Didanosine (ddI) is a component of highly active antiretroviral therapy drug combinations, used especially in resource-limited settings and in zidovudine-resistant patients. The population pharmacokinetics of ddI was evaluated in 48 healthy volunteers enrolled in two bioequivalence studies. These data, along with a set of co-variates, were the subject of a nonlinear mixed-effect modeling analysis using the NONMEM program. A two-compartment model with first order absorption (ADVAN3 TRANS3) was fitted to the serum ddI concentration data. Final pharmacokinetic parameters, expressed as functions of the co-variates gender and creatinine clearance (CL CR), were: oral clearance (CL = 55.1 + 240 x CL CR + 16.6 L/h for males and CL = 55.1 + 240 x CL CR for females), central volume (V2 = 9.8 L), intercompartmental clearance (Q = 40.9 L/h), peripheral volume (V3 = 62.7 + 22.9 L for males and V3 = 62.7 L for females), absorption rate constant (Ka = 1.51/h), and dissolution time of the tablet (D = 0.43 h). The intraindividual (residual) variability expressed as coefficient of variation was 13.0%, whereas the interindividual variability of CL, Q, V3, Ka, and D was 20.1, 75.8, 20.6, 18.9, and 38.2%, respectively. The relatively high (>30%) interindividual variability for some of these parameters, observed under the controlled experimental settings of bioequivalence trials in healthy volunteers, may result from genetic variability of the processes involved in ddI absorption and disposition.

Bioanalytical data from a bioequivalence study were used to develop limited-sampling strategy (LSS) models for estimating the area under the plasma concentration versus time curve (AUC) and the peak plasma concentration (Cmax) of 4-methylaminoantipyrine (MAA), an active metabolite of dipyrone. Twelve healthy adult male volunteers received single 600 mg oral doses of dipyrone in two formulations at a 7-day interval in a randomized, crossover protocol. Plasma concentrations of MAA (N = 336), measured by HPLC, were used to develop LSS models. Linear regression analysis and a "jack-knife" validation procedure revealed that the AUC0-<FONT FACE=Symbol>¥</FONT> and the Cmax of MAA can be accurately predicted (R²>0.95, bias <1.5%, precision between 3.1 and 8.3%) by LSS models based on two sampling times. Validation tests indicate that the most informative 2-point LSS models developed for one formulation provide good estimates (R²>0.85) of the AUC0-<FONT FACE=Symbol>¥</FONT> or Cmax for the other formulation. LSS models based on three sampling points (1.5, 4 and 24 h), but using different coefficients for AUC0-<FONT FACE=Symbol>¥</FONT> and Cmax, predicted the individual values of both parameters for the enrolled volunteers (R²>0.88, bias = -0.65 and -0.37%, precision = 4.3 and 7.4%) as well as for plasma concentration data sets generated by simulation (R²>0.88, bias = -1.9 and 8.5%, precision = 5.2 and 8.7%). Bioequivalence assessment of the dipyrone formulations based on the 90% confidence interval of log-transformed AUC0-<FONT FACE=Symbol>¥</FONT> and Cmax provided similar results when either the best-estimated or the LSS-derived metrics were used.

A freqüência e descrição dos efeitos secundários à aplicação subcutânea da vacina antímalãrica SPf66 e placebo, são notificadas para cada dose nos participantes do estudo da eficácia vacinai no Brasil. Efeitos colaterais avaliados duas horas após a aplicação dos preparados foram detectados em 8,0%, 30,2% e 8,8% para a 1ª, 2ª e 3ª doses, respectivamente, no grupo de vacinados; e em 7,0%, 8,5% e 2,9% no grupo que recebeu o placebo. Reações tais como inflamação leve, nódulo e dor freqüentemente acompanhadas de prurido, foram as reações locais mais freqüentes em ambos os grupos (3,8%, 29,1% e 8,5% no gmpo vacinado, e 4,0%, 7,6% e 2,5% no grupo placebo). No grupo que recebeu a vacina, as reações locais foram mais freqüentes em mulheres após a 2ª dose. Os efeitos colaterais sistêmicos basearam-se em sinais e sintomas referidos pelos participantes. Foram mais freqüentes após a aplicação da 1ª dose em ambos os grupos (4,3%, no grupo de vacinados e, 3,0%, no grupo placebo). Alguns participantes referiram mialgias e febre. Nenhum efeito colateral grave foi detectado em nenhuma dose de aplicação ou grupo.

The frequency and description of side effects secondaiy to the subcutaneous application of SPf66 malaria vaccine and placebo are reported for each dose of application in the participants of the vaccine efficacy trial in Brazil. Side effects evaluated two hours after each application were detected in 8.0%, 30.2% and 8.8%, for the Is', and 3"' dose, respectively, in the SPf66group, and in 7.0%, 8.5% and 2.9% in the placebo group. Local reactions such as mild inflammation, nodule and pain or erythema frequently accompanied by pruritus were the most common reactions detected in both groups (3-8%, 29.1% and 8.5% in the SPf66 group and 4.0%, 7.6% and 2.5% in the placebo group). Among vaccinees, local side effects after the 2nd dose were more frequent in females. Systemic side effects were expressed mainly through general symptoms referred by the participants and were most frequent after the 1st dose in both groups (4.3% in the SPf66 group and 3-0% in the placebo group). Muscle aches and fever were refewred by few participants. No severe adverse reactions were detected for either dose of application or group.

O presente artigo descreve a população de estudo e o desenho do ensaio de campo de fase III da vacina sintética SPf66 no Brasil. São avaliados os princípios básicos de validade e precisão, essenciais para a estimação adequada da eficácia vacinal. Os resultados da análise exploratória de dados são discutidos assim como, a abordagem analítica para a estimação da eficácia vacinal. Este trabalho fornece o marco conceitual para futuras publicações.

This paper describes the study population and the study design of the phase III field trial of the SPf66 vaccine in Brazil. Assessment of validity and precision principles necessary for the appropriate evaluation of the protective effect of the vaccine are discussed, as well as the results of the preliminary analyses of the gathered data. The analytical approach for the estimation of the protective effect of the vaccine is presented. This paper provides the conceptual framework for future publications.