Protein binding of indomethacin in human cerebrospinal fluid

Pantothenate Kinase Activation Restores Brain Coenzyme A in a Mouse Model of Pantothenate Kinase-Associated Neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) is characterized by a motor disorder with combinations of dystonia, parkinsonism, and spasticity, leading to premature death. PKAN is caused by mutations in the PANK2 gene that result in loss or reduction of PANK2 protein function. PANK2 is one of three kinases that initiate and regulate coenzyme A biosynthesis from vitamin B5, and the ability of BBP-671, an allosteric activator of pantothenate kinases, to enter the brain and elevate coenzyme A was investigated. The metabolic stability, protein binding, and membrane permeability of BBP-671 all suggest that it has the physical properties required to cross the blood-brain barrier. BBP-671 was detected in plasma, liver, cerebrospinal fluid, and brain following oral administration in rodents, demonstrating the ability of BBP-671 to penetrate the brain. The pharmacokinetic and pharmacodynamic properties of orally administered BBP-671 evaluated in cannulated rats showed that coenzyme A (CoA) concentrations were elevated in blood, liver, and brain. BBP-671 elevation of whole-blood acetyl-CoA served as a peripheral pharmacodynamic marker and provided a suitable method to assess target engagement. BBP-671 treatment elevated brain coenzyme A concentrations and improved movement and body weight in a PKAN mouse model. Thus, BBP-671 crosses the blood-brain barrier to correct the brain CoA deficiency in a PKAN mouse model, resulting in improved locomotion and survival and providing a preclinical foundation for the development of BBP-671 as a potential treatment of PKAN. SIGNIFICANCE STATEMENT: The blood-brain barrier represents a major hurdle for drugs targeting brain metabolism. This work describes the pharmacokinetic/pharmacodynamic properties of BBP-671, a pantothenate kinase activator. BBP-671 crosses the blood-brain barrier to correct the neuron-specific coenzyme A (CoA) deficiency and improve motor function in a mouse model of pantothenate kinase-associated neurodegeneration. The central role of CoA and acetyl-CoA in intermediary metabolism suggests that pantothenate kinase activators may be useful in modifying neurological metabolic disorders.

The Comparison of Plasma and Cerebrospinal Fluid R(-)- and S(+)-Flurbiprofen Concentration After Intravenous Injection of Flurbiprofen Axetil in Human Subjects

Background: Flurbiprofen axetil is a prodrug that releases the active substance through enzymatic removal of the ester moiety. It is formulated through encapsulation in a lipid microsphere carrier, and widely used to treat perioperative pain. Here, we studied the distribution of R (-)- and S (+)-flurbiprofen in human plasma and cerebrospinal fluid (CSF) after intravenous injection of flurbiprofen axetil. Methods: A total of 70 adult patients undergoing elective lower limb surgery under spinal anesthesia were given a single intravenous injection of 100-mg flurbiprofen axetil. The patients were randomly assigned to 10 groups for plasma and CSF sampling at 10 time points (5-50 min) after subarachnoid puncture and before actual spinal anesthesia. R (-)- and S (+)-flurbiprofen and CSF/plasma ratio were determined by liquid chromatography-tandem mass spectrometry. Results: R (-)-flurbiprofen concentration ranged from 2.01 to 10.9 μg/mL in plasma and 1.46-34.4 ng/mL in CSF. S (+)-flurbiprofen concentration ranged from 1.18 to 10.8 μg/mL in plasma and from 2.53 to 47 ng/mL in CSF. In comparison to S (+)-flurbiprofen, R (-)-flurbiprofen concentration was significantly higher in plasma at all time points (p < 0.05) except at 30 or 40 min, and lower in CSF at all time points (p < 0.05) except at 10, 15 and 40 min. Analysis after correcting drug concentration for body mass index also revealed higher plasma and lower CSF R (-)-flurbiprofen concentration. In comparison to S (+)-flurbiprofen, AUC_0-50 for R (-)-flurbiprofen was larger in plasma and smaller in CSF (p < 0.05 for both), and accordingly smaller CSF/plasma AUC_0-50 ratio (p < 0.05). There was a positive correlation between R (-)-flurbiprofen concentration and S (+)-flurbiprofen concentration in plasma (r = 0.725, p < 0.001) as well as in CSF (r = 0.718, p < 0.001), and a negative correlation between plasma and CSF concentration of S (+)-flurbiprofen (r = -0.250, p = 0.037), but not R (-)-flurbiprofen. Conclusion: Distribution of R (-)- and S (+)-flurbiprofen in plasma and CSF differed significantly. Penetration of R (-)-flurbiprofen into the CNS was lower than S (+)-flurbiprofen.

Optimization of 8-Hydroxyquinolines as Inhibitors of Catechol O-Methyltransferase

A series of 8-hydroxy quinolines were identified as potent inhibitors of catechol O-methyltransferase (COMT) with selectivity for the membrane-bound form of the enzyme. Small substituents at the 7-position of the quinoline were found to increase metabolic stability without sacrificing potency. Compounds with good pharmacokinetics and brain penetration were identified and demonstrated in vivo modulation of dopamine metabolites in the brain. An X-ray cocrystal structure of compound 21 in the S-COMT active site shows chelation of the active site magnesium similar to catechol-based inhibitors. These compounds should prove useful for treatment of many neurological and psychiatric conditions associated with compromised cortical dopamine signaling.

Plasma and cerebrospinal fluid pharmacokinetics of naproxen in children

The aim of this study was to characterize pediatric pharmacokinetics and central nervous system exposure of naproxen after oral administration. The pharmacokinetics of naproxen was studied in 53 healthy children aged 3 months to 12 years undergoing surgery with spinal anesthesia. Children received preoperatively a single dose of 10 mg/kg oral naproxen suspension. A single cerebrospinal fluid (CSF) sample (n = 52) was collected at the induction of anesthesia, and plasma samples (n = 270) were collected before, during, and after the operation (up to 51 hours after administration). A population pharmacokinetic model was built using the NONMEM software. Naproxen concentrations in plasma were well described by a 2-compartment model. The estimated oral clearance (CL/F) was 0.62 L/h when linearly scaled by weight to 70 kg. The apparent volume of distribution at steady state (Vss/F) was 12.5 L /70 kg. The findings are consistent with previously reported pharmacokinetic parameters for children older than 5 years. Naproxen permeated into the CSF and reached CSF concentrations that were 4 times higher than unbound plasma concentrations. Based on these data, weight can be used as a basis for naproxen dosing in children older than 3 months of age.

Plasma and cerebrospinal fluid pharmacokinetics of flurbiprofen in children

AIMS

This study was designed to characterize paediatric pharmacokinetics and central nervous system exposure of flurbiprofen.

METHODS

The pharmacokinetics of flurbiprofen were studied in 64 healthy children aged 3 months to 13 years, undergoing surgery with spinal anaesthesia. Children were administered preoperatively a single dose of flurbiprofen intravenously as prodrug (n= 27) or by mouth as syrup (n= 37). A single cerebrospinal fluid (CSF) sample (n= 60) was collected at the induction of anaesthesia, and plasma samples (n= 304) before, during and after the operation (up to 20 h after administration). A population pharmacokinetic model was built using the NONMEM software package.

RESULTS

Flurbiprofen concentrations in plasma were well described by a three compartment model. The apparent bioavailability of oral flurbiprofen syrup was 81%. The estimated clearance (CL) was 0.96l h(-1) 70 kg(-1) . Age did not affect the clearance after weight had been included as a covariate. The estimated volume of distribution at steady state (V(ss) ) was 8.1 l 70 kg(-1) . Flurbiprofen permeated into the CSF, reaching concentrations that were seven-fold higher compared with unbound plasma concentrations.

CONCLUSIONS

Flurbiprofen pharmacokinetics can be described using only weight as a covariate in children above 6months, while more research is needed in neonates and in younger infants.

Plasma and cerebrospinal fluid concentrations of indomethacin in children after intravenous administration

The objective of this study was to evaluate the cerebrospinal fluid (CSF) permeation of indomethacin in healthy children. The participants (n = 31, aged 4-144 months) received indomethacin (0.35 mg/kg) as a 10-minute intravenous infusion prior to surgery under spinal anaesthesia. A single CSF and plasma sample from each individual was collected 14 to 225 minutes after the infusion. Indomethacin concentrations were determined from the CSF, plasma, and protein-free plasma. Total plasma, protein-free plasma, and CSF concentrations of indomethacin ranged between 90 and 2200 ng/mL (median, 780 ng/mL), 0.3 and 0.8 ng/mL (median, 0.5 ng/mL), and 0.2 and 5.0 ng/mL (median, 1.4 ng/mL), respectively. The CSF to plasma concentration ratio remained less than 0.01. There was no correlation between the administration time and CSF concentrations. Eleven children developed 12 nonserious adverse effects, from which 5 were central nervous system (CNS) effects (agitation). In conclusion, indomethacin permeated into the CSF of children, which enables both desired and adverse CNS effects of indomethacin.

Stereoselective disposition of ibuprofen enantiomers in human cerebrospinal fluid

Since both (R)- and (S)-enantiomers of ibuprofen may act on the central nervous system, we investigated their plasma and cerebrospinal fluid (CSF) concentrations in 46 patients with nerve-root compression pain requiring a lumbar puncture. Each patient received an oral dose of 800 mg rac-ibuprofen. A single blood and CSF sample was drawn concomitantly from each patient at intervals between 30 min and 8 h after dosing. Both isomers peaked later in the CSF (3 h) than in the plasma (1.5 h). Their CSF concentrations became higher than their concurrent free plasma concentrations after 90 min. The estimated elimination half-lives of (R)- and (S)-ibuprofen were 1.7 h and 2.5 h in plasma and 3.9 h and 7.9 h in CSF, respectively. The AUCCSF/AUCplasma ratios (0, 8 h) were 0.009 and 0.015 for the (R)- and (S)-forms, respectively.

Binding sites of fluorescent probes on human serum albumin

Human serum albumin is known to have two major and selective drug binding sites, termed sites I and II. The fluorescent probes, dansylamide and dansylsarcosine selectively interact with sites I and II, respectively. However, the binding site of the fluorescent probe dansylglycine on human serum albumin is not clear from the literature. This study investigated whether dansylglycine interacts tightly with site I or II. Spectrofluorimetric titrations (quenching and complex) and circular dichroism measurements were performed to determine the binding characteristics of dansylglycine to human serum albumin. Modification in probe fluorescence was described by fluorescence titrations to be a result of competitive displacement by ligands. The pattern of displacement of this probe by several ligands whose primary binding sites are exactly known, enabled the identification of its specific binding site. The fluorescence of dansylglycine is only extensively changed when ligands of site II are added, suggesting that it strongly interacts with the benzodiazepine/indole binding site on human serum albumin.

Stereoselective binding of etodolac to human serum albumin

The protein binding of etodolac enantiomers was studied in vitro by equilibrium dialysis in human serum albumin (HSA) of various concentrations varying from 1 to 40 g/liter, by addition of each enantiomer at increasing concentrations. In the 1 g/liter solution, at the lowest drug levels, the (R)-form is more bound than its antipode, the contrary being observed at the highest drug levels. For higher albumin concentrations, S was bound in a larger extent than R. Using the displacement of specific markers of HSA sites I and II, studied by spectrofluorimetry, it was suggested that R and S are both bound to site I, while only S is strongly bound to site II.