A simple pharmacokinetics subroutine for modeling double peak phenomenon

Pharmacokinetics and tolerability of single-dose enteral cannabidiol and cannabidiolic acid rich hemp in horses (Equus caballus)

The pharmacokinetics and tolerability of cannabinoids and their metabolites were determined in eight horses after enteral administration of a commercial CBD/CBDA-rich hemp oil product. Each horse was administered 2 mg/kg or 8 mg/kg CBD/CBDA or no treatment in a randomized cross-over design. Serial serum samples collected over 48 h were analyzed by high performance liquid chromatography with tandem mass spectrometry. Plasma chemistry analysis was performed at 0 h and 24 h. Vital parameters, pedometry, and blinded mentation and gait evaluations were recorded at intervals up to 24 h. Manure production and gastrointestinal transit time were tracked for 48 h after oil administration. The median maximal concentration of CBD and CBDA were 5.2 and 36.95 ng/mL in the 2 mg/kg group, respectively; and 40.35 and 353.56 ng/mL in the 8 mg/kg group. The median half-life of elimination was not calculated for the 2 mg/kg CBD treatment due to lack of time points above the lower quantifiable limit beyond the Cmax while it was 7.75 h in the 8 mg/kg group. CBDA absorption was biphasic. Pharmacokinetic parameters for tetrahydrocannabinol, tetrahydrocannabinolic acid, cannabigerolic acid, and 7-carboxy cannabidiol are also reported. No significant differences in any of the measured tolerability parameters were demonstrated between treatment groups. Single-dose enteral administration of CBD/CBDA-rich hemp extract up to 8 mg/kg does not appear to produce neurologic, behavioral, or gastrointestinal effects in horses.

Metabolic profiling and pharmacokinetic studies of Baihu-Guizhi decoction in rats by UFLC-Q-TOF-MS/MS and UHPLC-Q-TRAP-MS/MS

Background

Baihu-Guizhi decoction (BHGZD) is a well-documented traditional Chinese Medicine (TCM) prescription that has been extensively applied to treating rheumatoid arthritis. Despite of its beneficial outcomes, the chemical constituents of BHGZD have not been fully portrayed and the in vivo absorption, distribution, metabolism, and excretion (ADME) patterns of absorbed components have never been described.

Methods

Characterization of absorbed components and in vivo biotransformation profiling of these feature compounds were based on the ultra-fast liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UFLC-Q-TOF-MS/MS). Furthermore, the ultra-high-performance liquid chromatography tandem ion trap quadrupole mass spectrometry (UHPLC-Q-TRAP-MS/MS) system were performed to investigate the pharmacokinetics of active ingredients from BHGZD.

Results

In this study, we have identified and tentatively characterized 18 feature absorbed prototype and 15 metabolites of BHGZD in rat serum and the in vivo transformation pathways of these absorbed constituents were proposed. Besides, we have established novel quantitative methodology of five crucial components of BHGZD and have monitored the pharmacokinetic behaviors of these constituents spontaneously in rat serum after BHGZD gavage. After rats received two ways of BHGZD gavage, the pharmacokinetic behaviors of each compound exhibited relatively similar behaviors, as evidenced by similar curve track as well as relatively close time to reach maximum concentration (Tmax) and half washout time (T1/2). Whereas the maximum plasma concentration (Cmax) and area under the plasma concentration–time curve (AUC) values of five analytes with multiple dosage were a bit higher than single dosage.

Conclusion

This study added knowledge into the material basis and bio-transformation patterns of BHGZD in vivo, which would be of great value for exploring pharmacological effects and mechanism of BHGZD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-022-00665-w.

pH-Responsive Emulsions with β-Cyclodextrin/Vitamin E Assembled Shells for Controlled Delivery of Polyunsaturated Fatty Acids

Lipid-based delivery systems (LBDSs) are widely applied in pharmaceuticals and health care because of the increased bioavailability of lipophilic components when they are coadministered with high-fat meals. However, how to accurately control their in vivo release and stability is still challenging. Here, after introducing the simple esterification and coprecipitation, we created the dual-functional composite ODS-β-CD-VE by the coassembly of β-cyclodextrin (β-CD), octadecenyl succinic anhydride (ODSA), and vitamin E (VE). The resulting dual-functional particle presented a uniform sheetlike shape and nanometer size. In addition, its chemical structure was clarified in detail via nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Benefiting from the antioxygenation of VE, lipid oxidation in the ODS-β-CD-VE-stabilized Pickering emulsion was effectively inhibited. Meanwhile, pH-induced protonation/deprotonation of carboxyl groups guaranteed that the emulsions kept steady at pH ≤4 but were unsteady under neutral conditions. In this way, the lipids contained in the emulsion were protected from gastric juice and then digested and accurately released as n-3 polyunsaturated fatty acids (PUFA) in the simulated intestine environment. This strategy sheds some light on the rational and efficient construction of LBDSs for nutrient supplements and even pharmaceuticals in a living digestive tract.

Sex-, feeding-, and circadian time-dependency of P-glycoprotein expression and activity - implications for mechanistic pharmacokinetics modeling

P-glycoprotein (P-gp) largely influences the pharmacokinetics (PK) and toxicities of xenobiotics in a patient-specific manner so that personalized drug scheduling may lead to significant patient's benefit. This systems pharmacology study investigated P-gp activity in mice according to organ, sex, feeding status, and circadian time. Sex-specific circadian changes were found in P-gp ileum mRNA and protein levels, circadian amplitudes being larger in females as compared to males. Plasma, ileum and liver concentrations of talinolol, a pure P-gp substrate, significantly differed according to sex, feeding and circadian timing. A physiologically-based PK model was designed to recapitulate these datasets. Estimated mesors (rhythm-adjusted mean) of ileum and hepatic P-gp activity were higher in males as compared to females. Circadian amplitudes were consistently higher in females and circadian maxima varied by up to 10 h with respect to sex. Fasting increased P-gp activity mesor and dampened its rhythm. Ex-vivo bioluminescence recordings of ileum mucosae from transgenic mice revealed endogenous circadian rhythms of P-gp protein expression with a shorter period, larger amplitude, and phase delay in females as compared to males. Importantly, this study provided model structure and parameter estimates to refine PK models of any P-gp substrate to account for sex, feeding and circadian rhythms.

Effects of SLC22A1 Polymorphisms on Metformin-Induced Reductions in Adiposity and Metformin Pharmacokinetics in Obese Children With Insulin Resistance

Steady-state population pharmacokinetics of a noncommercial immediate-release metformin (hydrochloride) drug product were characterized in 28 severely obese children with insulin resistance. The concentration-time profiles with double peaks were well described by a 1-compartment model with 2 absorption sites. Mean population apparent clearance (CL/F) was 68.1 L/h, and mean apparent volume of distribution (V/F) was 28.8 L. Body weight was a covariate of CL/F and V/F. Estimated glomerular filtration rate was a significant covariate of CL/F (P < .001). SLC22A1 genotype did not significantly affect metformin pharmacokinetics. The response to 6 months of metformin treatment (HbA_1c , homeostasis model assessment for insulin resistance, fasting insulin, and glucose changes) did not differ between SLC22A1 wild-type subjects and carriers of presumably low-activity SLC22A1 alleles. However, SLC22A1 variant carriers had smaller reductions in percentage of total trunk fat after metformin therapy, although the percentage reduction in trunk fat was small. The median % change in trunk fat was -2.20% (-9.00% to 0.900%) and -1.20% (-2.40% to 7.30%) for the SLC22A1 wild-type subjects and variant carriers, respectively. Future study is needed to evaluate the effects of SLC22A1 polymorphisms on metformin-mediated weight reduction in obese children.

Role of enterohepatic recirculation in drug disposition: cooperation and complications

Enterohepatic recirculation (EHC) concerns many physiological processes and notably affects pharmacokinetic parameters such as plasma half-life and AUC as well as estimates of bioavailability of drugs. Also, EHC plays a detrimental role as the compounds/drugs are allowed to recycle. An in-depth comprehension of this phenomenon and its consequences on the pharmacological effects of affected drugs is important and decisive in the design and development of new candidate drugs. EHC of a compound/drug occurs by biliary excretion and intestinal reabsorption, sometimes with hepatic conjugation and intestinal deconjugation. EHC leads to prolonged elimination half-life of the drugs, altered pharmacokinetics and pharmacodynamics. Study of the EHC of any drug is complicated due to unavailability of the apposite model, sophisticated procedures and ethical concerns. Different in vitro and in vivo methods for studies in experimental animals and humans have been devised, each having its own merits and demerits. Involvement of the different transporters in biliary excretion, intra- and inter-species, pathological and biochemical variabilities obscure the study of the phenomenon. Modeling of drugs undergoing EHC has always been intricate and exigent models have been exploited to interpret the pharmacokinetic profiles of drugs witnessing multiple peaks due to EHC. Here, we critically appraise the mechanisms of bile formation, factors affecting biliary drug elimination, methods to estimate biliary excretion of drugs, EHC, multiple peak phenomenon and its modeling.

Empirical and semi-mechanistic modelling of double-peaked pharmacokinetic profile phenomenon due to gastric emptying

Models have been developed to explain double-peaked plasma concentration-time profiles using mechanisms such as variable absorption and enterohepatic recirculation. Interruption of gastric emptying has also been shown to produce double-peaks, and this work proposes models for analysis of such data. In the presence of levodopa, gastric emptying is interrupted at times associated with double-peaks in pharmacokinetic profiles. Data from a simultaneous scintigraphy and paracetamol absorption study with levodopa was obtained, and models with compartments for stomach, intestine, central and peripheral tissue were developed to describe levodopa and paracetamol pharmacokinetics, including the double-peak phenomenon. The empirical model uses two gastric emptying parameter rates which are applied over separate time periods to describe the varying gastric emptying rate. The semi-mechanistic model uses a feedback mechanism acting via an effect compartment to link the plasma concentration of levodopa to the rate of gastric emptying, allowing levodopa pharmacokinetics to vary the rate of gastric emptying and give rise to a multiple-peaked plasma pharmacokinetic profile. The models were applied to plasma levodopa and paracetamol pharmacokinetic data with and without simultaneous analysis of scintigraphy data, in both cases giving a good fit and in the absence of scintigraphy data adequately predicting the stomach profile. For the semi-mechanistic model, the first-order constant governing gastric emptying was shown to switch between fast and slow values at a critical levodopa effect compartment concentration. New models have thus been proposed for analysis of plasma concentration profiles that exhibit double-peak phenomenon and applied successfully to levodopa data.

C (max) and t (max) verification using Fibonacci sequence and absorption rate

The aim of this study was to verify the values of maximal observed concentration (C max,obs) and the time, at which maximum concentration is observed (t max,obs) using the analysis of the absorption rate constant (k ab). It focused on the changes in concentration over time (C-T) for drugs, for which several peaks of concentration occur. In addition, the attempt was made to use Fibonacci sequence to facilitate the visual analysis of the dynamics in changes of concentration on C-T graphs. The analyses were conducted with the use of three hypothetical data groups (groups I, II and III), which had distinct C-T profiles, and with the in vivo data form healthy subjects (n = 10) taking part in a bioequivalence study, who was given a single oral dose of topiramate (100 mg). The comparison of hypothetical and real in vivo data demonstrated that for the C-T curves, in which there are several peaks of concentration C max,obs and t max,obs values can easily be miscalculated when the increase in concentration is not properly related to the appropriate absorption phase (63.2, 87.50, 96.88 %). It was also demonstrated that the data transformation with the use of Fibonacci sequence exposes slight differences in the observed concentration values in a semi-logarithmic scale. The results of this study show that in case of C-T curves with several peaks of concentration, the verification of C max and t max data obtained taking into account different absorption phases enables more precise evaluation of these parameters.

Pharmacokinetics of mequindox and its metabolites in rats after intravenous and oral administration

Pharmacokinetics of mequindox (MEQ) and its metabolites were determined in rats after intravenous (i.v.) and oral (p.o.) administration of MEQ at a single dose of 10 mg kg(-1) bodyweight. After both administrations, MEQ and five of its metabolites were quantified, except M4, whereas M1 and M2 were the predominant ones. The areas under the concentration-time curves (h ng mL(-1)) of MEQ, M1, M2, M3, M5 and M10 after i.v. administration were 7559±495, 6354±2761, 5586±2337, 1034±160, 2370±791 and 1813±622, respectively, whereas after p.o. administration, remained as 2809±40, 4361±3544, 4351±1046, 1444±814, 3864±305 and 1213±569, respectively. The elimination half-lives (h) of these compounds after i.v. administration were 3.48±0.80, 4.20±0.76, 6.25±2.41, 4.77±1.54, 4.69±1.62 and 16.89±5.15, respectively, and were 3.21±0.40, 3.66±1.06, 4.20±1.03, 8.91±5.99, 4.20±2.02 and 20.84±10.85 after p.o. administration, respectively. After p.o. administration, the bioavailability of MEQ was 37.16%. The results showed that MEQ was extensively metabolized in rats and rapidly absorbed after p.o. administration.

Modelling the Double Peak Phenomenon in pharmacokinetics

Two methods of modelling the Double Peak Phenomenon in pharmacokinetics are described; both are based on compartmental models. The first method assumes that the absorption of the drug from the gut to the systemic plasma varies with the location of the drug in the gut, with negligible absorption through the jejunum. It has the advantage of clear physiological interpretation, but there are a comparatively large number of parameters to be estimated. The second method assumes simultaneous input via two parallel pathways, and has been developed with the aim of reducing the number of parameters in the model. However, this approach lacks the direct relationship to physiology. The two methods are used to model two data sets provided by AstraZeneca and a further data set from the literature, describing the pharmacokinetics of veralipride. For all three data sets, the measurement is of concentration of drug in the systemic plasma following oral administration in solution form.

Effect of centchroman coadministration on the pharmacokinetics of metformin in rats

Objectives:

To study the effect of centchroman, a non-steroidal oral contraceptive, coadministration on the pharmacokinetics of metformin in rats.

Materials and Methods:

The pharmacokinetic interaction of metformin was studied in normal Sprague-Dawley female rats with and without centchroman coadministration. Blood samples were analyzed using a validated high-performance liquid chromatography method to generate the pharmacokinetic profile of metformin. The C_max and t_max were directly read from the concentration–time data. Other pharmacokinetic parameters were estimated using non-compartmental analyses.

Results:

Metformin was monitored up to 10 h, and it exhibited a double-peak phenomenon. The C_{max 1}, 2.62 ± 0.32 μg/ml, and C_{max 2,} 2.96 ± 0.65 μg/ml, occurred after 0.75 and 3 h post-dose, respectively. The mean residence time (MRT), AUC_{0-4 h} and volume of distribution (Vd/F) were 4.20 ± 0.30 h, 8.53 ± 1.89 μg.h/ml and 14.24 ± 5.42 L/kg, respectively. Following centchroman coadministration, metformin showed significantly (P < 0.05) higher C_max (C_{max 1,} 3.96 ± 0.55 μg/ml and C_{max 2,} 5.21 ± 0.59 μg/ml), AUC_{0-4 h} (12.28 ± 0.73 μg.h/ml) and Vd/F (18.29 ± 1.19 L/kg), but lower MRT (3.19 ± 0.36 h) than the values obtained after metformin dosing alone. However, AUC_0-t (17.74 ± 5.58 μg.h/ml) and clearance (3.76 ± 0.80 L/h/kg) remained unchanged.

Conclusions:

The results indicate that centchroman coadministration increases the rate but not the extent of absorption of metformin in rats. However, it does not seem to alter the pharmacokinetics of metformin to clinically significant levels.

Physiologically motivated time-delay model to account for mechanisms underlying enterohepatic circulation of piroxicam in human beings

The study was conducted to formulate a physiologically motivated time-delay (PM TD) mathematical model for human beings, which incorporates disintegration of a drug formulation, dissolution, discontinuous gastric emptying and enterohepatic circulation (EHC) of a drug. Piroxicam, administered to 24 European, healthy individuals in 20 mg capsules Feldene Pfizer, was used as a model drug. Plasma was analysed for piroxicam by a validated high-performance liquid chromatography method. The PM TD mathematical model was developed using measured plasma piroxicam concentration-time profiles of the individuals and tools of a computationally efficient mathematical analysis and modeling, based on the theory of linear dynamic systems. The constructed model was capable of (i) quantifying different fractions of the piroxicam dose sequentially disposable for absorption and (ii) estimating time delays between time when the piroxicam dose reaches stomach and time when individual of fractions of the piroxicam dose is disposable for absorption. The model verification was performed through a formal proof, based on comparisons of observed and model-predicted plasma piroxicam concentration-time profiles. The model verification showed an adequate model performance and agreement between the compared profiles. Accordingly, it confirmed that the developed model was an appropriate representative of the piroxicam fate in the individuals enrolled. The presented model provides valuable information on factors that control dynamic mechanisms of EHC, that is, information unobtainable with the models proposed for the EHC analysis previously.

Preclinical factors affecting the pharmacokinetic behaviour of tanshinone IIA, an investigational new drug isolated from Salvia miltiorrhiza for the treatment of ischaemic heart diseases

Tanshinone IIA (TSIIA) is a major active triterpenoid isolated from Salvia miltiorrhiza. The purposes of this study were to investigate various preclinical factors that determined the pharmacokinetics of TSIIA. After oral dosing at 6.7, 20, and 60 mg kg(-1), TSIIA was detected mainly as glucuronidated conjugate (TSIIAG) with only small amounts of the unchanged in the plasma. TSIIA was predominantly excreted into the bile and faeces as TSIIAG, and urine to a minor extent. The C(max) and AUC(0-)(t) of TSIIAG after i.p. administration were significantly lower than those after intragastric administration. The plasma concentration-time profiles of TSIIA following oral dosing of TSIIA showed multiple peaks. The C(max) and AUC(0-)(t) of TSIIA and its glucuronides in rats with intact bile duct were significantly lower than those of rats with bile duct cannulation. Studies from the linked-rat model and intraduodenal injection of bile containing TSIIA and its metabolites indicate that TSIIA glucuronides underwent hydrolysis and the aglycone was reabsorbed from the gut and excreted into the bile as conjugates. TSIIA had a wide tissue distribution, with a very high accumulation in the lung, but very limited penetration into the brain and testes. TSIIA was metabolized by rat CYP2C, 3A and 2D, as ticlopidine, ketoconazole and quinidine all inhibited TSIIA metabolism in rat liver microsomes. Taken collectively, these findings indicate that multiple factors play important roles in determining the pharmacokinetics of TSIIA.