Pharmacokinetics and absolute bioavailability of ibuprofen after oral administration of ibuprofen lysine in man

An Explanation of Why Dose-Corrected Area Under the Curve for Alternate Administration Routes Can Be Greater than for Intravenous Dosing

It is generally believed that bioavailability (F) calculated based on systemic concentration area under the curve (AUC) measurements cannot exceed 1.0, yet some published studies report this inconsistency. We teach and believe, based on differential equation derivations, that rate of absorption has no influence on measured systemic clearance following an oral dose, i.e., determined as available dose divided by AUC. Previously, it was thought that any difference in calculating F from urine data versus that from systemic concentration AUC data was due to the inability to accurately measure urine data. A PubMed literature search for drugs exhibiting F > 1.0 and studies for which F was measured using both AUC and urinary excretion dose-corrected analyses yielded data for 35 drugs. We show and explain, using Kirchhoff's Laws, that these universally held concepts concerning bioavailability may not be valid in all situations. Bioavailability, determined using systemic concentration measurements, for many drugs may be overestimated since AUC reflects not only systemic elimination but also absorption rate characteristics, which is most easily seen for renal clearance measures. Clearance of drug from the absorption site must be significantly greater than clearance following an iv bolus dose for F(AUC) to correctly correspond with F(urine). The primary purpose of this paper is to demonstrate that studies resulting in F > 1.0 and/or greater systemic vs urine bioavailability predictions may be accurate. Importantly, these explications have no significant impact on current regulatory guidance for bioequivalence testing, nor on the use of exposure (AUC) measures in making drug dosing decisions.

Isopropyl Amino Acid Esters Ionic Liquids as Vehicles for Non-Steroidal Anti-Inflammatory Drugs in Potential Topical Drug Delivery Systems with Antimicrobial Activity

New derivatives of non-steroidal anti-inflammatory drugs were synthesized via conjugation with L-amino acid isopropyl esters. The characteristics of the physicochemical properties of the obtained pharmaceutically active ionic liquids were determined. It has been shown how the incorporation of various L-amino acid esters as an ion pair affects the properties of the parent drug. Moreover, the antimicrobial activity of the obtained compounds was evaluated. The proposed structural modifications of commonly used drugs indicate great potential for use in topical and transdermal preparations.

Evaluating the IVIVC by Combining Tiny-TIM Outputs and Compartmental PK Model to Predict Oral Exposure for Different Formulations of Ibuprofen

Nowadays, the ever-increasing costs of research and development in the pharmaceutical industry have created a big demand for predicting the performances of drug candidates. Of those, the desire to establish an in vitro-in vivo correlation (IVIVC) to better predict the oral drug exposure for different drug products is a growing need. Once a robust IVIVC is established, the performance of different drug products can be predicted and selected for testing in clinical trials with greater confidence. This tool will significantly reduce the cost and speed of drug development and provide new therapy to the patient faster. In this study, we explore combining the outputs of Triskelion's Gastro-Intestinal Model (Tiny-TIM) and multi-compartment pharmacokinetic model for a 200 mg ibuprofen product. The Loo-Riegelman method was used to calculate the amount of ibuprofen absorbed and was combined with the Tiny-TIM data to establish the IVIVC. The IVIVC was used to predict the exposures of both fast release and liquid gel formulations in humans. In general, the predicted exposure using Tiny-TIM-based IVIVC has good agreement with the clinical findings.

Predicting the Human Hepatic Clearance of Acidic and Zwitterionic Drugs

Prospective predictions of human hepatic clearance for anionic/zwitterionic compounds, which are oftentimes subjected to transporter-mediated uptake, are challenging in drug discovery. We evaluated the utility of preclinical species, rats and cynomolgus monkeys [nonhuman primates (NHPs)], to predict the human hepatic clearance using a diverse set of acidic/zwitterionic drugs. Preclinical clearance data were generated following intravenous dosing in rats/NHPs and compared to the human clearance data (n = 18/27). Single-species scaling of NHP clearance with an allometric exponent of 0.50 allowed for good prediction of human clearance (fold error ∼2.1, bias ∼1.0), with ∼86% predictions within 3-fold. In comparison, rats underpredicted the clearance of lipophilic acids, while overprediction was noted for hydrophilic acids. Finally, an in vitro clearance assay based on human hepatocytes, which is routinely used in discovery setting, markedly underpredicted human clearance (bias ∼0.12). Collectively, this study provides insights into the usefulness of the preclinical models in enabling pharmacokinetic optimization for acid/zwitterionic drug candidates.

Predictability of human pharmacokinetics of drugs that undergo hepatic organic anion transporting polypeptide (OATP)-mediated transport using single-species allometric scaling in chimeric mice with humanized liver: integration with hepatic drug metabolism

We previously reported a prediction method for human pharmacokinetics (PK) using single species allometric scaling (SSS) and the complex Dedrick plot in chimeric mice with humanized liver to predict the total clearance (CL_t), distribution volumes in steady state (Vd_ss) and plasma concentration-time profiles of several drugs metabolized by cytochrome P450 (P450) and non-P450 enzymes. In the present study, we examined eight compounds (bosentan, cerivastatin, fluvastatin, pitavastatin, pravastatin, repaglinide, rosuvastatin, valsartan) as typical organic anion transporting polypeptide (OATP) substrates and six compounds metabolized by P450 and non-P450 enzymes to evaluate the predictability of CL_t, Vd_ss and plasma concentration-time profiles after intravenous administration to chimeric mice. The predicted CL_t and Vd_ss of drugs that undergo OATP-mediated uptake and P450/non-P450-mediated metabolism reflected the observed data from humans within a threefold error range. We also examined the possibility of predicting plasma concentration-time profiles of drugs that undergo OATP-mediated uptake using the complex Dedrick plot in chimeric mice. Most profiles could be superimposed with observed profiles from humans within a two- to threefold error range. PK prediction using SSS and the complex Dedrick plot in chimeric mice can be useful for evaluating drugs that undergo both OATP-mediated uptake and P450/non-P450-mediated metabolism.

Assessing the impact of cystic fibrosis on the antipyretic response of ibuprofen in children: Physiologically-based modeling as a candle in the dark

AIM

The goal of this study is to present the utility of quantitative modelling for extrapolation of drug safety and efficacy to underrepresented populations in controlled clinical trials. To illustrate this, the stepwise development of an integrated disease/pharmacokinetics/pharmacodynamics model of antipyretic efficacy of ibuprofen in children with cystic fibrosis (CF) is presented along with therapy optimization suggestions.

METHOD

Published clinical trials, in vitro data, and drug physiochemical properties were used to develop an ibuprofen-mediated antipyresis model for febrile children also having CF. Workflow included first developing a mechanistic absorption model using in vitro-in vivo extrapolation followed by physiologically-based pharmacokinetic (PBPK) modelling. The verified PBPK model was then scaled to paediatric patients with CF. Once verified, the PBPK model was linked to an indirect response model of antipyresis for simulation of the overall antipyretic efficacy of ibuprofen in CF children.

RESULTS

Model simulations showed therapeutic inequivalence between healthy children and paediatric patients with CF; C_max and AUC decreased by 39% (32-46%) and 44% (36-52%), respectively, in patients. Further, and in agreement with literature reports, predicted pharmacodynamics time courses suggest a slower onset and faster offset of action in patients compared to healthy children, 30 and 60 minutes, respectively. Exploratory simulations suggest an increase in dosing frequency for CF children as a better therapeutic strategy.

CONCLUSION

Model-informed approaches to leveraging knowledge obtained throughout the life cycle of drug development may play a key role in extrapolating drug efficacy and safety to underrepresented populations.

A target concentration strategy to determine ibuprofen dosing in children

BACKGROUND

Ibuprofen is widely used for ductus arteriosus closure in premature neonates and for analgesia in children and adults. There are no maturation descriptors of clearance. This lack of maturation understanding limits dosing recommendations from premature neonates to adulthood.

METHODS

Published clearance estimates from different aged patients determined after administration from time-concentration profiles were used to construct a maturation model based on size and age. Curve fitting was performed using nonlinear mixed-effects models. A target concentration strategy was used to estimate maintenance dose at different ages.

RESULTS

There were three publications reporting an estimate of individual clearance estimates in premature neonates, three reporting population clearances in infants, 11 in children 2-15 years (1 with individual and 9 with population clearances), and 13 adult studies (1 with individual and 12 with population clearances). Clearance maturation, standardized to a 70 kg person was described using the Hill equation. Mature clearance was 3.81 (CV 15.5%, 95%CI 3.72, 3.92) L/h/70 kg. The maturation half-time was 36.8 (CV 9.2%, 95%CI 34.7, 40.9) weeks postmenstrual age and the Hill coefficient 11.5 (95%CI 8.1, 15). A target effect of four units (visual analogue scale 0-10) correlated with an effect site concentration of 6.3 mg/L: a concentration achieved at trough after 400 mg 8 hourly in adults.

CONCLUSION

Previously published pharmacokinetic parameters can be used to develop maturation models that address gaps in current knowledge regarding the influence of age on a drug's disposition. Maturation of ibuprofen clearance was rapid and was 90% of adult values by the first month of life in term neonates (ie, 44 weeks postmenstrual age) and 98% of standardized adult estimates by 3 months of age (53 weeks postmenstrual age). Clearance informed dosing predictions in all ages (premature neonate to adult) and matched those doses in common use in children older than 3 months.

Thiodipeptides targeting the intestinal oligopeptide transporter as a general approach to improving oral drug delivery

The broad substrate capacity of the intestinal oligopeptide transporter, PepT1, has made it a key target of research into drug delivery. Whilst the substrate capacity of this transporter is broad, studies have largely been limited to small peptides and peptide-like drugs. Here, we demonstrate for the first time that a diverse range of drugs can be targeted towards transport by PepT1 using a hydrolysis resistant carrier. Eleven prodrugs were synthesized by conjugating modified dipeptides containing a thioamide bond to the approved drugs ibuprofen, gabapentin, propofol, aspirin, acyclovir, nabumetone, atenolol, zanamivir, baclofen and mycophenolate. Except for the aspirin and acyclovir prodrugs, which were unstable in the assay conditions and were not further studied, the prodrugs were tested for affinity and transport by PepT1 expressed in Xenopus laevis oocytes: binding affinities ranged from approximately 0.1 to 2 mM. Compounds which showed robust transport in an oocyte trans-stimulation assay were then tested for transcellular transport in Caco-2 cell monolayers: all five tested prodrugs showed significant PepT1-mediated transcellular uptake. Finally, the ibuprofen and propofol prodrugs were tested for absorption in rats: following oral dosing the intact prodrugs and free ibuprofen were measured in the plasma. This provides proof-of-concept for the idea of targeting poorly bioavailable drugs towards PepT1 transport as a general means of improving oral permeability.

Formulation and delivery strategies of ibuprofen: challenges and opportunities

Ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), is mostly administered orally and topically to relieve acute pain and fever. Due to its mode of action this drug may be useful in the treatment regimens of other, more chronic conditions, like cystic fibrosis. This drug is poorly soluble in aqueous media and thus the rate of dissolution from the currently available solid dosage forms is limited. This leads to poor bioavailability at high doses after oral administration, thereby increasing the risk of unwanted adverse effects. The poor solubility is a problem for developing injectable solution dosage forms. Because of its poor skin permeability, it is difficult to obtain an effective therapeutic concentration from topical preparations. This review aims to give a brief insight into the status of ibuprofen dosage forms and their limitations, particle/crystallization technologies for improving formulation strategies as well as suggesting its incorporation into the pulmonary drug delivery systems for achieving better therapeutic action at low dose.

A physiologically based pharmacokinetic model to predict the pharmacokinetics of highly protein-bound drugs and the impact of errors in plasma protein binding

Predicting the pharmacokinetics of highly protein-bound drugs is difficult. Also, since historical plasma protein binding data were often collected using unbuffered plasma, the resulting inaccurate binding data could contribute to incorrect predictions. This study uses a generic physiologically based pharmacokinetic (PBPK) model to predict human plasma concentration-time profiles for 22 highly protein-bound drugs. Tissue distribution was estimated from in vitro drug lipophilicity data, plasma protein binding and the blood: plasma ratio. Clearance was predicted with a well-stirred liver model. Underestimated hepatic clearance for acidic and neutral compounds was corrected by an empirical scaling factor. Predicted values (pharmacokinetic parameters, plasma concentration-time profile) were compared with observed data to evaluate the model accuracy. Of the 22 drugs, less than a 2-fold error was obtained for the terminal elimination half-life (t1/2 , 100% of drugs), peak plasma concentration (Cmax , 100%), area under the plasma concentration-time curve (AUC0-t , 95.4%), clearance (CLh , 95.4%), mean residence time (MRT, 95.4%) and steady state volume (Vss , 90.9%). The impact of fup errors on CLh and Vss prediction was evaluated. Errors in fup resulted in proportional errors in clearance prediction for low-clearance compounds, and in Vss prediction for high-volume neutral drugs. For high-volume basic drugs, errors in fup did not propagate to errors in Vss prediction. This is due to the cancellation of errors in the calculations for tissue partitioning of basic drugs. Overall, plasma profiles were well simulated with the present PBPK model. Copyright © 2016 John Wiley & Sons, Ltd.

Intra-laboratory validated human cell-based in vitro vasculogenesis/angiogenesis test with serum-free medium

Vasculogenesis and angiogenesis are the processes by which new blood vessels are formed. We have developed a serum-free human adipose stromal cell and umbilical cord vein endothelial cell based vasculogenesis/angiogenesis test. In this study, the test was validated in our GLP laboratory following the OECD Guidance Document 34 [1] using erlotinib, acetylic salicylic acid, levamisole, 2-methoxyestradiol, anti-VEGF, methimazole, and D-mannitol to show its reproducibility, repeatability, and predictivity for humans. The results were obtained from immunostained tubule structures and cytotoxicity assessment. The performance of the test was evaluated using 26 suspected teratogens and non-teratogens. The positive predictive value was 71.4% and the negative predictive value was 50.0%, indicating that inhibition of vasculogenesis is a significant mechanism behind teratogenesis. In conclusion, this test has great potential to be a screening test for prioritization purposes of chemicals and to be a test in a battery to predict developmental hazards in a regulatory context.

Pharmacokinetics and Bioavailability of a Fixed-Dose Combination of Ibuprofen and Paracetamol after Intravenous and Oral Administration

Background and Objectives

Previously published studies have suggested the lack of a pharmacokinetic interaction between ibuprofen and paracetamol when they are delivered as a fixed-dose oral combination. The aim of this study was to determine the pharmacokinetic profile and safety of a fixed-dose intravenous (IV) combination, containing 3 mg/mL ibuprofen and 10 mg/mL paracetamol, in comparison with its individual components. The study also assessed the relative bioavailability of the same doses of the active ingredients when they were administered as an oral formulation.

Methods

A single-dose, open-label, randomized, five-period cross-over sequence pharmacokinetic study was undertaken in 30 healthy volunteers. Serial plasma samples were assayed for both paracetamol and ibuprofen concentrations, using validated liquid chromatography–tandem mass spectrometry methods. Pharmacokinetic parameters were computed using standard non-compartmental analyses. Adverse events were also assessed. The ratios of the maximum measured plasma concentration (C_max), the area under the plasma concentration–time curve (AUC) from time zero to the time of the last measurable plasma concentration (AUC_t) and AUC from time zero to infinity (AUC_∞) were analysed for bioequivalence as determined by 90 % confidence intervals.

Results

The pharmacokinetic parameters of ibuprofen and paracetamol were very similar for the combination and monotherapy IV preparations; the ratios of the C_max, AUC_t and AUC_∞ values fell within the 80–125 % acceptable bioequivalence range. Precise dose proportionality for both compounds was also determined for the half dose of the IV formulation in comparison with the full dose. The relative bioavailability of paracetamol (93.78 %) and ibuprofen (96.45 %) confirmed the pharmacokinetic equivalence of the oral and IV formulations of the fixed-dose combination.

Conclusion

Concomitant administration of 3 mg/mL ibuprofen and 10 mg/mL paracetamol in a fixed-dose IV combination does not alter the pharmacokinetic profiles of either drug. The IV and oral dose forms of such a combination are pharmacokinetically equivalent.

Equivalent intraperitoneal doses of ibuprofen supplemented in drinking water or in diet: a behavioral and biochemical assay using antinociceptive and thromboxane inhibitory dose-response curves in mice

Background. Ibuprofen is used chronically in different animal models of inflammation by administration in drinking water or in diet due to its short half-life. Though this practice has been used for years, ibuprofen doses were never assayed against parenteral dose–response curves. This study aims at identifying the equivalent intraperitoneal (i.p.) doses of ibuprofen, when it is administered in drinking water or in diet.

Methods. Bioassays were performed using formalin test and incisional pain model for antinociceptive efficacy and serum TXB₂ for eicosanoid inhibitory activity. The dose–response curve of i.p. administered ibuprofen was constructed for each test using 50, 75, 100 and 200 mg/kg body weight (b.w.). The dose–response curves were constructed of phase 2a of the formalin test (the most sensitive phase to COX inhibitory agents), the area under the ‘change in mechanical threshold’-time curve in the incisional pain model and serum TXB₂ levels. The assayed ibuprofen concentrations administered in drinking water were 0.2, 0.35, 0.6 mg/ml and those administered in diet were 82, 263, 375 mg/kg diet.

Results. The 3 concentrations applied in drinking water lay between 73.6 and 85.5 mg/kg b.w., i.p., in case of the formalin test; between 58.9 and 77.8 mg/kg b.w., i.p., in case of the incisional pain model; and between 71.8 and 125.8 mg/kg b.w., i.p., in case of serum TXB₂ levels. The 3 concentrations administered in diet lay between 67.6 and 83.8 mg/kg b.w., i.p., in case of the formalin test; between 52.7 and 68.6 mg/kg b.w., i.p., in case of the incisional pain model; and between 63.6 and 92.5 mg/kg b.w., i.p., in case of serum TXB₂ levels.

Discussion. The increment in pharmacological effects of different doses of continuously administered ibuprofen in drinking water or diet do not parallel those of i.p. administered ibuprofen. It is therefore difficult to assume the equivalent parenteral daily doses based on mathematical calculations.

Ibuprofen is a non-competitive inhibitor of the peptide transporter hPEPT1 (SLC15A1): possible interactions between hPEPT1 substrates and ibuprofen

BACKGROUND AND PURPOSE

Recently, we identified etodolac as a possible ligand for the human intestinal proton-couple peptide transporter (hPEPT1). This raised the possibility that other non-steroidal anti-inflammatory drugs, and especially ibuprofen, could also interact with hPEPT1. Here, we have assessed the interactions of ibuprofen with hPEPT1.

EXPERIMENTAL APPROACH

The uptake of [(14)C]Gly-Sar, [(3)H]Ibuprofen and other radio-labelled compounds were investigated in Madin-Darby canine kidney cells (MDCK)/hPEPT1, MDCK/Mock, LLC-PK(1) or Caco-2 cells. The transepithelial transport of ibuprofen and hPEPT1 substrates was investigated in Caco-2 cell monolayers.

KEY RESULTS

Ibuprofen concentration dependently inhibited hPEPT1-mediated uptake of Gly-Sar in MDCK/hPEPT1 cells (K(i)(app) = 0.4 mM) but uptake of ibuprofen in Caco-2 cells and MDCK/hPEPT1 cells was not inhibited by hPEPT1 substrates. The maximum uptake rate for Gly-Sar uptake was reduced from 522 pmol·min(-1)·cm(-2) to 181 pmol·min(-1)·cm(-2) and 78 pmol·min(-1)·cm(-2) in the presence of 0.5 mM and 1 mM ibuprofen, respectively. The interaction between ibuprofen and hPEPT1 was thus non-competitive. In LLC-PK1 cells, ibuprofen (1 mM) did not influence the transporter-mediated uptake of glycine or α-methyl-D-glycopyranoside. In Caco-2 cell monolayers the absorptive transport of δ-aminolevulinic acid was reduced by 23% and 48% by ibuprofen (1 and 10 mM), respectively. Likewise the transport of Gly-Sar was reduced by 23% in the presence of ibuprofen (1 mM).

CONCLUSIONS AND IMPLICATIONS

Ibuprofen is a non-competitive inhibitor of hPEPT1. As ibuprofen reduced the transepithelial transport of δ-aminolevulinic acid, drug-drug interactions between ibuprofen and hPEPT1 drug substrates at their site of absorption are possible if administered together.

Management of phosgene-induced acute lung injury

CONTEXT

Phosgene is a substance of immense importance in the chemical industry. Because of its widespread industrial use, there is potential for small-scale exposures within the workplace, large-scale accidental release, or even deliberate release into a built-up area.

OBJECTIVE

This review aims to examine all published studies concerning potential treatments for phosgene-induced acute lung injury and incorporate them into up-to-date clinical guidance. In addition, it aims to contrast the approaches when dealing with small numbers of patients known to be exposed (possibly with dose information) with the presentation of a large and heterogeneous population of casualties following a significant industrial accident or deliberate release; no published guidelines have specifically addressed this second problem.

METHODS

PubMed and Embase were searched for all available years till April 2010 and 584 papers were identified and considered.

EXPERIMENTAL STUDIES

Because of the nature of the injury, there have been no human trials of patients exposed to phosgene. Multiple small and large animal studies have been performed to examine potential treatments of phosgene-induced acute lung injury, but many of these used isolated organ models, pretreatment regimens, or clinically improbable doses. Recent studies in large animals using both realistic time frames and dosing regimens have improved our knowledge, but clinical guidance remains based on incomplete data. Management of a small-scale, confirmed exposure. In the circumstance of a small-scale, confirmed industrial release where a few individuals are exposed and present rapidly, an intravenous bolus of high-dose corticosteroid (e.g., methylprednisolone 1 g) should be considered, although there are no experimental data to support this recommendation. The evidence is that there is no benefit from nebulized steroid even when administered 1 h after exposure, or methylprednisolone if administered intravenously ≥6 h after exposure. Consideration should also be given to administration of nebulized acetylcysteine 1-2 g, though there is no substantive evidence of benefit outside a small animal, isolated lung model and there is a possibility of adverse effects. If the oxygen saturation falls below 94%, patients should receive the lowest concentration of supplemental oxygen to maintain their SaO(2) in the normal range. Once patients require oxygen, nebulized β-agonists [e.g., salbutamol (albuterol) 5 mg by nebulizer every 4 h] may reduce lung inflammation if administered within 1 h of exposure. Elective intubation should be considered early using an ARDSnet protective ventilation strategy. Management of a large-scale, non-confirmed exposure. In the circumstances of a large-scale industrial or urban release, not all patients presenting will have been exposed and health services are likely to be highly stretched. In this situation, patients should not be treated immediately as there is no evidence that delaying therapy causes harm, rather they should be rested and observed with regular physical examination and measurement of peripheral oxygen saturations. Once a patient's oxygen saturation falls below 94%, treatment with the lowest concentration of oxygen required to maintain their oxygen saturations in the normal range should be started. Once oxygen has been started, nebulized β-agonists [e.g., salbutamol (albuterol) 5 mg by nebulizer every 4 h] may reduce lung inflammation if administered within 1 h of exposure, though delayed administration which is likely following a large-scale release has not been tested formally. There is no benefit from nebulized steroid even when administered 1 h after exposure, or high-dose corticosteroid if administered intravenously ≥6 h after exposure. Although there are no experimental data to support this recommendation, an intravenous bolus of high-dose corticosteroid (e.g., methylprednisolone 1 g) may be considered if presentation is <6 h and resources allow. Depending on the numbers of casualties presenting, invasive ventilation should be initiated either electively once symptoms present (especially where there is a short latent period, indicating likelihood of more significant injury), or delayed until required. Ventilation should be with high positive end expiratory pressure, ARDSnet recommended ventilation.

CONCLUSIONS

The mechanisms underlying the phosgene-induced acute lung injury are not well understood. Future experimental work should ensure that potential treatments are tested in a large animal model using realistic dosing regimens and clinically relevant timings, such as those that might be found in a mass casualty situation.

Ibuprofen-induced hypersensitivity syndrome

Ibuprofen is a widely used antipyretic and analgesic nonsteroidal antiinflammatory drug (NSAID). With the aging of the population, there will be a significant increase in the prevalence of painful degenerative and inflammatory rheumatic conditions. This increase likely will lead to a parallel increase in the use of NSAIDs, including ibuprofen. The primary effect of the NSAIDs is to inhibit cyclooxygenase (prostaglandin synthase), thereby impairing the ultimate transformation of arachidonic acid to prostaglandins, prostacyclin, and thromboxanes. Although in the majority of cases it is safe, this NSAID, ibuprofen, can produce an unpredictable, idiosyncratic, type B reaction that may pose a major concern in clinical practice. Type B reactions are known to occur in susceptible individuals. The true hypersensitivity reaction (HSR) is a systemic disease defined by the triad of fever, rash, and internal organ involvement that starts 1 day to 12 weeks after the initiation of therapy. HSR has limited the therapeutic use of many drugs, including ibuprofen. Hypersensitivity syndrome associated with ibuprofen is a host-dependent drug reaction that is idiosyncratic in nature. This reaction likely is caused by a combination of metabolic and immunologic factors. Immune mediated components, such as T-cell and their products cytokines and chemokines, can exacerbate cellular responses and create complex pathways that lead to a variety of clinical manifestations. Our review presents an ibuprofen-induced clinical manifestation of hypersensitivity syndrome and the necessity of wisely monitoring the patients clinically and by laboratory investigations when prescribing this drug.

Bioavailability of ibuprofen following oral administration of standard ibuprofen, sodium ibuprofen or ibuprofen acid incorporating poloxamer in healthy volunteers

Background

The aim of this study was to compare the pharmacokinetic properties of sodium ibuprofen and ibuprofen acid incorporating poloxamer with standard ibuprofen acid tablets.

Methods

Twenty-two healthy volunteers were enrolled into this randomised, single-dose, 3-way crossover, open-label, single-centre, pharmacokinetic study. After 14 hours' fasting, participants received a single dose of 2 × 200 mg ibuprofen acid tablets (standard ibuprofen), 2 × 256 mg ibuprofen sodium dihydrate tablets (sodium ibuprofen; each equivalent to 200 mg ibuprofen acid) and 2 × 200 mg ibuprofen acid incorporating 60 mg poloxamer 407 (ibuprofen/poloxamer). A washout period of 2-7 days separated consecutive dosing days. On each of the 3 treatment days, blood samples were collected post dose for pharmacokinetic analyses and any adverse events recorded. Plasma concentration of ibuprofen was assessed using a liquid chromatographic-mass spectrometry procedure in negative ion mode. A standard statistical ANOVA model, appropriate for bioequivalence studies, was used and ratios of 90% confidence intervals (CIs) were calculated.

Results

T_max for sodium ibuprofen was less than half that of standard ibuprofen (median 35 min vs 90 min, respectively; P = 0.0002) and C_max was significantly higher (41.47 μg/mL vs 31.88 μg/mL; ratio test/reference = 130.06%, 90% CI 118.86-142.32%). Ibuprofen/poloxamer was bioequivalent to the standard ibuprofen formulation, despite its T_max being on average 20 minutes shorter than standard ibuprofen (median 75 mins vs 90 mins, respectively; P = 0.1913), as the ratio of test/reference = 110.48% (CI 100.96-120.89%), which fell within the 80-125% limit of the CPMP and FDA guidelines for bioequivalence. The overall extent of absorption was similar for the three formulations, which were all well tolerated.

Conclusion

In terms of T_max, ibuprofen formulated as a sodium salt was absorbed twice as quickly as from standard ibuprofen acid. The addition of poloxamer to ibuprofen acid did not significantly affect absorption.

Ibuprofen impairs allosterically peroxynitrite isomerization by ferric human serum heme-albumin

Human serum albumin (HSA) participates in heme scavenging; in turn, heme endows HSA with myoglobin-like reactivity and spectroscopic properties. Here, the allosteric effect of ibuprofen on peroxynitrite isomerization to NO(3)(-) catalyzed by ferric human serum heme-albumin (HSA-heme-Fe(III)) is reported. Data were obtained at 22.0 degrees C. HSA-heme-Fe(III) catalyzes peroxynitrite isomerization in the absence and presence of CO(2); the values of the second order catalytic rate constant (k(on)) are 4.1 x 10(5) and 4.5 x 10(5) m(-1) s(-1), respectively. Moreover, HSA-heme-Fe(III) prevents peroxynitrite-mediated nitration of free added l-tyrosine. The pH dependence of k(on) (pK(a) = 6.9) suggests that peroxynitrous acid reacts preferentially with the heme-Fe(III) atom, in the absence and presence of CO(2). The HSA-heme-Fe(III)-catalyzed isomerization of peroxynitrite has been ascribed to the reactive pentacoordinated heme-Fe(III) atom. In the absence and presence of CO(2), ibuprofen impairs dose-dependently peroxynitrite isomerization by HSA-heme-Fe(III) and facilitates the nitration of free added l-tyrosine; the value of the dissociation equilibrium constant for ibuprofen binding to HSA-heme-Fe(III) (L) ranges between 7.7 x 10(-4) and 9.7 x 10(-4) m. Under conditions where [ibuprofen] is >>L, the kinetics of HSA-heme-Fe(III)-catalyzed isomerization of peroxynitrite is superimposable to that obtained in the absence of HSA-heme-Fe(III) or in the presence of non-catalytic HSA-heme-Fe(III)-cyanide complex and HSA. Ibuprofen binding impairs allosterically peroxynitrite isomerization by HSA-heme-Fe(III), inducing the hexacoordination of the heme-Fe(III) atom. These results represent the first evidence for peroxynitrite isomerization by HSA-heme-Fe(III), highlighting the allosteric modulation of HSA-heme-Fe(III) reactivity by heterotropic interaction(s), and outlining the role of drugs in modulating HSA functions. The present results could be relevant for the drug-dependent protective role of HSA-heme-Fe(III) in vivo.

Topical ocular delivery of NSAIDs

In ocular tissue, arachidonic acid is metabolized by cyclooxygenase to prostaglandins which are the most important lipid derived mediators of inflammation. Presently nonsteroidal anti-inflammatory drugs (NSAIDs) which are cyclooxygenase (COX) inhibitors are being used for the treatment of inflammatory disorders. NSAIDs used in ophthalmology, topically, are salicylic-, indole acetic-, aryl acetic-, aryl propionic- and enolic acid derivatives. NSAIDs are weak acids with pKa mostly between 3.5 and 4.5, and are poorly soluble in water. Aqueous ophthalmic solutions of NSAIDs have been made using sodium, potassium, tromethamine and lysine salts or complexing with cyclodextrins/solubilizer. Ocular penetration of NSAID demands an acidic ophthalmic solution where cyclodextrin could prevent precipitation of drug and minimize its ocular irritation potential. The incompatibility of NSAID with benzalkonium chloride is avoided by using polysorbate 80, cyclodextrins or tromethamine. Lysine salts and alpha-tocopheryl polyethylene glycol succinate disrupt corneal integrity, and their use requires caution. Thus a nonirritating ophthalmic solution of NSAID could be formulated by dissolving an appropriate water-soluble salt, in the presence of cyclodextrin or tromethamine (if needed) in mildly acidified purified water (if stability permits) with or without benzalkonium chloride and polyvinyl alcohol. Amide prodrugs met with mixed success due to incomplete intraocular hydrolysis. Suspension and ocular inserts appear irritating to the inflamed eye. Oil drop may be a suitable option for insoluble drugs and ointment may be used for sustained effect. Recent studies showed that the use of colloidal nanoparticle formulations and the potent COX 2 inhibitor bromfenac may enhance NSAID efficacy in eye preparations.

Follicular penetration of topically applied caffeine via a shampoo formulation

AIMS

Follicular drug delivery is the prerequisite for an effective treatment of androgenetic alopecia or other reasons of premature hair loss.

METHODS

The follicular penetration of caffeine, applied topically in a shampoo formulation for 2 min, was measured with highly sensitive surface ionization in combination with mass spectroscopy, a selective method for the detection of very small quantities of transcutaneously absorbed substances in the blood. An experimental protocol, developed to selectively block the follicular pathway within the test area, was used. Based on this principle, a clear distinction between interfollicular and follicular penetration of topically applied caffeine was feasible.

RESULTS

After 2 min, caffeine penetrated via the hair follicles and stratum corneum.

CONCLUSION

It was found that the penetration via hair follicles was faster and higher compared with the interfollicular route and that hair follicles are the only pathway for fast caffeine absorption during the first 20 min after application.

Computational prediction of oral drug absorption based on absorption rate constants in humans

Models for predicting oral drug absorption kinetics were developed by correlating absorption rate constants in humans (K(a)) with computational molecular descriptors. The K(a) values of a set of 22 passively absorbed drugs were derived from human plasma time-concentration profiles using a deconvolution approach. The K(a) values correlated well with experimental values of fraction of dose absorbed in humans (FA), better than the values of human jejunal permeability (P(eff)) which have previously been used to assess the in vivo absorption kinetics of drugs. The relationships between the K(a) values of the 22 structurally diverse drugs and computational molecular descriptors were established with PLS analysis. The analysis showed that the most important parameters describing log K(a) were polar surface area (PSA), number of hydrogen bond donors (HBD), and log D at a physiologically relevant pH. Combining log D at pH 6.0 with PSA or HBD resulted in models with Q(2) and R(2) values ranging from 0.74 to 0.76. An external data set of 169 compounds demonstrated that the models were able to predict K(a) values that correlated well with experimental FA values. Thus, it was shown that, using a combination of only two computational molecular descriptors, it is possible to predict with good accuracy the K(a) value for a new drug candidate.

Classification of orally administered drugs on the World Health Organization Model list of Essential Medicines according to the biopharmaceutics classification system

Since its inception in 1995, the biopharmaceutical classification system (BCS) has become an increasingly important tool for regulation of drug products world-wide. Until now, application of the BCS has been partially hindered by the lack of a freely available and accurate database summarising solubility and permeability characteristics of drug substances. In this report, orally administered drugs on the Model list of Essential Medicines of the World Health Organization (WHO) are assigned BCS classifications on the basis of data available in the public domain. Of the 130 orally administered drugs on the WHO list, 61 could be classified with certainty. Twenty-one (84%) of these belong to class I (highly soluble, highly permeable), 10 (17%) to class II (poorly soluble, highly permeable), 24 (39%) to class III (highly soluble, poorly permeable) and 6 (10%) to class IV (poorly soluble, poorly permeable). A further 28 drugs could be provisionally assigned, while for 41 drugs insufficient or conflicting data precluded assignment to a specific BCS class. A total of 32 class I drugs (either certain or provisional classification) were identified. These drugs can be further considered for biowaiver status (drug product approval based on dissolution tests rather than bioequivalence studies in humans).

Comparison of different ibuprofen-amino acid compounds with respect to emulsifying and cytotoxic properties

Sodium ibuprofen (Ibu-Na) and different ibuprofen-amino acid compounds, lysinate (Ibu-Lys), arginate (Ibu-Arg) and histidinate (Ibu-His), were evaluated for emulsifying, haemolytic and cytotoxic properties. The highest reduction of surface tension was obtained with Ibu-Lys which shows good emulsifying qualities. At the same time, Ibu-Lys reveals the highest haemolytic activity and affects porcine cornea integrity. However, incorporation of Ibu-Lys into an emulsion system significantly decreases haemolysis. On the contrary Ibu-Arg, which shows a lower surface tension reduction, allows, unlike Ibu-Na and Ibu-His, for comparably stable emulsions with comparable erythrocyte damage.

Post-iontophoresis transport of ibuprofen lysine across rabbit ear skin

The aim of this work was to study in vitro the post-iontophoresis transport of ibuprofen lysine across rabbit ear skin, from ibuprofen lysine water solutions (20-200 mg/ml and pH 6.8-7.8). Current densities of 0.125, 0.25, and 0.5 mA/cm(2) were applied either continuously or for 15, 30, and 60 min followed by passive diffusion for up to 5h. The results showed a significantly higher cathodal transport compared to passive flux. Anodal iontophoresis also increased ibuprofen permeation, even though the drug is negatively charged. The application of an electric current for a limited period of time, followed by passive diffusion from the reservoir in contact with the skin, produced much higher post-iontophoresis fluxes of ibuprofen than passive diffusion. Post-iontophoresis transport of ibuprofen from lysine salt solutions linearly depended on the total amount of current applied during iontophoresis, and in the absence of background ions was independent of donor drug concentration. The reason for this behavior was the creation of a drug reservoir in the skin owing to the short period of current application.

Pharmacokinetics of oral ibuprofen in premature infants

Patent ductus arteriosus (PDA) is a frequent complication in premature infants. So far, intravenous indomethacin is the standard mode of medical therapy in such patients but carries a risk of frequently occurring side effects. Ibuprofen, another nonsteroidal anti-inflammatory drug, has also been shown to be efficacious in closing ductus with lesser adverse effects after parenteral administration. However, limited data are available on the pharmacokinetics of intravenous ibuprofen in this population. Nonavailability of parenteral preparation and lack of information regarding pharmacokinetic disposition of ibuprofen in this subgroup of the population led the authors to conduct this pharmacokinetic study with oral ibuprofen. Twenty premature infants with a gestational age of 30.45 +/- 0.33 weeks and a birth weight of 1262.5 +/- 55.4 g (values given as mean +/- SEM) admitted to the neonatal unit were enrolled in this study. Ibuprofen was administered in a single oral dose of 10 mg/kg between 4 and 72 hours postnatally, and blood samples were collected through an indwelling vascular catheter at time 0 and 1, 2, 4, 8, 12, and 24 hours. Ibuprofen plasma concentrations were assayed by high-performance liquid chromatography. There was a large interindividual variability observed for plasma concentrations, elimination half-life (t1/2) (15.72 +/- 3.76 h), and area under the plasma concentration-time curve (AUC0-infinity) (402.60 +/- 79.67 micrograms.h/mL) in these babies. Variables such as gestational age, birth weight, and sex did not affect ibuprofen pharmacokinetics significantly (p > 0.05). Moreover, no correlation could be found between elimination half-life and gestational age (r = 0.02). Ibuprofen pharmacokinetics showed a wide variability in premature infants. The results of the present study warrant revising the oral dosage schedule to achieve comparable plasma concentrations of ibuprofen associated with successful closure of ductus, as reported in earlier studies.

Simultaneous fitting of R- and S-ibuprofen plasma concentrations after oral administration of the racemate

AIMS

To assess the pharmacokinetic equivalence of two different formulations of ibuprofen lysinate with special focus on the expected effects.

METHODS

Sixteen healthy volunteers received cross-over ibuprofen lysinate as either one tablet of 400 mg ('test') or two tablets of 200 mg ('reference'). Ibuprofen plasma concentrations were followed up for 10 h. Bioequivalence was assessed by standard noncompartmental methods. Ibuprofen plasma concentrations were fitted with a model that took bioinversion of R- to S-ibuprofen into account.

RESULTS

Peak plasma concentrations of R- and S-ibuprofen were 18.1 and 20 microg ml(-1) (test), and 18.2 and 20 microg ml(-1) (reference). Areas under the plasma concentration vs. time curves were 39.7 and 67.5 microg ml(-1) h (test), and 41.1 and 68.2 microg ml(-1) h (reference). Clearance of R-ibuprofen was 5.2 (test) and 5 l h(-1) (reference). A specific plasma concentration was reached with the test formulation about 5 min later than with the reference. Parameters from compartmental modelling were (given for R-and then for S-ibuprofen): body clearance: 4.9 and 4.64 l h(-1), central volume of distribution: 2.8 and 4.1 l, intercompartment clearance: 5.1 and 5.45 l h(-1), peripheral volume of distribution: 4.1 and 5.2 l. The absorption rate constant was 1.52 h(-1), and the test but not the reference formulation had a lag time of 0.1 h. Simulations showed similarity between formulations of the expected effects except for a calculated delay of 6 min with the test formulation.

CONCLUSIONS

Ibuprofen formulations were bioequivalent. The pharmacokinetic model may serve as a basis for future pharmacokinetic/pharmacodynamic calculations after administration of racemic ibuprofen.

Phosgene exposure: mechanisms of injury and treatment strategies

Phosgene (carbonyl chloride, CAS 75-44-5) is a highly reactive gas of historical interest and current industrial importance. Phosgene has also proved to be a useful model for the study of those biochemical mechanisms that lead to permeability-type pulmonary edema (adult respiratory distress syndrome). In turn, the study of phosgene-induced adult respiratory distress syndrome has provided insights leading to revised treatment strategies for exposure victims. We summarized recent findings on the mechanisms of phosgene-induced pulmonary edema and their implications for victim management. In light of that research, we also provide a comprehensive approach to the management and treatment of phosgene exposure victims.

Pharmacokinetics and protein binding of intravenous ibuprofen in the premature newborn infant

The elimination, disposition and protein binding of ibuprofen (IBU) in premature infants were studied for use in the prevention of intraventricular hemorrhage and closure of patent ductus arteriosus. The kinetic profile of i.v. IBU lysine (10 mg/kg bolus) given within the first 3 h after birth was studied in 21 premature neonates (mean birthweight = 944.7 g, range: 575-1450 g; gestational age: 26.8 weeks, range: 22-31 weeks). Blood samples (0.3 ml/sample) were obtained at time 0 and at 1, 3, 6, 12, 24, 48, and 72 h post-dose for IBU by high-performance liquid chromatography (HPLC). Kinetic analyses assumed applicability of one open-compartment model and calculations from the model-independent areas under the time concentration curve (AUC). Data (mean +/- SEM) show that apparent volume of distribution (AVd) was 62.1 +/- 3.9 ml/kg, plasma t1/2 beta was 30.5 +/- 4.2 h, elimination rate constant (Kel) was 0.032 +/- 0.004 h-1, plasma clearance was 2.06 +/- 0.33 ml/kg/h and plasma concentration (Cp) at 1 h was 180.6 +/- 11.1 mg/l. Gestational age and birthweight were not related to drug elimination. In 10 neonates, IBU maintenance dose of 5 mg/kg once daily on days 2 and 3 generated mean Cp of 116.6 +/- 54.5 mg/l and 113.6 +/- 58.2 mg/l, respectively. Protein binding by ultrafiltration and capillary electrophoresis showed that the percentage bound IBU was significantly lower in full term cord plasma (94.98 +/- 0.39%, n = 26) compared to adult plasma protein (mean +/- SE = 98.73 +/- 0.31%, n = 8, p < 0.0001). Compared to data from adults and older children, IBU elimination is markedly prolonged in neonates and protein binding is slightly lower. Thus, investigational and clinical therapeutic regimens should be adjusted to account for decreased drug disposition to ensure safe and effective therapy.

Pharmacokinetics and bioinversion of ibuprofen enantiomers in humans

An open, randomized, six-way crossover study was conducted in 12 healthy males to assess pharmacokinetics and bioinversion of ibuprofen enantiomers. The mean plasma terminal half-life (t1/2) of R(-)ibuprofen was 1.74 hr when intravenously infused as a racemic mixture and was 1.84 hr when intravenously infused alone. The mean t1/2 of S(+)ibuprofen was 1.77 hr when dosed as S(+)ibuprofen. Examination of values of both the absorption and disposition parameters of R(-)ibuprofen revealed that the kinetics of R(-)ibuprofen were not altered by concurrent administration of S(+)ibuprofen. In this study, there was little or no presystemic inversion of R(-)ibuprofen to its S(+)isomer. Also, 69% of the intravenous dose of R(-)ibuprofen was systemically inverted and 57.6% of the oral dose of R(-)ibuprofen lysinate was bioavailable as S(+)ibuprofen. These results indicate that the bioinversion of R(-)ibuprofen administered orally is mainly systemic. Because bioinversion of R(-)ibuprofen is not complete, S(+)ibuprofen produced higher bioavailability of S(+)ibuprofen (92.0%) than either racemic ibuprofen (70.7%) or R(-)ibuprofen (57.6%). However, bioavailability of R(-)ibuprofen (83.6%) when dosed alone was not significantly different from when dosed as racemic mixture (80.7%).

Bioavailability of racemic ibuprofen and its lysinate from suppositories in rabbits

Plasma concentration (C)-time (t) plots of ibuprofen from suppositories in rabbits are characterized by the sum of two exponentials, C = Be-lambda 2t-Ae-lambda 1t. When A exceeds B, there is a lag time (tlag = tc = 0) before the start of absorption. Evidence for dose-dependent area under the curve (AUC) of C versus t values is presented with the implication that elimination rate constants (ke) decrease and the AUC/dose ratio increase with dose. The lack of significant differences between the AUC values from suppository and the intravenous studies with similar doses implies complete absorption of ibuprofen from all the suppositories studied. The absorption rate constants (ka) were estimated on the presumption of complete absorption and dose-dependent elimination. Ibuprofen lysinate was absorbed significantly more readily than the free acid from suppositories. The lysinate suppository with a lipophilic surfactant had a higher absorption rate constant than that with a hydrophilic surfactant. The ka values did not significantly differ for a twofold difference in dose. Equations were developed to calculate true AUC and area under the moment curve (AUMC) values when A exceeds B, and to transform C versus t plots to the origin with A' = A = B. Times of maximum peak heights, mean residence (MRT), and mean absorption times (MAT = 1/ka) of suppositories when A > B are shown to differ by the lag time (tc = 0) from the plots of C versus t transposed to the origin. Although corrected AUC values when A > B are equal to the AUC values of C versus t plots transposed to the origin (A' = A = B), the corrected AUMC values when A > B significantly differ from the AUMC values for the C versus t plots transposed to the origin.