Pharmacokinetic studies validation

Liu, A. et al.. Validated LC/MS/MS assay for curcumin and tetrahydrocurcumin in rat plasma and application to pharmacokinetic study of phospholipid complex of curcumin, J. Pharm. Biomed. Anal, 40, 720, 2006. 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

Amlodipine — Ma et al.50 developed and validated a UPLC/MS/MS method for a pharmacokinetic study of amlodipine in human plasma after oral administration. Nimodipine 50 fig/mL in a mixture of methanol and water (50 50 v/v) served as the IS. Standard solutions of amlodipine were also prepared in a mixture of methanol and water (50 50 v/v). 

In addition, compound 15 also had good metabolic stability in human liver microsome in vitro assay (hLM ti/2 = 39min) and in rat in vivo pharmacokinetic studies (ty2 = 3.3 h, po), with a rat oral bioavailability of 15%, showing a significant improvement in these PK parameters over the lead compound 1. The observed improvement in PK during the optimization was another validation of the strategy discussed above. This part of the optimization process is summarized in Scheme 19.2. 

Analytical data generated in a testing laboratory are generally used for development, release, stability, or pharmacokinetic studies. Regardless of what the data are required for, the analytical method must be able to provide reliable data. Method validation (Chapter 7) is the demonstration that an analytical procedure is suitable for its intended use. During the validation, data are collected to show that the method meets requirements for accuracy, precision, specificity, detection limit, quantitation limit, linearity, range, and robustness. These characteristics are those recommended by the ICH and will be discussed first. 

Validation of the Model. The Corley model was validated using chloroform data sets from oral (Brown et al. 1974a) and intraperitoneal (Ilett et al. 1973) routes of administration and from human pharmacokinetic studies (Fry et al. 1972). Metabolic rate constants obtained from the gas-uptake experiments were validated by modeling the disposition of radiolabeled chloroform in mice and rats following inhalation of chloroform at much lower doses. For the oral data set, the model accurately predicted the total amounts of chloroform metabolized for both rats and mice. 

Interroute Extrapolation. The Corley model used three routes of administration, intraperitoneal, oral and inhalation, in rats and mice to describe the disposition of chloroform. This data was validated for humans by comparing the model output using the animal data with actual human data from human oral chloroform pharmacokinetic studies. Using the human pharmacokinetic constants from the in vitro studies conducted by Corley, the model made adequate predictions of the amount of chloroform metabolized and exhaled in both males and females. 

In a pharmacokinetic study [49], this and related aspects of doxycycline were studied in man. Although the degree of serum protein binding as estimated by these workers was lower than in the report [41] discussed above, the differences seem inadequate to call in question the validity of their conclusions in addition, serum levels and protein binding data are not, of themselves, reliable indicators of therapeutic potential. 

During the 1990 Washington Conference on Analytical Methods Validation Bioavailability, Bioequivalence and Pharmacokinetic Studies [1], parameters that should be used for method validation were defined. The final report of this conference is considered the most comprehensive document on the validation of bioanalytical methods. Many multinational pharmaceutical companies and contract research organizations contributed to its final draft. This scientific meeting was sponsored by the American Association of Pharmaceutical Scientists (AAPS), the Association of Official Analytical Chemists (AOAC), and the U.S. Food and Drug Administration (FDA). The conference report has been used as a reference by bioanalytical laboratories and regulatory agencies worldwide. 

V. Borek-Dohalsky, J. Huclova, B. Barrett, B. Nemec, I. Ulc, I. Jelinek, Validated HPLC-MS-MS method for simultaneous determination of atorvastatin and 2-hydroxyatorvas-tatin in human plasma-pharmacokinetic study, Anal. Bioanal. Chem. 386 (2006) 275-285. 

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed [33] and validated for the determination of donepezil in human plasma samples. Diphenhydramine was used as the IS. The collision-induced transition m/z 380 > 91 was used to analyze donepezil in selected reaction monitoring mode. The signal intensity of the m/z 380 —> 91 transition was found to relate linearly with donepezil concentrations in plasma from 0.1 to 20.0 ng/ml. The lower limit of quantification of the LC/MS/MS method was 0.1 ng/ml. The intra- and inter-day precisions were below 10.2% and the accuracy was between 2.3% and +2.8%. The validated LC/MS/MS method was applied to a pharmacokinetic study in which healthy Chinese volunteers each received a single oral dose of 5 mg donepezil hydrochloride. The non-compartmental pharmacokinetic model was used to fit the donepezil plasma concentration-time curve. Maximum plasma concentration was... 

HPLC with column switching and mass spectrometry was applied to the online determination and resolution of the enantiomers of donepezil HC1 in plasma [38]. This system employs two avidin columns and fast atom bombardment-mass spectrometry (FAB-MS). A plasma sample was injected directly into an avidin trapping column (10 mm x 4.0 mm i.d.). The plasma protein was washed out from the trapping column immediately while donepezil HC1 was retained. After the column-switching procedure, donepezil HC1 was separated enantioselectivity in an avidin analytical column. The separated donepezil HC1 enantiomers were specifically detected by FAB-MS without interference from metabolites of donepezil HC1 and plasma constituents. The limit of quantification for each enantiomer of donepezil HC1 in plasma was 1.0 ng/ml and the intra-and inter-assay RSDs for the method were less than 5.2%. The assay was validated for enantioselective pharmacokinetic studies in the dog. 

Pharmacotoxic and pharmacokinetic studies carried out for the new antitumor drug Aviscumine (rViscumin) were supported by a robust quantitative IPCR assay developed by Adler et al. [66, 85], The potency of this protein-based drug, derived from recombinant mistletoe lectine, required initial doses well below the quantification range accessible by conventional ELISA. An IPCR assay was adapted and validated for the quantification of rViscumin in standardized human serum [66, 85, 86] and subsequently... 

Shah VP, Midha KK, Dighe SV, et ah Analytical methods validation bioavailability, bioequivalence, and pharmacokinetic studies./. Pharm. Sci. (1992) 81 309-312. 

Furlong MT et al (2012) A validated LC-MS/MS assay for the simultaneous determination of the anti-leukemic agent dasatinib and two pharmacologically active metabolites in human plasma application to a clinical pharmacokinetic study. J Pharm Biomed Anal 58 ... 

One key issue is the requirement for animal testing. The report and recommendations of the European Centre for the Validation of Alternative Methods (ECVAM) workshop (Leahy et al., 1997) clearly state that a major priority is to reduce the number of animals used in pharmacokinetic studies in drug development. As much information as possible should be obtained from alternative sources, such as computer modeling or using data already generated for similar compounds. 

Pharmacokinetic studies are often used to establish the extent of exposure to a biopharmaceutical in a preclinical study. This information not only validates dosing but also provides a means of extrapolating exposure across species. It... 

Assays used for bioanalytical measurements were validated, as the complete evaluation, assessment, and reporting of these clinical pharmacokinetic studies followed international and scientific quality standards. 

Successful completion of the above experiments will characterize methods for use in evaluating a lead candidate in animal models. If a candidate is selected for further development, the method will need to be validated (3,4) for each matrix and for each species before being used to support definitive toxicology, drug metabolism, and pharmacokinetic studies. 

VP Shah. Analytical methods validation Bioavailability, bioequivalence and pharmacokinetic studies. Pharm Res 9(4) 588-592, 1992. 

Morrison, J.G., White, P., McDougall, S., Firth, J.W., Woolfrey, S.G., Graham, M.A., Greenslade, D. Validation of a highly sensitive ICP-MS method for the determination of platinum in biofluids application to clinical pharmacokinetic studies with oxaliplatin. J. Pharm. Biomed. Anal. 24, 1-10 (2000)... 

Findlay, J.W.A. Validation in practice-experience with immunoassay. In Bio-International 2. Bioavailability, Bioequivalence and Pharmacokinetic Studies Blume, H.H., Midha, K.K., Eds. Medpharm Scientific Publishers Stuttgart, 1995 361-370. 

Cook, C.E. McDowall, R.D. Pittman, K.A. Spector, S. Analytical methods validation, bioavailability, bioequivalence and pharmacokinetic studies. Pharm. Res. 1992, 9 (4), 588-592. 

Standard Two-Stage Method. Population characteristics of each parameter are estimated as the empirical mean (arithmetic or geometric) and variance of the individual estimates pharmacokinetic parameters derived from experimental pharmacokinetic studies. ° The advantage of the STS approach is its simplicity, but the validity of its results should not be overemphasized. It has been shown from simulation studies that the STS approach tends to overestimate parameter dispersion. ... 

The validated bioanalysis of rosuvastatin in human plasma by automated SPE in 96-well format with Oasis HLB material and positive-ion LC-ESI-MS-MS was reported using a [DJ-ILIS [54]. The stability of rosuvastatin and its potential conversion into the lactone due to sample pretreatment was thoroughly investigated. The method was applied in pharmacokinetic studies during clinical trials. A similar method was applied by the same group in the bioanalysis of the /V-desmethyl metabolite of rosuvastatin [55]. 

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