Clinical trials absorption testing

The Phase I clinical trial is the first experiment in which a drug is tested on the human body. The primary aim of the trial is to assess the safety of the new drug. Other areas of study include pharmacokinetics (absorption, distribution, metabolism, and excretion) and pharmacodynamics. 

Foreign clinical results are acceptable except in areas where there are immunological and ethnic differences between Japanese and foreigners. The ethnic factors are divided into two components intrinsic factors such as racial factors and physiological differences and extrinsic factors, which include cultural and environmental issues. In these cases, the MHLW may require that some bridging comparative clinical trials be performed with dose ranging protocols. This will enable absorption, distribution, metabolism, and excretion studies to be carried out on Japanese individuals and provide better dosage and indication for the Japanese people. The MHLW also requires that application be accompanied by one year of real-time stability data and that sterility test results be included. 

Drug metabolism and pharmacokinetic (DMPK) studies are used to show how the concentrations of the drug and its metabolites vary with the administered dose of the drug and the time from administration. They are normally carried out using suitable animal species and in humans in Phase I trials. The information obtained from animal studies is used to determine safe dose levels for use in the Phase I clinical trials in humans. However, the accuracy of the data obtained from animal tests is limited, since it is obtained by extrapolation. In addition, it is necessary to determine the dose that just saturates the absorption and elimination processes so that the toxicological and pharmacological events may be correctly interpreted. 

The standardized guidelines have been compiled to cover test methods in animal studies and in vitro studies on absorption, distribution, metabolism cind excretion in the Notification No. 496 of the PAB in 1998. The guidelines can be applicable for the drugs to be submitted after October 1999. The following principles should be considered in order to select the most appropriate methods bcised on the characteristics of test substance. It is required that the exposure data related to toxicological studies be obtained before the first human study and other pharmacokinetic data before the completion of Phcise I study in principle in accordance with the guidelines on nonclinical safety studies for conducting clinical trials (Notification No. 1019 of the PAB, 1998). 

A DNA vaccine candidate that has successfully passed all preclinical hurdles needs to be tested clinically by a three-phased scheme as outlined in Chapter 4. As defined by a European Council directive, a clinical trial means ... any investigation in human subjects intended to discover or verify the clinical, pharmacological and/or other pharmacodynamic effects of. .. investigational medicinal product(s), and/or to identify any adverse reactions. .. and/or to study absorption, distribution. 

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