.2 mL/min at 37°C for 120 minutes. Results of stavudine solubility by equilibrium method were (in mg/mL): 146.49 (water), 149.22 (pH 4.5), 139.43 (pH 6.8) and 130.15 (pH 7.5). Dose:solubility (D:S) ratio determinations allowed to obtain the following results (in mL): 0.27 (water), 0.27 (pH 4.5), 0.29 (pH 6.8) and 0.31 (pH 7.5). These results indicate that stavudine has high solubility in the means employed in this study, except in buffer pH 1.2, where stavudine showed instability demonstrated by presence of stain and odor changed, which prevented the determination of solubility in these conditions. The intrinsic dissolution study allowed the determination of intrinsic dissolution rates (IDR), which were (in mg/min/cm²): 2.3570 (water), 2.7389 (pH 1.2), 2.7590 (pH 4.5) and 2.5947 (pH 6.8), demonstrating that this drug has a high dissolution rate in each media used. In permeability study through the in situ perfusion model, under experimental conditions adopted, the results obtained were (in cm/s): 3.96 x 10-5 (stavudine), 3.08 x 10-5 (lamivudine) and 4.17 x 10-5 (zidovudine), suggesting that stavudine and zidovudine have high permeability. It\'s possible that lamivudine might be considered high permeability drug, although its effective permeability result was slightly lower compared to effective permeability of stavudine and zidovudine.