Pharmacokinetics of a novel antiarrhythmic drug, actisomide

Natural and commercial antibiotic comparison with drugs modeling Cell Integrity Cell Stability of Bio-Kinetics Changes under Morphological Topographies cells with lower Toxicological Characteristics for multidrug resistances problem

Antibacterial drug-resistant strains are a serious problem of bacterial treatments nowadays and have a concern. The plant exacts of Adhatoda vasica and Calotropis procera are well-known for their role as antibiotic agents. The extraction of novel antibiotic compounds was done by HPLC-DAD, their yield is quantified by numerous solvents. The complete biological activity with antioxidants, bio-kinematicof four compounds of B-Sitosteryl linoleate, Myristyl diglucoside, D-Triglucopyranoside, and S- allylcysteine acids were studied. The supercritical fluid extraction techniques were the best strategies for higher yield, accuracy clarity, and inter, intra process of all four compounds. A. vasica and C. procera samples and investigated in six different solvents. D-Triglucopyranoside (13.81 ± 0.48%), Myristyl diglucoside (11.81 ± 0.41%), B- Sitosteryl linoleate (12.81 ± 0.48%), and s-allylcysteine acids (14.81 ± 0.31%) were higher. The design and action of compounds were applied to proper compartmental pharmacokinetic modelling for in-depth design understanding. The morphology and structure of bacterial cells with the extracted compounds upheld the permeability of cell membranes, membrane integrity, and membrane potential and lower the bacterial binding capacity the infectious index was measured in transmission electron microscopy (TEM) and their alteration process. Plants have well upheld the cellular permeability The toxicity test was performed on both extracted samples with concentrations (1, 0.4, and 0.8%). The areas under plasma half-life of compounds with their solubility, abortion level were higher in four compounds showed the potential of novel antibiotics. The novel medicinal plants used as antibiotics could be the best sources of infection control as a source of future medicines with antibacterial potential solving multidrug issues of bacteria in the world.

Prediction of drug concentration-time data in humans from animals: a comparison of three methods

The main objective of this work is to evaluate three methods to predict concentration-time data of drugs in humans in a multi-compartment system using animal pharmacokinetic parameters following intravenous administration. The prediction of concentration-time data in humans in a multi-compartment system was based on two proposed methods of Mordenti. The third method was based on the assumption that all drugs follow a single-compartment system. Ten drugs from the literature were chosen that were described by two-compartment model in both human and animals. Two-compartment model parameters (CL, V(c), V(ss), V(β), α, A, β and B) of at least 3 animals were scaled to humans and then were used to predict plasma concentrations-time data in humans. Allometrically scaled pharmacokinetic parameters from animals were also used to predict human profile using one-compartment model as a comparison. The results indicated that in a multi-compartment system, application of pharmacokinetic constants provided better prediction of concentration-time data in humans than the assumption that all drugs follow a single-compartment model. Both the proposed methods of Mordenti provided almost similar concentration-time profiles for most of the drugs. For some drugs, predicted α values were substantially higher than the observed values. This prediction error in α resulted in under-prediction of drug concentrations in distribution phase. In order to reduce the prediction error in α, Waijma's method for the prediction of α was modified which resulted in an improved prediction of concentration-time data in humans. Overall, Mordenti's proposed 2 methods and where necessary by modifying Waijma's method for the prediction of α can be used for reasonably accurate prediction of concentration-time data of drugs in humans.

Application of fixed exponent 0.75 to the prediction of human drug clearance: an inaccurate and misleading concept

Considering the controversy surrounding the exponent of 0.75 for the prediction of human drug clearance and lack of any systematic evaluation of the aforementioned proposal, the objective of this study was to determine whether the exponent 0.75 is indeed the most suitable exponent for the prediction of human drug clearance as compared to allometric scaling using the rule of exponents (ROE). Three methods were used to predict human drug clearance. Besides evaluating the exponent of 0.75, an arbitrarily selected exponent of 0.65 was also tested. ROE was also used to predict human drug clearance, and predicted values by all three methods were compared with observed human drug clearance. The results indicate that the exponent 0.75 is not the best approach for the prediction of human drug clearance. Both exponents 0.75 and 0.65 predicted human drug clearance with uncertainty, although on average the prediction of human drug clearance by 0.65 was better than the exponent 0.75. ROE provided far more accurate prediction of human drug clearance than either of the exponents. Although exponent 0.75 occasionally provided a good prediction of human drug clearance for a given drug for a given species, overall, the method is highly erratic and unreliable.

Prediction of human pharmacokinetics from animal data and molecular structural parameters using multivariate regression analysis: oral clearance

The aim of the study reported here was to develop a regression equation for predicting oral clearance of various kinds of drugs in humans using experimental data from rats and dogs and molecular structural parameters. The data concerning the oral clearance of 87 drugs from rats, dogs, and humans were obtained from literature. The compounds have various structures, pharmacological activities, and pharmacokinetic characteristics. In addition, the molecular weight, calculated partition coefficient (c log P), and the number of hydrogen bond acceptors were used as possible descriptors related to oral clearance in human. Multivariate regression analyses, multiple linear regression analysis, and the partial least squares (PLS) method were used to predict oral clearance in human, and the predictive performances of these techniques were compared by allometric approaches, which have been used in interspecies scaling. Interaction terms were also introduced into the regression analysis to evaluate the nonlinear relationship. For the data set used in this study, the PLS model with the tertiary term descriptors gave the best predictive performance, and the value of the squared cross-validated correlation coefficient (q(2)) was 0.694. This PLS model, using animal oral clearance data for only two species and easily calculated molecular structural parameters, can generally predict oral clearance in human better than the allometric approaches. In addition, the molecular structural parameters and the interaction term descriptors were useful for predicting oral clearance in human by PLS. Another advantage of this PLS model is that it can be applied to drugs with various characteristics.

Prediction of human pharmacokinetics from animal data and molecular structural parameters using multivariate regression analysis: volume of distribution at steady state

The aim of this study was to develop a regression equation for predicting volume of distribution at steady state (Vd(ss)) in humans to enable application to various types of drugs using animal experimental data for rats and dogs and some molecular structural parameters. The Vd(ss) data for rats, dogs and humans of 64 drugs were obtained from literature. The compounds have various structures, pharmacological activities and pharmacokinetic characteristics. In addition, the molecular weight, calculated partition coefficient (clogP), and the number of hydrogen bond acceptors were used as possible descriptors related to the Vd(ss) in humans. Multivariate regression analyses, multiple linear regression analysis and the partial least squares (PLS) method were used to predict Vd(ss) in humans. Interaction terms were also introduced into the regression analysis to evaluate the non-linear relationship. For the data set used in the present study, PLS with quadratic term descriptors gave the best predictive performance. The PLS model using Vd(ss) data for only two animal species and using easily calculated structural parameters could generally predict Vd(ss) in humans better than an allometric method. In addition, the PLS model with only animal data gave almost the same predictive performance as the PLS model with quadratic term descriptors. This model may be easier to use and be practical in a realistic situation, and could predict Vd(ss) in humans better than the allometric method.

Drug disposition viewed in terms of the fractal volume of distribution

PURPOSE

(i) Evaluate the predictive performance of the fractal volume of drug distribution, v(f), (Pharm. Res.18, 1056, 2001), (ii) develop the concept of the fractal clearance, CLf, which is the clearance analogue of v(f), (iii) examine the utility of CLf in allometric studies, (iv) develop allometric relationships for the elimination half-life, t1/2, and (v) evaluate the use of v(f) and CLf in predicting the volume of drug distribution, Vap, clearance, CL, and elimination half-life, t1/2.

METHODS

Estimates for v(f) of various drugs were obtained and correlated with body mass using data only from animal species. A comparison was made between the predicted and actual v(f) values for humans. For a variety of animal species CLf values were estimated from the equation: [equation: see text]. The allometric equations developed using CLf were compared with other allometric approaches. Allometric equations were also developed for t1/2 utilizing the allometric relationships of v(f) and CLf,

RESULTS

The predicted estimates of v(f) were very close to the actual values and the correlation exhibited favorable statistical properties. The values of the allometric exponents for CLf were found to be close to 0.75. The predictive performance for CL using the allometric equations for CLf in conjunction with the rule of exponents was found to be better than the currently considered most accurate allometric approaches. The values of the allometric exponents for t1/2 were found to be close to 0.25

CONCLUSION

The predictive ability of v(f) is high; predictions for Vap based on v(f) values are better than the current approaches. CLf expressed a good behavior both in prospective and retrospective analysis. The allometric exponents, 0.75, 0.25 for CLf and t1/2, respectively, agree with the theoretical expected values.

Interspecies scaling: predicting oral clearance in humans

The objective of this study was to test the interspecies scaling approach for a wide variety of drugs to predict oral clearance in humans from animal data. This study is an attempt to evaluate whether the rule of exponents of Mahmood and Balian for the prediction of systemic clearance can also be applied for the prediction of oral clearance in humans. Three different methods were used to generate log-log plots to scale up the clearance values: (1) clearance versus body weight (simple allometric equation), (2) the product of clearance and maximum life-span potential (MLP) versus body weight, and (3) the product of clearance and brain weight versus body weight. Data from 32 drugs were analyzed, and it was concluded that the oral clearance of drugs could be best predicted using one of the allometric equations.

Fractal volume of drug distribution: it scales proportionally to body mass

PURPOSE

To develop the physiologically sound concept of fractal volume of drug distribution, vf, and evaluate its utility and applicability in interspecies pharmacokinetic scaling.

METHODS

Estimates for vf of various drugs in different species were obtained from the relationship: vf = (v - Vpl)(Vap - Vpl)/V + Vpl where v is the total volume of the species (equivalent to its total mass assuming a uniform density Ig/mL), Vpl is the plasma volume of the species and Vap is the conventional volume of drug distribution. This equation was also used to calculate the fractal analogs of various volume terms of drug distribution (the volume of central compartment, Vc, the steady state volume of distribution, Vss, and the volume of distribution following pseudodistribution equilibrium, Vz). The calculated fractal volumes of drug distribution were correlated with body mass of different mammalian species and allometric exponents and coefficients were determined.

RESULTS

The calculated values of vf for selected drugs in humans provided meaningful and physiologically sound estimates for the distribution of drugs in the human body. For all fractal volume terms utilized, the allometric exponents were found to be either one or close to unity. The estimates of the allometric coefficients were found to be in the interval (0,1). These decimal values correspond to a fixed fraction of the fractal volume term relative to body mass in each one of the species.

CONCLUSIONS

Fractal volumes of drug distribution scale proportionally to mass. This confirms the theoretically expected relationship between volume and mass in mammalian species.

Can absolute oral bioavailability in humans be predicted from animals? A comparison of allometry and different indirect methods

The objective of this study was to predict absolute bioavailability in humans from animal data using interspecies scaling as well as indirect approaches. Five different methods were used to predict absolute bioavailability in humans: (i) absolute bioavailability vs body weight (allometric approach); (ii) F = CL(IV)/CL(oral); (iii) F = 1-[CL(IV)/Q]; (iv) F = 1-[CL(oral)/Q]; and (v) F = Q/[Q + CL(oral)]. Methods II-V are indirect approaches, where predicted i.v. or oral clearance and hepatic blood flow (Q) (1500 ml/min) were used to predict absolute bioavailability in humans. Fifteen drugs were tested and the results of this study indicate that all five approaches predict absolute bioavailability with different degrees of accuracy, and are therefore unreliable for the accurate prediction of absolute bioavailability in humans from animal data. In conclusion, although the above-mentioned approaches do not accurately predict absolute bioavailability, a rough estimate of absolute bioavailability is possible using these approaches.

Prediction of clearance, volume of distribution and half-life by allometric scaling and by use of plasma concentrations predicted from pharmacokinetic constants: a comparative study

Pharmacokinetic parameters (clearance, CL, volume of distribution in the central compartment, VdC, and elimination half-life, t1/2beta) predicted by an empirical allometric approach have been compared with parameters predicted from plasma concentrations calculated by use of the pharmacokinetic constants A, B, alpha and beta, where A and B are the intercepts on the Y axis of the plot of plasma concentration against time and alpha and beta are the rate constants, both pairs of constants being for the distribution and elimination phases, respectively. The pharmacokinetic parameters of cefpiramide, actisomide, troglitazone, procaterol, moxalactam and ciprofloxacin were scaled from animal data obtained from the literature. Three methods were used to generate plots for the prediction of clearance in man: dependence of clearance on body weight (simple allometric equation); dependence of the product of clearance and maximum life-span potential (MLP) on body weight; and dependence of the product of clearance and brain weight on body weight. Plasma concentrations of the drugs were predicted in man by use of A, B, alpha and beta obtained from animal data. The predicted plasma concentrations were then used to calculate CL, VdC and t1/2beta. The pharmacokinetic parameters predicted by use of both approaches were compared with measured values. The results indicate that simple allometry did not predict clearance satisfactorily for actisomide, troglitazone, procaterol and ciprofloxacin. Use of MLP or the product of clearance and brain weight improved the prediction of clearance for these four drugs. Except for troglitazone, VdC and t1/2beta predicted for man by use of the allometric approach were comparable with measured values for the drugs studied. CL, VdC and t1/2beta predicted by use of pharmacokinetic constants were comparable with values predicted by simple allometry. Thus, if simple allometry failed to predict clearance of a drug, so did the pharmacokinetic constant approach (except for actisomide). The results of this study indicate that caution should be employed in interpreting plasma concentrations predicted for a drug in man by use of pharmacokinetic constants obtained in animals.

Interspecies scaling: predicting clearance of drugs in humans. Three different approaches

1. The interspecies scaling approach to predict clearance in humans from animal data was tested for a wide variety of drugs. 2. Three different methods were utilized to generate plots to scale-up the clearance values: (i) method I, clearance versus body weight (simple allometric equation); (ii) method II, product of clearance and maximum life-span potential; (iii) method III, product of clearance and brain weight versus body weight. 3. The circumstances under which the three methods can be applied to predict clearance in humans were evaluated. 4. If the exponent lies between 0.55 to 0.7 then method I predicts clearance reasonably well. 5. If the exponent lies between 0.71 to 1.0 clearance can be predicted reasonably well by method II. 6. If the exponent is > 1.0 clearance can be predicted using method III.

Importance of pharmacokinetic and physicochemical data in the discovery and development of novel anti-arrhythmic drugs

1. The importance of pharmacokinetics and physicochemical data in the discovery and development of a new mono-cationic antiarrhythmic agent, bidisomide (pKa 9.3), structurally related to the di-cationic anti-arrhythmic disobutamide (pKa of 8.6 and 10.2) and a mono-cationic drug disopyramide (pKa 10.4), is described. 2. In man, the di-cationic disobutamide was slowly eliminated with a mean terminal phase half-life of 54 +/- 18 h, a value > 7 times longer than disopyramide. The long terminal phase half-life of disobutamide is attributed to high accumulation of the drug in the tissues, a phenomenon attributed to the di-cationic nature. 3. Structural modification of disobutamide resulted in the mono-cationic agent bidisomide, designed to minimize drug accumulation in the tissues. Human studies with bidisomide confirmed that the terminal phase elimination of this drug was much faster than that of disobutamide, with a half-life of about 11h. The absolute bioavailability of bidisomide was 45-62% which is lower than that of disopyramide (60-90%). 4. Unlike disopyramide, absorption of bidisomide was complex, characterized by a lag period (0.75-1.5 h) before absorption, followed by occurrence of two peaks in the plasma concentration-time curves. 5. The characteristic double peaks found with bidisomide was attributed to two rapid absorption sites of the drug in the gastrointestinal tract.

Absorption and disposition of a new antiarrhythmic agent bidisomide in man

Absorption and disposition of bidisomide were studied in 12 healthy male subjects after a 20-min iv (1 mg/kg; N = 6) infusion and oral (2 mg/kg; N = 6) administration of the 14C-labeled drug. The oral absorption profile of unlabeled bidisomide was also studied after administration of a solution by a nasoenteric tube to different sites of the gastrointestinal tract (stomach, duodenum, jejunum, and ileum). The systemic availability was 61%. Absorption was slow initially and then rapid, achieving peak plasma concentrations between 2 and 4 hr. Less than complete systemic availability was attributed to incomplete absorption rather than first-pass metabolism. When the drug solution was delivered directly to the stomach, two distinct peak plasma levels were found. This was attributed to the more rapid absorption of bidisomide in the duodenum and ileum (and/or possibly colon). Following an iv dose, plasma levels of the drug declined with mean half-lives of 0.11, 2.0, and 12 hr for alpha, beta, and gamma phases, respectively, and a plasma clearance of 380 mL/min. The percentages of the dose recovered as bidisomide in urine and feces were 19 +/- 1 and 29 +/- 4 for the iv dose and 9.1 +/- 0.9 and 48 +/- 5 for the oral dose. Bidisomide did not exhibit substantial enantioselective pharmacokinetics in plasma regardless of the route of administration. The mean urinary excretion of the (-) enantiomer was, however, slightly higher than that of the (+) enantiomer, with (-)/(+) enantiomeric ratios of 1.2 and 1.3 after iv and oral administration, respectively. The enantiomeric ratio of bidisomide recovered in the feces was approximately 1.