PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “BIOPHARMACEUTICS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,531 records · Page 85Linked to original sources
PubMed1979

Blood levels of neuroleptic drugs in nonresponding chronic schizophrenic patients.

Blood levels of butaperazine were measured in schizophrenic patients who were chronic nonresponders to their psychotropic medication. The blood levels were compared with those in patients who had shown a better clinical response to this neuroleptic. Nonresponders had two to seven times lower levels of butaperazine in plasma and RBCs after a single dose or chronic dosing. Some of the patients later treated with thioridazine or haloperidol had lower plasma levels of these neuroleptics also. No significant differences were found between nonresponders and relative responders in either the alpha- or beta-phase half-life of butaperazine in plasma and RBCs after administration of a single dose of the drug. Butaperazine and thioridazine levels were not related to previously administered amounts of neuroleptic drugs. These findings do not support the hypothesis that low blood levels are the result of faster systemic metabolism of the drug after it reaches the central circulation. Our results suggest that low blood levels of neuroleptics may be one important factor in the poor clinical response of some chronic schizophrenic patients.

Adult↗
PubMed1984

Characterization and prediction of lithium blood levels and clearances.

Mathematical simulations and nonlinear numerical methods for characterizing the serum elimination half-life, volume of distribution, and renal clearance of lithium after multiple oral doses of lithium carbonate and two or more blood level determinations were constructed and adapted for clinical use. These characteristics were measured for 24 inpatients; predictions were made with the simulation and compared with actual succeeding blood levels. The average elimination half-life of 25.9 hours was compared with half-lives reported after single oral doses. Average and median errors of prediction were negligible; the root mean square error was 0.12 mEq/L, near the coefficient of variation of 0.082 mEq/L. The correlation between predicted and observed levels (r) was .82; a small systematic effect of weight was found.

Administration, Oral↗
PubMedDate not supplied

LC/MS applications in drug development.

The combination of high-performance liquid chromatography and mass spectrometry (LC/MS) has had a significant impact on drug development over the past decade. Continual improvements in LC/MS interface technologies combined with powerful features for structure analysis, qualitative and quantitative, have resulted in a widened scope of application. These improvements coincided with breakthroughs in combinatorial chemistry, molecular biology, and an overall industry trend of accelerated development. New technologies have created a situation where the rate of sample generation far exceeds the rate of sample analysis. As a result, new paradigms for the analysis of drugs and related substances have been developed. The growth in LC/MS applications has been extensive, with retention time and molecular weight emerging as essential analytical features from drug target to product. LC/MS-based methodologies that involve automation, predictive or surrogate models, and open access systems have become a permanent fixture in the drug development landscape. An iterative cycle of "what is it?" and "how much is there?" continues to fuel the tremendous growth of LC/MS in the pharmaceutical industry. During this time, LC/MS has become widely accepted as an integral part of the drug development process. This review describes the utility of LC/MS techniques for accelerated drug development and provides a perspective on the significant changes in strategies for pharmaceutical analysis. Future applications of LC/MS technologies for accelerated drug development and emerging industry trends are also discussed.

Amino Acid Sequence↗
PubMed2000

Carbamazepine level-A in vivo-in vitro correlation (IVIVC): a scaled convolution based predictive approach.

A method is presented for prediction of the systemic drug concentration profile from in vitro release/dissolution data for a drug formulation. The method is demonstrated using four different tablet formulations containing 200 mg carbamazepine (CZM), each administered in a four way cross-over manner to 20 human subjects, with 15 blood samples drawn to determine the resulting concentration profile. Amount versus time dissolution data were obtained by a 75 rpm paddle method for each formulation. Differentiation, with respect to time, of a monotonic quadratic spline fitted to the dissolution data provided the dissolution rate curve. The dissolution curve was through time and magnitude scaling mapped into a drug concentration curve via a convolution by a single exponential, and the estimated unit impulse response function. The method was tested by cross-validation, where the in vivo concentration profiles for each formulation were predicted based on correlation parameters determined from in vivo-in vitro data from the remaining three formulations. The mean prediction error (MPE), defined as the mean value of 100% x(observed-predicted)/observed was calculated for all 240 cross-validation predictions. The mean values of MPE were in the range of 10-36% (average 22%) with standard deviations (S.D.s) in the range of 9-33% (average 13%), indicating a good prediction performance of the proposed in vivo-in vitro correlation (IVIVC) method.

Analgesics, Non-Narcotic↗
PubMedDate not supplied

Sustained release properties of the once daily theophylline capsule BY912 as compared with Theo-24 capsules.

In a multiple dose cross-over experiment in 12 healthy male adults the bioavailability and sustained release characteristics of new once daily BY912 400 mg theophylline capsules (= B, Byk Gulden Research Laboratories, FRG) were studied using Theo-24 capsules (= T, Searle & Co., USA) as reference. Both products were given once daily for a period of 7 days as an 800 mg theophylline dose at 8 am, half an hour after a standardized breakfast. Theophylline concentrations in plasma were measured on days 1, 6, and 7 using high-performance liquid chromatography. Significantly better sustained release characteristics, resulting in longer plateau time (t75%, 11.6 vs 9.2 h on day 6 and 13.1 vs 8.8 h on day 7) and smaller per cent peak-trough fluctuation in the steady state (per cent PTF, 80 vs 103 per cent on day 6 and 66 vs 100 per cent on day 7), were found for B in comparison with T. The extent of absorption on both days, however, was smaller for B compared with T (relative bioavailability 84 per cent and 81 per cent, respectively). In conclusion, the absorption of theophylline from B resulted in a more extended shape of the plateau phase, indicating better sustained release characteristics. The extent of absorption, however, over the dosing intervals was more complete with T.

Adult↗
PubMed2005

Superior safety in noninferiority trials.

Noninferiority of a new treatment to a reference treatment with respect to efficacy is usually associated with the superiority of the new treatment to the reference treatment with respect to other aspects not associated with efficacy. When the superiority of the new treatment to the reference treatment is with respect to a specified safety variable, it may be necessary to perform the between-treatment comparisons. The efficacy and safety comparisons may be considered separately or simultaneous comparisons may be performed. Here techniques are discussed for the simultaneous consideration of both aspects.

Biopharmaceutics↗
PubMed2005

Biostatistical assessment of mutagenicity studies by including the positive control.

Statistical analysis plays a fundamental part in the evaluation of mutagenicity experiments. However, a statistically significant or non-significant test result without incorporating the biological relevance cannot be a valid scientific criterion for concluding a positive or negative effect of the underlying compound (Hauschke et al., 1997). The classification of an experiment as being negative or positive should be based also on the magnitude of the responses in the positive control. We address the problem of determining the maximum safe dose by incorporating a biologically meaningful threshold value, which is expressed as a fraction of the difference between positive and vehicle control.

Biometry↗
PubMed2005

A regulatory perspective on choice of margin and statistical inference issue in non-inferiority trials.

Without a placebo arm, any non-inferiority inference involving assessment of the placebo effect under the active control trial setting is difficult. The statistical risk for falsely concluding non-inferiority cannot be evaluated unless the constancy assumption approximately holds that the effect of the active control under the historical trial setting where the control effect can be assessed carries to the noninferiority trial setting. The constancy assumption cannot be checked because of missing the placebo arm in the non-inferiority trial. Depending on how serious the violation of the assumption is thought to be, one may need to seek an alternative design strategy that includes a cushion for a very conservative non-inferiority analysis or shows superiority of the experimental treatment over the control. Determination of the non-inferiority margin depends on what objective the non-inferiority analysis is intended to achieve. The margin can be a fixed margin or a margin functionally defined. Between-trial differences always exist and need to be properly considered.

Biopharmaceutics↗
PubMed2005

Choice of delta: requirements and reality--results of a systematic review.

An essential problem in planning clinical non-inferiority or equivalence studies is the specification of the 'irrelevant difference' (irrelevance margin; delta). This quantifies the amount of non-inferiority or difference, respectively, between a new test therapy and an established standard treatment which is to be considered as tolerable. In the past, most recommendations and guidelines for clinical non-inferiority and equivalence studies contained only general statements and formulations concerning the specification of delta. The current unsatisfactory situation was the reason for performing a systematic review of published clinical non-inferiority and equivalence studies. It was the aim to gain an overview on the irrelevance margins used in such studies, and on reasons for choosing the particular margins. For the sake of comparability, the irrelevance margins were converted into standardized differences and odds ratios. Overall, there were 332 non-inferiority or equivalence trials obtained by means of an extensive literature search. The results of the systematic review show that current requirements on the choice of delta and the reality of recent clinical non-inferiority and equivalence trials differ substantially. In about one half of the trials a difference of 0.5 standard deviations or more was regarded as 'irrelevant' explicitly or implicitly. Estimates of standard-placebo differences formed the basis of the irrelevance margin in less than every tenth trial. Reasons for this very low proportion might be (1) the possibly resulting very small irrelevance margins, and (2) unsolved problems of the requirements themselves. Overall, it seems that a more global definition of 'irrelevance' might be warranted.

Biopharmaceutics↗
PubMed2005

Problems with existing procedures to calculate exact unconditional P-values for non-inferiority/superiority and confidence intervals for two binomials and how to resolve them.

Recently several papers have been published that deal with the construction of exact unconditional tests for non-inferiority and confidence intervals based on the approximative unconditional restricted maximum likelihood test for two binomial random variables. Soon after the papers have been published the commercially available software for exact tests StatXact has incorporated the new methods. There are however gaps in the proofs which since have not been resolved adequately. Further it turned out that the methods for testing non-inferiority are not coherent and test for non-inferiority can easily come to different conclusions compared to the confidence interval inclusion rule. In this paper, a proposal is made how to resolve the open problems. Berger and Boos (1994) developed the confidence interval method for testing equality of two proportions. StatXact (Version 5) has extended this method for shifted hypotheses. It is shown that at least for unbalanced designs (i.e. largely different sample sizes) the Berger and Boos method can lead to controversial results.

Biopharmaceutics↗
PubMed2005

Testing superiority and non-inferiority hypotheses in active controlled clinical trials.

Switching between testing for superiority and non-inferiority has been an important statistical issue in the design and analysis of active controlled clinical trial. In practice, it is often conducted with a two-stage testing procedure. It has been assumed that there is no type I error rate adjustment required when either switching to test for non-inferiority once the data fail to support the superiority claim or switching to test for superiority once the null hypothesis of non-inferiority is rejected with a pre-specified non-inferiority margin in a generalized historical control approach. However, when using a cross-trial comparison approach for non-inferiority testing, controlling the type I error rate sometimes becomes an issue with the conventional two-stage procedure. We propose to adopt a single-stage simultaneous testing concept as proposed by Ng (2003) to test both non-inferiority and superiority hypotheses simultaneously. The proposed procedure is based on Fieller's confidence interval procedure as proposed by Hauschke et al. (1999).

Biopharmaceutics↗
PubMed2005

Statistical methods for the analysis of two-arm non-inferiority trials with binary outcomes.

The aim of this contribution is to give an overview of approaches to testing for non-inferiority of one out of two binomial distributions as compared to the other in settings involving independent samples (the paired samples case is not considered here but the major conclusions and recommendations can be shown to hold for both sampling schemes). In principle, there is an infinite number of different ways of defining (one-sided) equivalence in any multiparameter setting. In the binomial two-sample problem, the following three choices of a measure of dissimilarity between the underlying distributions are of major importance for real applications: the odds ratio (OR), the relative risk (RR), and the difference (DEL) of both binomial parameters. It is shown that for all three possibilities of formulating the hypotheses of a non-inferiority problem concerning two binomial proportions, reasonable testing procedures providing exact control over the type-I error risk are available. As a particularly useful and versatile way of handling mathematically nonnatural parametrizations like RR and DELTA, the approach through Bayesian posterior probabilities of hypotheses with respect to some non-informative reference prior has much to recommend it. In order to ensure that the corresponding testing procedure be valid in the classical, i.e. frequentist sense, it suffices to use straightforward computational techniques yielding suitably corrected nominal significance levels. In view of the availability of testing procedures with satisfactory properties for all parametrizations of main practical interest, the discussion of the pros and cons of these methods has to focus on the question of which of the underlying measures of dissimilarity should be preferred on grounds of logic and intuition. It is argued that the OR clearly merits to be given preference also with regard to this latter kind of criteria since the non-inferiority hypotheses defined in terms of the other parametric functions are bounded by lines which cross the boundaries of the parameter space. From this fact, we conclude that the exact Fisher type test for one-sided equivalence provides the most reasonable approach to the confirmatory analysis of non-inferiority trials involving two independent samples of binary data. The marked conservatism of the nonrandomized version of this test can largely be removed by using a suitably increased nominal significance level (depending, in addition to the target level, on the sample sizes and the equivalence margin), or by replacing it with a Bayesian test for non-inferiority with respect to the odds ratio.

Biopharmaceutics↗