Pharmacokinetics and synovial fluid concentrations of flurbiprofen enantiomers in horses: chiral inversion

Advancing ophthalmic delivery of flurbiprofen via synergistic chiral resolution and ion-pairing strategies

Flurbiprofen (FB), a nonsteroidal anti-inflammatory drug, is widely employed in treating ocular inflammation owing to its remarkable anti-inflammatory effects. However, the racemic nature of its commercially available formulation (Ocufen®) limits the full potential of its therapeutic activity, as the (S)-enantiomer is responsible for the desired anti-inflammatory effects. Additionally, the limited corneal permeability of FB significantly restricts its bioavailability. In this study, we successfully separated the chiral isomers of FB to obtain the highly active (S)-FB. Subsequently, utilizing ion-pairing technology, we coupled (S)-FB with various counter-ions, such as sodium, diethylamine, trimethamine (TMA), and l-arginine, to enhance its ocular bioavailability. A comprehensive evaluation encompassed balanced solubility, octanol-water partition coefficient, corneal permeability, ocular pharmacokinetics, tissue distribution, and in vivo ocular anti-inflammatory activity of each chiral isomer salt. Among the various formulations, S-FBTMA exhibited superior water solubility (about 1-12 mg/ml), lipid solubility (1< lg Pow < 3) and corneal permeability. In comparison to Ocufen®, S-FBTMA demonstrated significantly higher in vivo anti-inflammatory activity and lower ocular irritability (such as conjunctival congestion and tingling). The findings from this research highlight the potential of chiral separation and ion-pair enhanced permeation techniques in providing pharmaceutical enterprises focused on drug development with a valuable avenue for improving therapeutic outcomes.

Chiral liquid chromatography-mass spectrometry (LC-MS/MS) method development with β-cyclodextrin (β-CD) derivatized chiral stationary phase for the enhanced separation and determination of flurbiprofen enantiomers: application to a stereoselective pharmacokinetic study

Home-made chiral stationary phase for enhanced enantioselective separation and determination of flurbiprofen by liquid chromatography-mass spectrometry (LC-MS/MS) for the first time.

Analysis of loxoprofen in tablets, patches, and equine urine as tert-butyldimethylsilyl derivative by gas chromatography-mass spectrometry

Loxoprofen is a non-steroidal anti-inflammatory drug of the 2-arylpropionic acid type, which has used to treat musculoskeletal disorders in the horse racing industry. However, it has also used illicitly to mask clinical signs of inflammation and pain in racehorses. Thus, its accurate analysis has become an important issue in horse doping laboratories. In this study, an analytical method of loxoprofen was developed as tert-butyldimethylsilyl (TBDMS) derivative by gas chromatography-mass spectrometry (GC-MS). Characteristic fragment ions of [M-15], [M-57], and [M-139] permitted the accurate and selective detection of loxoprofen. Under optimal conditions, this method showed good linearity (r ≥ 0.999) in the range of 10-500 ng/mL, repeatability (% relative standard deviation = 5.6-8.5), and accuracy (% relative error = - 0.3-0.9) with a detection limit of 1.0 ng. When applied to the analysis of loxoprofen in tablet and patch products, loxoprofen was positively identified as TBDMS derivative by GC-MS. The present method provided rapid and accurate determination of loxoprofen in patch and tablet products. Levels of loxoprofen were highest in equine urine at 0.5 and 1 h after oral administration with single dose (3 mg/kg) to three horses, and then rapidly reduced to below the lower limit of quantification at 24 h. Therefore, the present method will be useful for the pharmacokinetic study and doping tests for loxoprofen and other similar acidic drugs in horses.

Chiral pharmacokinetics of zaltoprofen in rats by HPLC with solid-phase extraction

We investigated the pharmacokinetic profile of (R)- and (S)-zaltoprofen (ZPF) in rats using rapid and selective liquid chromatography with solid-phase extraction (SPE). The ZPF enantiomers were extracted from a small volume of plasma (0.2 mL) by means of SPE using cartridges and were analyzed on a Chiralcel OJ-H (4.6 mm × 150 mm, 5 μm) column with ultraviolet detection at 244 nm. The lower limit of quantification of the ZPF enantiomers in plasma was 0.1μg/mL. The validated method was successfully applied to chiral pharmacokinetic studies of oral administration of racemic ZPF to rats. (S)-ZPF showed significantly higher AUC, T(max), and C(max) and a longer half-life than (R)-ZPF, indicating higher bioavailability of the (S)-isomer. A total of 8 samples (about 12% of the total number of samples) were selected for incurred sample reanalysis (ISR). The % difference between the re-assay concentrations and the original concentrations were all less than 15% of their mean values and met the acceptance criteria for ISR.

Does stereochemistry influence transdermal permeation of flurbiprofen through the rat skin?

The possible enantioselectivity in the permeation of the chiral anti-inflammatory drug flurbiprofen across hairless rat skin was studied. The transdermal permeability of individual enantiomers from donor solution containing racemic flurbiprofen (0.1%) and pure enantiomers (0.05%) in isopropyl myristate solution was determined using side-by-side diffusion cells. The permeation profiles of enantiomers (R)- and (S)-flurbiprofen from donor solution containing racemic (RS)-flurbiprofen are comparable. When donor solution contained pure enantiomers, marked differences were observed between the permeation rates of (R)- and (S)-flurbiprofen. The steady-state flux and permeability coefficient were significantly higher for (R)-flurbiprofen in comparison with (S)-flurbiprofen (the flux ratio R/S = 2.04; p < 0.05).

Pharmacokinetic and bioequivalence comparison between orally disintegrating and conventional tablet formulations of flurbiprofen: a single-dose, randomized-sequence, open-label, two-period crossover study in healthy Chinese male volunteers

BACKGROUND

Flurbiprofen, an NSAID, is used for the treatment of inflammation and pain caused by rheumatoid arthritis and osteoarthritis as well as soft-tissue injuries. A new orally disintegrating tablet (ODT) of flurbiprofen has recently been developed; this study was conducted to provide support for this drug to obtain marketing authorization in China.

OBJECTIVE

The aim of the study was to compare the pharmacokinetic properties and bioequivalence of flurbiprofen 50-mg ODT (test) with a conventional flurbiprofen 50-mg tablet (reference) under fasting conditions in healthy volunteers.

METHODS

This was a single-dose, randomized-sequence, open-label, 2-period crossover study. Healthy, nonsmoking Chinese male volunteers were randomly assigned to receive 150 mg (administered as three 50-mg tablets) of either the test or reference formulation of flurbiprofen, followed by a 7-day washout period and administration of the alternate formulation. Study drugs were administered after a 12-hour overnight fast. Blood samples were collected before dosing and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours after dosing. Serum flurbiprofen concentrations were analyzed using a validated nonstereospecific liquid chromatography/tandem mass spectrometry method. Pharmacokinetic parameters, including C(max), T(max), t(1/2), AUC(0-24), and AUC(0-infinity), were calculated and analyzed statistically. C(max), AUC(0-24), and AUC(0-infinity) were used to test for bioequivalence after natural logarithm (ln)-transformation. Tolerability was evaluated throughout the study by clinical assessments, vital sign monitoring, physical examinations, 12-lead ECG, clinical laboratory tests, and questioning subjects about adverse events (AEs).

RESULTS

A total of 20 Chinese males (mean [SD] age, 21.4 [2.5] years [range, 19-28 years]; height, 174.4 [4.2] cm [range, 169-183 cm]; weight, 63.2 [5.1] kg [range, 56-78 kg]; body mass index, 20.8 [1.4] kg/m(2) [range, 19-24 kg/m(2)]) completed the study. No period or sequence effect was observed. The 90% CIs for the ln-transformed ratios of Cmax, AUC(0-24), and AUC(0-infinity) were 99.9% to 115.9%, 97.8% to 107.9%, and 100.3% to 110.9%, respectively, meeting the predetermined criteria for bioequivalence. Two subjects (10.0%) experienced 1 of 2 mild AEs (increase in total bilirubin and dizziness), which were not considered to be associated with study drug administration.

CONCLUSIONS

This single-dose 150-mg (three 50-mg tablets) study of each formulation of flurbiprofen found that the test and reference products met the regulatory criteria for bioequivalence in these fasting healthy Chinese male volunteers. Both formulations were generally well tolerated. State Food and Drug Administration of China study registration number: 2005L04356.

Drug disposition in three dimensions: an update on stereoselectivity in pharmacokinetics

Many marketed drugs are chiral and are administered as the racemate, a 50:50 combination of two enantiomers. Pharmacodynamic and pharmacokinetic differences between enantiomers are well documented. Because of enantioselectivity in pharmacokinetics, results of in vitro pharmacodynamic studies involving enantiomers may differ from those in vivo where pharmacokinetic processes will proceed. With respect to pharmacokinetics, disparate plasma concentration vs time curves of enantiomers may result from the pharmacokinetic processes proceeding at different rates for the two enantiomers. At their foundation, pharmacokinetic processes may be enantioselective at the levels of drug absorption, distribution, metabolism and excretion. In some circumstances, one enantiomer can be chemically or biochemically inverted to its antipode in a unidirectional or bidirectional manner. Genetic consideration such as polymorphic drug metabolism and gender, and patient factors such as age, disease state and concomitant drug intake can all play a role in determining the relative plasma concentrations of the enantiomers of a racemic drug. The use of a nonstereoselective assay method for a racemic compound can lead to difficulties in interpretation of data from, for example, bioequivalence or dose/concentration vs effect assessments. In this review data from a number of representative studies involving pharmacokinetics of chiral drugs are presented and discussed.

Septic Arthritis, Tenosynovitis, and Infections of Hoof Structures

Infectious diseases of synovial and hoof structures in horses can be devastating to soundness and can result in life-threatening complications. Timely diagnosis and early aggressive treatment can result in successful outcomes and resumption of athletic careers; however, delays in recognition and therapy can be the most costly reasons for failure. Sterilization of affected compartments and tissues requires removal of microorganisms and compromised tissue. Debridement, lavage, and appropriate antimicrobial drug use are the most reliable avenues of treatment. Antimicrobial drugs can be administered by local, regional, and systemic routes. Lavage techniques and debridement typically require surgical manipulations.