Bioavailability of racemic ibuprofen and its lysinate from suppositories in rabbits

Efficacy and safety of rectal ibuprofen for patent ductus arteriosus closure in very low birth weight preterm infants

BACKGROUND

To compare rectal ibuprofen with oral ibuprofen for the closure of hemodynamically significant patent ductus arteriosus (hsPDA) in very low birth weight (VLBW) preterm infants.

STUDY DESIGN AND SUBJECTS

In a prospective, randomized study, 72 VLBW infants who had hsPDA received either rectal or oral ibuprofen. The plasma concentration of ibuprofen and renal functions were determined in both groups by the high-performance liquid chromatography (HPLC) method and cystatin-C (cys-C), respectively.

RESULTS

The hsPDA closure rate of the group that received rectal ibuprofen was similar to oral ibuprofen (86.1% versus 83.3%) after the first course of the treatment (p = 0.745). A statistically significant difference was identified between the mean plasma cys-C levels before and after treatment in both the rectal and oral ibuprofen groups (p = 0.004 and p< 0.001, respectively). The mean plasma ibuprofen concentration was similar in both groups after the first dose (rectal 44.06 ± 12.4; oral, 48.28 ± 22.8) and the third dose (rectal, 45.34 ± 24.3; oral, 48.94 ± 24.8) (p > 0.05 for all values).

CONCLUSIONS

Rectal ibuprofen is as effective as oral ibuprofen for hsPDA closure in VLBW infants. The rise in the cys-C level with rectal and oral treatment shows that patients with borderline renal function should be evaluated and followed closely.

High performance capillary electrophoresis for determination of the enantiomers of 2-arylpropionic acid derivatives in human serum

A stereospecific capillary zone electrophoresis (CZE) method for determination of the enantiomers of some 2-arylpropionic acid derivatives (2-APA, profens) in human serum has been developed. Racemic-ibuprofen (rac-IBP), racemic-flurbiprofen (rac-FBP), racemic-ketoprofen (rac-KTP) and (+)-S-naproxen ((+)-S-NPX--an internal standard) were chosen for these studies. The 2-APA enantiomers were extracted from acidified serum samples using methylene chloride separated in a fused silica capillary. The capillary was filled with a background electrolyte, which consisted of 0.05 M heptakis 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbetaCD) (chiral selector) in 0.02 M triethanolamine-phosphate buffer of pH 5.0. Separation and resolution of the enantiomer mixture were obtained in one analytical run. The calculated electrophoretic parameters of the analytes were as follows: electrophoretic mobility, micorep(-)-R = -0.75 x 10(-4) to -0.30 x 10(-4) cm2/Vs; micorep(+)-S = -0.83 -(-0.38) cm2/Vs and electroosmotic mobility, microEOF = 2.35 x 10(-4) cm2/Vs, migration times, tmigr R = 12.55 - 16.07 min; tmigr s = 13.08 - 16.9 min, resolution factors, RS = 1.88 - 3.70 and chiral selectivity, alpha = 1.16 - 1.34. The method developed for the enantiomers was validated. The calibration curves were linear in the range of 0.5-50.0 microg/ml for FBP or KTP and of 1.0-50.0 microg/ml for IBP enantiomer concentrations. Recovery of the enantiomers from serum was about 90%. At the limit of quantification (LOQ) precision and accuracy were within 15%. The validated method was successfully applied to pharmacokinetic and bioavailability studies on KTP enantiomers in humans after administration of standard and sustained release tablets of rac-KTP. Significant differences in the pharmacokinetic parameters of both formulations were observed and the studied formulations were not bioequivalent.

Enhanced rectal bioavailability of ibuprofen in rats by poloxamer 188 and menthol

To improve the bioavailability of poorly water-soluble ibuprofen in the rectum with poloxamer and menthol, the effects of menthol and poloxamer 188 on the aqueous solubility of ibuprofen were investigated. The dissolution and pharmacokinetic study of ibuprofen delivered by the poloxamer gels composed of poloxamer 188 and menthol were then performed. In the absence of poloxamer, the solubility of ibuprofen increased until the ratio of menthol to ibuprofen increased from 0:10 to 4:6 followed by an abrupt decrease in solubility above the ratio of 4:6, indicating that four parts menthol formed eutectic mixture with six parts ibuprofen. In the presence of poloxamer, the solutions with the same ratio of menthol to ibuprofen showed abrupt increase in the solubility of ibuprofen. The poloxamer gel with menthol/ibuprofen ratio of 1:9 and higher than 15% poloxamer 188 showed the maximum solubility of ibuprofen, 1.2mg/ml. Menthol improved the dissolution rates of ibuprofen from poloxamer gels. Release mechanism showed that the release rate of ibuprofen from the poloxamer gels without menthol was independent of the time but the drug might be released from the poloxamer gels with menthol by Fickian diffusion. Furthermore, the poloxamer gel with menthol (poloxamer/menthol/ibuprofen (15%/0.25%/2.5%)) gave significantly higher initial plasma concentrations, C(max) and AUC of ibuprofen than did solid suppository, indicating that the drug from poloxamer gel could be more absorbed than that from solid one in rats. Thus, the poloxamer gel with poloxamer 188 and menthol was a more effective rectal dosage form for ibuprofen.

Stereoselective pharmacokinetics of ibuprofen and its lysinate from suppositories in rabbits

Studies were performed on the effect of ibuprofen racemate ionisation extent on the pharmacokinetics of its enantiomers following administration in suppositories to rabbits. The suppositories, containing 146.3 mg ibuprofen in acidic form (IBP) or 250 mg ibuprofen lysinate (IBPL), equivalent to the above IBP dose, were prepared using lipophilic Witepsol H-15 as a base and administered to rabbits in a crossover design. Compared with IBP, administration of IBPL was followed by faster absorption and elimination of R and S enantiomers. However, significant differences at alpha=0.05 were observed only at the stage of elimination. AUC was markedly higher following administration of suppositories containing IBP than following suppositories with IBPL and this pertained to both R and S enantiomers. Evident inversion of R into S form was noted 30 min following IBPL administration and 1 h after IBP administration. Ionisation extent only insignificantly affected the scope of chiral inversion of ibuprofen R into S form (AUC(S-IBP)/AUC(R-IBP)=1.66, AUC(S-IBPL)/AUC(R-IBPL)=1.57). No presystemic inversion of R into S was observed in rabbits following administration of IBP or IBPL in suppositories. IBP enantiomers were isolated from 0.5 ml serum using solid phase extraction in C(18) columns and were quantified by HPLC using the chiral Whelk O1 column and UV detector (lambda=264 nm).