Nanoparticulate tablet dosage form of lisofylline-linoleic acid conjugate for type 1 diabetes: in situ single-pass intestinal perfusion (SPIP) studies and pharmacokinetics in rat.

Lisofylline (LSF) is an anti-inflammatory molecule with high aqueous solubility and rapid metabolic interconversion to its parent drug, pentoxifylline (PTX) resulting in very poor pharmacokinetic (PK) parameters, necessitating high dose and dosing frequency. In the present study, we resolved the physicochemical and pharmacokinetic limitations associated with LSF and designed its oral dosage form as a tablet for effective treatment in type 1 diabetes (T1D). Self-assembling polymeric micelles of LSF (lisofylline-linoleic acid polymeric micelles (LSF-LA PLM)) were optimized for scale-up (6 g batch size) and lyophilized followed by compression into tablets. Powder blend and tablets were evaluated as per USP. LSF-LA PLM tablet so formed was evaluated for in vitro release in simulated biological fluids (with enzymes) and for cell viability in MIN-6 cells. LSF-LA PLM in tablet formulation was further evaluated for intestinal permeability (in situ) along with LSF and LSF-LA self-assembled micelles (SM) as controls in a rat model using single-pass intestinal perfusion (SPIP) study. SPIP studies revealed 1.8-fold higher oral absorption of LSF-LA from LSF-LA PLM as compared to LSF-LA SM and ~5.9-fold higher than LSF (alone) solution. Pharmacokinetic studies of LSF-LA PLM tablet showed greater Cmax than LSF, LSF-LA, and LSF-LA PLM. Designed facile LSF-LA PLM tablet dosage form has potential for an immediate decrease in the postprandial glucose levels in patients of T1D.

Improved Oral Pharmacokinetics of Pentoxifylline with Palm Oil and Capmul® MCM Containing Self-Nano-Emulsifying Drug Delivery System.

Pentoxifylline (PTX), an anti-hemorrhage drug used in the treatment of intermittent claudication, is extensively metabolized by the liver resulting in a reduction of the therapeutic levels within a short duration of time. Self-nano-emulsifying drug delivery system (SNEDDS) is well reported to enhance the bio-absorption of drugs by forming nano-sized globules upon contact with the biological fluids after oral administration. The present study aimed to formulate, characterize, and improve the oral bioavailability of PTX using SNEDDS. The formulated SNEDDS consisted of palm oil, Capmul® MCM, and Tween® 80 as oil, surfactant, and co-surfactant, respectively. The mixture design module under the umbrella of the design of experiments was used for the optimization of SNEDDS. The dynamic light-scattering technique was used to confirm the formation of nanoemulsion based on the globule size, in addition to the turbidity measurements. In vivo bioavailability studies were carried out on male Wistar rats. The pharmacokinetic parameters upon oral administration were calculated using the GastroPlus software. The optimized SNEDDS had a mean globule size of 165 nm with minimal turbidity in an aqueous medium. Bioavailability of PTX increased 1.5-folds (AUC = 1013.30 ng h/mL) as SNEDDS than the pure drug with an AUC of 673.10 ng h/mL. In conclusion, SNEDDS was seen to enhance the bioavailability of PTX and can be explored to effectively control the incidents of intermittent claudication.

Effects of maturation and size on population pharmacokinetics of pentoxifylline and its metabolites in very preterm infants with suspected late-onset sepsis or necrotizing enterocolitis: a pilot study incorporating clinical outcomes.

AIMS: Infection-induced inflammation is associated with adverse long-term outcomes in preterm infants. Pentoxifylline (PTX) is a candidate for adjunct immunomodulatory therapy in preterm infants with late-onset sepsis (LOS) and necrotizing enterocolitis (NEC), but pharmacokinetic data in this population are extremely limited. This study aims to characterize the pharmacokinetic properties of intravenous PTX and its metabolites in preterm infants. METHOD: An open label pilot clinical study of intravenous PTX as an adjunct therapy in preterm infants (gestation <32 weeks) with suspected LOS or NEC was undertaken. PTX was infused for 12 h for two days (60 mg kg-1 per 12 h), and in infants with confirmed diagnosis of LOS or NEC, for 6 h for another 4 days (30 mg kg-1 per 6 h). Plasma concentrations of PTX and its principal metabolites from collected blood samples were measured using a validated LCMS assay. NONMEM was used to analyse the data using population pharmacokinetic modelling. RESULTS: The preterm infants (n = 26) had a median (range) gestation of 24.8 weeks (23.3-30.4) and birthweight of 689 g (370-1285). PTX was well tolerated and without treatment-limiting adverse effects. Changes in size (weight) and maturation were successfully modelled for PTX and metabolites. After allometric scaling, clearance increased with postmenstrual age, increasing by approximately 30% per week for PTX and M1 (lisofylline) and simulations of current dosing demonstrated a six-fold difference in exposure between 24 and 35 weeks postmenstrual age. CONCLUSIONS: The developed model can be used to explore dosing strategies based on size and maturation for preterm infants.

Influence of inflammatory disorders on pharmacokinetics of lisofylline in rats: implications for studies in humans.

1. Despite the number of favourable properties of lisofylline (LSF), clinical trials on this compound have not yielded the expected results yet. 2. The aims of this study were to evaluate the pharmacokinetics of LSF enantiomers in rats following intravenous, oral and subcutaneous administration of (±)-LSF and to assess the influence of experimental inflammatory disorders, such as multiple organ dysfunction syndrome and severe sepsis on LSF pharmacokinetics. 3. In addition, based on the results obtained an attempt was made to elucidate the possible reasons for the failure of LSF therapy in clinical trials carried out in patients with severe inflammatory disorders. 4. A subcutaneous route of (±)-LSF administration to rats is more favourable than an oral one due to a high bioavailability and a fast absorption of both LSF enantiomers. Pharmacokinetics of LSF in rats is significantly influenced by inflammatory diseases. Too low LSF serum levels might have been one of the reasons for clinical trial failures. A long-term i.v. infusion of LSF seems to be more effective compared to short-term multiple infusions that were used in clinical trials, as it may provide concentrations above IC50 for inhibition of both TNF-alpha release and cAMP degradation in serum for a longer period of time.

Self-assembling lisofylline-fatty acid conjugate for effective treatment of diabetes mellitus.

Lisofylline is an anti-inflammatory agent with proven anti-diabetic activity. Its high solubility and rapid metabolism results in poor bioavailability and short half-life, limiting its clinical utility. We have synthesized Lisofylline-Linoleic acid (LSF-LA) conjugate which self-assembled into micelles (156.9 nm; PDI 0.187; CMC 1 µg/mL; aggregation number 54) without any surfactant and showed enhanced cellular uptake. It protected MIN6 insulinoma cells from cytokine induced cell death and enhanced insulin production under inflammatory conditions. It also suppressed the proliferation of activated peripheral blood mononuclear cells and reduced the production of inflammatory cytokines, IFN-γ and TNF-α. LSF-LA micelles exhibited reduced protein binding, significantly higher half-life (5.7-fold) and higher apparent volume of distribution (5.3-fold) than free LSF. In T1D animals, reduced blood glucose levels were observed at a reduced dose (~15 mg/kg, once daily of LSF-LA micelles vs. 25 mg/kg, twice daily of free LSF) that was further confirmed by immunohistochemical analysis.

Pharmacokinetics of pentoxifylline and its 5-hydroxyhexyl metabolite following intravenous administration in cattle.

This study investigated the pharmacokinetics of pentoxifylline (PTX) and its 5-hydroxyhexyl metabolite (M-I) after single-dose intravenous (IV) administration (10 mg/kg) of PTX in six healthy cattle. The safety of PTX was evaluated by clinical observation and biochemical analysis. Plasma concentrations of PTX and M-I were simultaneously determined by reverse-phase high performance liquid chromatography. Pharmacokinetic parameters were calculated using non-compartmental methods. Salivation and discomfort were observed for 2 h following the drug administration. Serum direct bilirubin, total bilirubin, and phosphorus levels at 24 h following the drug administration were significantly different from the control values (0 h) (P < 0.05). Pharmacokinetic variables of PTX were characterized by a short terminal elimination half-life (1.05 ± 0.19 h), a large volume of distribution (6.30 ± 1.76 L/kg), and high total body clearance (5.31 ± 1.27 L/h/kg). The mean ratio between the area under the concentration-time curves of M-I and PTX was 1.34. These results indicate that single-dose administration of PTX at 10 mg/kg IV in cattle resulted in therapeutic concentrations similar to those observed in humans and horse. However, further studies are necessary to determine the safety and pharmacokinetics following repeated administrations of PTX.

Enhanced anticancer efficacy of histone deacetyl inhibitor, suberoylanilide hydroxamic acid, in combination with a phosphodiesterase inhibitor, pentoxifylline, in human cancer cell lines and in-vivo tumor xenografts.

Vorinostat [suberoylanilide hydroxamic acid (SAHA)], a histone deacetylase inhibitor, shows limited clinical activity against solid tumors when used alone. The methyl xanthine drug, pentoxifylline (PENT), has been described to have antitumor properties. The aim of this study was to look for the enhanced anticancer activities of both agents when used in combination at doses lower than their respective efficacy dose when used alone. We investigated the antitumor potential of this novel combination in vitro and in vivo. The combination index was assessed for these two drugs to look for synergistic antiproliferative activity against a broad spectrum of human cancer cell lines. Consistent additive to synergistic interactions were observed in HCT116 cells when PENT was combined with SAHA at all drug tested concentrations. The combination of SAHA and PENT induces chromatin condensation and apoptosis downstream of the pan histone deacetylase inhibition and phosphodiesterase regulation, leading to subsequent cell cycle arrest at their lower tested concentrations. Further, the ability of this combination to inhibit angiogenesis, both in vitro and in vivo, was examined and a significant inhibition in tube formation in HUVEC cells and neovascularization of Matrigel plug was observed. A significant inhibition in tumor growth was observed in severe combined immunodeficient mice bearing HCT116 (colon) and PC3 (prostate) human xenografts treated with SAHA (30 mg/kg, intraperitoneal) in combination with PENT (60 mg/kg, intraperitoneal), with no loss in body weight and 100% survival. In conclusion, these findings indicate the enhanced anticancer activity of SAHA in combination with PENT both in vitro and in vivo.

Uroprotective effect of pentoxifylline in cyclophosphamide-induced hemorrhagic cystitis in rats.

The role of phosphodiesterase inhibitor, pentoxifylline, in the prevention of cyclophosphamide-induced hemorrhagic cystitis was evaluated in a rat model. Hemorrhagic cystitis was induced in rats by an intraperitoneal (i.p.) injection of a single dose of cyclophosphamide (150 mg/kg). Pentoxifylline (150 mg/kg/day/ip) was administered for 10 days followed by cyclophosphamide. Hemorrhagic cystitis was well characterized macroscopically, microscopically, and biochemically. Cyclophosphamide induced bladder injury including acute severe inflammation, vascular congestion, severe edema, hemorrhage, inflammatory cell infiltration in the lamina propria, and epithelial denudation; as well as it notably elevated serum inflammatory cytokines (tumor necrosis factor-α, interleukin-6, and interleukin-1ß), bladder content of malondialdehyde and total nitrate, accompanied with depletion of bladder antioxidant enzymes activities (glutathione peroxidase, superoxide dismutase, glutathione-S-transferase, and catalase). Prior administration of pentoxifylline improved all biochemical and histologic alterations induced by the cytotoxic drug cyclophosphamide. In conclusion, pentoxifylline has proven uroprotective efficacy in the cyclophosphamide-induced hemorrhagic cystitis model, possibly through modulating the release of inflammatory cytokines and nitric oxide and restoring the oxidant/antioxidant balance.

Development and Validation a UPLC-MS/MS Method for Quantification of Pentoxifylline in Beagle Plasma: Application for Pharmacokinetic Study of Food Effect.

Purpose: To develop an UPLC-MS/MS method for the quantitative analysis of pentoxifylline in beagle dog plasma and apply it to a pharmacokinetic study of food effect. Methods: Sample separation was achieved using a Kinetex Phenyl-Hexyl column (50 × 2.1 mm, 1.7 µm) with a gradient elution program in 5.5 min after a simple protein precipitation with methanol. Using the mobile phase that made up by 0.2% formic acid and 5mM ammonium formate water (A) and methanol (B). Quantitation was carried out using the positive ionization mode with multiple reaction monitoring (MRM). A randomized, single-dose, two-period crossover study was conducted in six fasted or fed beagles that received 400 mg pentoxifylline sustained-release tablets (Brand name: Shuanling™, CSPC Pharmaceutical Group). WinNonlin® software was used to calculate pharmacokinetic parameters. Results: The linear calibration range was 2-1000 ng/mL (r2> 0.99). Both intra- and inter-batch precision were less than 6.27%, and the accuracy ranged from 88.65% to 97.18%. Pentoxifylline was readily absorbed in fasted and fed dogs administered a dose of 400 mg (tmax:1.54h vs 1.83h). Compared to the fasted group, the AUC0→t and Cmax in the fed group increased by 1.71-fold and 1.30-fold, respectively. In the fasted group, the AUC0→t and Cmax values were 4684.08 h•ng/mL and 2402.33 ng/mL, respectively. In the fed group, these values were 8027.75 h•ng/mL and 3119.67 ng/mL. The difference in AUC0-t between the fed and fasted group was statistically significant. Conclusion: The novel optimized UPLC-MS/MS assay is an effective tool for the determination of pentoxifylline and has been successfully applied in pharmacokinetic studies of pentoxifylline in beagle dogs. The administration of pentoxifylline sustained-release tablets with food significantly increased the area under the time curve, and it is recommended that they should be administered during or shortly after feeding.

Effect of pentoxifylline and 5-fluorouracil/triamcinolone on laryngotracheal stenosis developing as a complication of tracheostomy: study in rats.

We aimed to investigate the prophylactic effect of pentoxifylline (PTX) and 5-fluorouracil (5-FU) on laryngotracheal stenosis in tracheotomised rats by evaluating blood glutathione peroxidase (GPx) and superoxide dismutase activities and by histopathological evaluation of laryngotracheal segment. Randomized prospective single-blind study. Standard vertical tracheotomy was performed on 24 rats. Then, the animals were randomly divided into three groups. Intraperitoneal PTX administered to group A (study group) for 10 days. 5-FU was injected in paratracheal tissues in group B (study group) for 10 days. In group C (control group), intraperitoneal saline was administered for 10 days. After 10 days, tracheal cannules were removed. For biochemical analysis, two blood samples were obtained. Three weeks later, all animals were euthanized and trachea specimens were harvested. Stenosis index and mean wall thickness in PTX group were lower as compared to other groups but the difference was statistically insignificant. Minimum inflammation and fibrosis plus maximum epithelial regeneration were seen in PTX group. In addition, GPx activity was at highest level in PTX group and a statistically significant difference was found between control and PTX groups (P = 0.024) though the difference between remaining groups was statistically insignificant (P = 0.121). Superoxide dismutase activity was highest in PTX group but no statistically significant difference was found between the three groups (P = 0.305). The administration of PTX increases GPx activity and it may have some effect on tracheal scar formation which develops following tracheostomy.

Successful treatment of life-threatening pentoxifylline intoxication by high-flux hemodialysis.

High-flux hemodialysis is the method of choice for the treatment of many life threatening intoxications. Reports on intoxication with pentoxifylline are rare, and although pharmacokinetic properties of the drug suggest a potential role for hemodialysis, there are no published reports on extracorporeal treatment attempts. We report the first case of successful treatment of potentially life-threatening pentoxifylline intoxication by high-flux hemodialysis. Based on this single case, dialysis should be considered, especially in anuric patients with pentoxifylline intoxication.

Application of liquid chromatography-tandem mass spectrometry method for the simultaneous quantitative analysis of propentofylline and its chiral metabolite M1 in rats.

A sensitive and selective liquid chromatographic-electrospray ionization mass spectrometric method for the simultaneous determination of propentofylline and enantiomers of its active metabolite M1 in rat serum, cortex and hippocampus was developed and validated according to GLP procedures. Sample preparations were carried out by liquid-liquid extraction using diethyl ether after the addition of the internal standard (pentoxifylline). The dried residue was reconstituted in mobile phase and injected onto a Chiralpak AD column (10 µm, 250 × 4.6 mm i.d.). The limit of quantification for propentofylline in serum, cortex and hippocampus was set at 0.25 ng/mL and for enantiomers of its metabolite M1 at 1.25 ng/mL. The established LC/ESI-MS/MS method has been successfully applied to an initial pharmacokinetic study of propentofylline and also to assessment of distribution of parent drug and enantiomers of its pharmacologically active metabolite M1 to cortex and hippocampus after intravenous administration of propentofylline to rats at a dose of 5 mg/kg.

[Influence of perftoran on pharmacokinetics of hydrophilic drugs].

Influence of perfluorocarbon blood substitute Perftoran on pharmacokinetics of cefazolin (20 mg/kg), cefotaxime (25 mg/kg), ciprofloxacin (4 mg/kg) and pentoxifylline (10 mg/kg) upon their intravenous introduction separately or immediately after Perftoran infusion (5 ml/kg) was investigated on rabbits. It was found that the presence of Perftoran accelerated the transfer from blood to tissues for Cefazolin and Cefotaxime, which have negative values of the distribution logarithm in octanol/water (logP = -0.4 and -1.4, respectively). With respect to pentoxifylline and ciprofloxacin, which are less hydrophilic, the effect of pharmacokinetic interference was either weaker or absent. Probably, the infusion of hydrophobic Perftoran nanoemulsion enhances the hydrophobicity of blood plasma, which is a prerequisite for the more intensive transfer of hydrophilic ligands from blood to tissues.

Pentoxifylline as an adjunct therapy in children with cerebral malaria.

BACKGROUND: Pentoxifylline (PTX) affects many processes that may contribute to the pathogenesis of severe malaria and it has been shown to reduce the duration of coma in children with cerebral malaria. This pilot study was performed to assess pharmacokinetics, safety and efficacy of PTX in African children with cerebral malaria. METHODS: Ten children admitted to the high dependency unit of the Kilifi District Hospital in Kenya with cerebral malaria (Blantyre coma score of 2 or less) received quinine plus a continuous infusion of 10 mg/kg/24 hours PTX for 72 hours. Five children were recruited as controls and received normal saline instead of PTX. Plasma samples were taken for PTX and tumour necrosis factor (TNF) levels. Blantyre Coma Score, parasitemia, hematology and vital signs were assessed 4 hourly. RESULTS: One child (20%) in the control group died, compared to four children (40%) in the PTX group. This difference was not significant (p = 0.60). Laboratory parameters and clinical data were comparable between groups. TNF levels were lower in children receiving PTX. CONCLUSIONS: The small sample size does not permit definitive conclusions, but the mortality rate was unexpectedly high in the PTX group.

Pharmacokinetic-pharmacodynamic modeling of methylxanthine derivatives in mice challenged with high-dose lipopolysaccharide.

AIMS: Pentoxifylline and lisofylline are methylxanthine derivatives that exhibit anti-inflammatory activity both in vitro and in vivo. This study was designed to develop a pharmacokinetic-pharmacodynamic (PK/PD) model to describe the inhibitory effect of these compounds on TNF-alpha production in mice challenged with bacterial lipopolysaccharide (LPS). METHODS: Male CD-1 mice received increasing intravenous doses of either compound simultaneously with high-dose LPS. A 2-compartment model with Michaelis-Menten-type elimination was used to describe the drug concentration versus time data. Serum TNF-alpha levels were fitted to an indirect response model. RESULTS: Pentoxifylline and lisofylline reduced LPS-induced TNF-alpha serum concentrations in a dose-dependent manner. PK/PD analysis revealed an almost 2-fold higher estimate of K(m) for pentoxifylline in comparison to lisofylline. The production and elimination rates of TNF-alpha were: k(in) = 2,167 pg/ml * h(-1) and k(out) = 1.65 h(-1), respectively. The drug concentration causing 50% of TNF inhibition (IC(50)) was markedly lower for pentoxifylline (0.47 vs. 1.61 microg/ml). CONCLUSIONS: It seems that pentoxifylline is more potent than lisofylline in inhibiting TNF-alpha production in vivo. The proposed PK/PD model allowed a better understanding of the pharmacological properties of both methylxanthine derivatives and may be helpful in appropriate dosage selection for further studies.

Enhancement of oral bioavailability of pentoxifylline by solid lipid nanoparticles.

Pentoxifylline (PTX) is a highly water-soluble, hemorheologic drug that undergoes first-pass effect with 20% bioavailability. The solid lipid nanoparticles (SLNs) of PTX were prepared to enhance its oral bioavailability by homogenization, followed by the sonification method. Seven different variables, each at two levels, were studied: lipid type, surfactant type and concentration, speed of homogenizer, acetone:dichloromethane (DCM) ratio, lecithin:lipid ratio, and sonication time. The mean particle size and size distribution, drug entrapment efficiency (EE%), zeta potential, and drug release of the SLNs were investigated. A pharmacokinetic study was conducted in male Wistar rats after oral administration of 10 mg kg(-1) PTX in the form of free drug or SLNs. The z-average particle size, zeta potential, and EE% of the SLNs were at least 250 nm, -30.2 mV, and 70%, respectively. Among the studied factors, the lipid type, surfactant type, and percentage had a significant effect on the particle size. Zeta potential was more affected by lipid type, acetone:DCM ratio, and sonication time. Speed of homogenizer and acetone:DCM ratio had a significant effect on the EE%. The optimized SLN was prepared by 80 mg of cetyl alcohol, 10 mg of lecithin, acetone:DCM ratio (1:2), 30-second sonication, 3% Tween 20, and a mixing rate of 800 rpm. In vitro drug release lasted for about 5 hours. It was found that the relative bioavailability of PTX in SLNs was significantly increased, compared to that of the PTX solution. SLNs offer a promising approach to improve the oral bioavailability of PTX that is affected by a high first-pass effect.

Validation of an HPLC method for determination of pentoxifylline in human plasma and its application to pharmacokinetic study.

An HPLC method suitable for routine determination of pentoxifylline in human plasma has been adapted and validated. Sample preparation was done by solid-phase extraction. Chloramphenicol was used as the internal standard. The linear range was from 15-400 ng/mL (r2 = 0.9994), with a limit of quantitation of 15 ng/mL. The limit of detection was found to be 5 ng/mL. The intra- and interday accuracy ranged from 98.0 to 110.2% and the coefficient of variation was not more than 8.8% for both intra- and interday precision. The absolute recoveries of pentoxifylline and chloramphenicol from human plasma were >97%. The method was validated with excellent specificity, accuracy, precision, recovery, and stability. The pharmacokinetic study of a generic pentoxifylline 400 mg tablet in healthy Thai male volunteers after a single dose administration was determined by this developed assay.

Validation of a high-performance liquid chromatography method for pharmacokinetic evaluation of pentoxifylline and lisofylline in rat serum and tissues.

The aim of this paper was to validate an analytical method for the simultaneous determination of PTX and its active metabolite (-)-(R)-M1 in rat serum and some tissues using a high-performance liquid chromatography method with ultraviolet detection (HPLC-UV). The specificity, linearity, precision, accuracy, recovery, lower limit of detection, lower limit of quantification and stability study were successively conducted according to GLP procedures. HPLC separation of all compounds was carried out on a normal-phase ChiralPak AD column (250 mm x 4.6 mm i.d., 5 mm), using, as a mobile phase, a mixture of hexane and 2-propanol (84:16, v/v) containing 0.01% of diethylamine with a flow rate of 1.5 mL x min(-1). The calibration curves from all studied matrices were linear across the concentration range from 0.01 to 100 mg x mL(-1) with a lower limit of quantification of 0.01 microg x mL(-1) for all analytes. The application of the assay to a pilot pharmacokinetic study and tissue distribution of the compounds in rats after intraperitoneal dosing of 50 mg x kg(-1) of PTX was described. Significant (p<0.05) differences between serum and tissue levels of PTX, (-)-(R)-M1 and (+)-(S)-M1 were observed.

Development and validation of bioanalytical liquid chromatography-tandem mass spectrometry method for the estimation of pentoxifylline in human plasma: Application for a comparative pharmacokinetic study.

A method for bioanalysis of pentoxifylline in human plasma was developed using liquid chromatography-tandem mass spectrometry, which is simple, specific, and sensitive. Pentoxifylline D5 was used as the internal standard. Employing only 100 µl of human plasma, processing was done with solid-phase extraction technique. The analyte and the internal standard were separated from endogenous components on Ace phenyl column using a mixture of 5 mM ammonium acetate buffer and high performance liquid chromatography grade acetonitrile (60:40, v/v) as mobile phase at a flow rate of 1 ml/min. The linearity of the method was in the range of 3-1200 ng/ml with r2 > 0.99. Positive ion MRM mode was used for the detection of the analyte and the internal standard. The method was validated as per the US Food and Drug Administration guidelines and the results were within the acceptance limits. The proposed method was applied for comparative pharmacokinetic study of pentoxifylline after oral administration of 400 and 600 mg tablets to South Indian male subjects under fed conditions.

Pharmacokinetics of pentoxifylline and its 5-hydroxyhexyl metabolite after intravenous administration of increasing doses to sheep.

OBJECTIVE: To determine the pharmacokinetics of pentoxifylline (PTX) and its 5-hydroxyhexyl metabolite (M-I) after IV administration of increasing doses of PTX to sheep. ANIMALS: 6 healthy adult Merino sheep. PROCEDURES: Each sheep received 10-, 20-, and 40-mg/kg doses of PTX, IV, with a 15-day washout period between doses. Blood samples were collected before and at predetermined times after administration of each dose to determine plasma PTX and M-I concentrations by high-performance liquid chromatography. Pharmacokinetic parameters for PTX and M-I were estimated by noncompartmental analysis. RESULTS: No adverse effects were observed after administration of the 10- and 20-mg/kg doses. Following administration of the 40-mg/kg dose, all sheep developed tachycardia and hypersalivation and appeared agitated for approximately 4 hours. Plasma PTX concentrations considered therapeutic in other species were achieved in all sheep after administration of all 3 doses. Pharmacokinetic parameters for PTX and M-I varied in a dose-dependent linear manner. For PTX, the mean area under the concentration-time curve (AUC), elimination half-life, and volume of distribution increased with dose and ranged from 15.67 to 94.66 h·µg/mL, 0.68 to 0.91 hours, and 0.55 to 0.66 L/kg, respectively, whereas clearance decreased with dose and ranged from 0.42 to 0.64 L/h/kg. The mean ratio of the AUC for M-I to AUC for PTX ranged from 0.38 to 0.46. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that pharmacokinetic parameters for PTX and M-I varied in a dose-dependent linear manner in healthy sheep. Further studies are warranted to determine the therapeutic threshold and optimal dosage for PTX in sheep.