Impact of immunogenicity on pharmacokinetics, efficacy and safety of adalimumab in adult patients with moderate to severe chronic plaque psoriasis.

BACKGROUND: Adalimumab is a tumour necrosis factor-alpha antibody approved for treatment of moderate to severe chronic plaque psoriasis. OBJECTIVE: To characterise population pharmacokinetics of adalimumab 40 mg every other week dosing regimen and impact of immunogenicity on pharmacokinetics, efficacy and safety in psoriasis patients. METHODS: Patients were enrolled in a Phase 3 study comprising a 16-week double-blind, placebo-controlled period, a 17-week open-label period for Week 16 Psoriasis Area and Severity Index (PASI) 75 responders, and a 19-week double-blind, placebo-controlled period for Week 33 PASI 75 responders. Serum adalimumab and anti-adalimumab antibody (AAA) concentrations were measured and a population pharmacokinetic model devleoped to identify patient/disease factors affecting adalimumab pharmacokinetics. Impact of immunogenicity on treatment efficacy and safety was also assessed. RESULTS: Week 33 mean adalimumab concentration was 5.2 µg/mL. Week 16 responders had higher adalimumab concentrations than non-responders (6.3 vs. 2.2 µg/mL). Bodyweight and study were significant covariates in population pharmacokinetic model with weight accounting for 19% and 29% of variability in adalimumab clearance and volume of distribution, respectively. A total of 8.8% of adalimumab-treated patients tested AAA positive and had twofold higher adalimumab clearance. PASI 75 response rate was comparable between AAA+ and AAA- patients at Weeks 33 and 52 (Week 33: 36% vs. 22.5%, Week 52: 21.1% vs. 17.8%) and adverse events incidence was similar between the two groups. CONCLUSIONS: Patient weight and study significantly affect adalimumab clearance and volume of distribution in psoriasis patients. Development of AAAs result in lower adalimumab exposure and efficacy with no effect on adverse events incidence.

Pharmacokinetics and tolerability of paritaprevir, a direct acting antiviral agent for hepatitis C virus treatment, with and without ritonavir in healthy volunteers.

AIMS: Paritaprevir is a direct acting antiviral agent for use as part of a multidrug hepatitis C virus infection treatment regimen. To characterize the pharmacokinetics, safety, and tolerability of paritaprevir and determine an optimal dosing regimen for subsequent evaluations, clinical studies were conducted with paritaprevir alone or with ritonavir, a cytochrome P450 3A4 inhibitor anticipated to increase paritaprevir exposure. METHODS: Two phase 1, double-blind, placebo-controlled, parallel group studies were conducted in healthy volunteers (NCT00850044 and NCT00931281). Single dose study participants (n = 87) were randomized to one time administration of either paritaprevir or placebo, or paritaprevir with ritonavir or placebo. Participants (n = 38) enrolled in the multiple dose study received paritaprevir with ritonavir or placebo once or twice daily for 14 days. Pharmacokinetics, safety and tolerability were assessed throughout the study treatment periods. RESULTS: After single or multiple dose administration, paritaprevir displayed non-linear pharmacokinetics, with maximum plasma concentration and area under the plasma concentration-time curve increasing in a greater than dose proportional manner. Concomitant administration of 100 mg ritonavir increased paritaprevir exposure from a 300 mg dose approximately 30- to 50-fold and extended paritaprevir half-life. The tolerability of paritaprevir was similar with or without ritonavir. Asymptomatic, transient increases in bilirubin were observed but were not associated with abnormalities in other liver function tests. CONCLUSIONS: Paritaprevir exhibits non-linear pharmacokinetics with greater than dose proportional increases in exposure after single or multiple dosing. Co-administration with ritonavir increases paritaprevir exposure and half-life without adversely influencing tolerability.

Pharmacokinetics and dose recommendations for cyclosporine and tacrolimus when coadministered with ABT-450, ombitasvir, and dasabuvir.

ABT-450, ombitasvir, and dasabuvir are direct-acting antiviral agents (DAAs) that have been developed for combination treatment of chronic hepatitis C virus (HCV) infection. Because these DAAs have metabolic and transporter profiles that overlap with cyclosporine and tacrolimus disposition, there is potential for drug interactions. Two Phase 1 studies assessed effects of ABT-450 (150 mg coadministered with ritonavir 100 mg once daily), ombitasvir (25 mg once daily), and dasabuvir (400 mg twice daily) on the pharmacokinetics, safety, and tolerability of a single dose of cyclosporine (30 mg) or tacrolimus (2 mg) in healthy volunteers (N = 12 per study). In the presence of steady-state concentrations of all 3 DAAs, dose-normalized cyclosporine concentration at 24 hours (C24), and area under the concentration-time curve from time 0 to infinity (AUC(∞)) were 15.8-fold and 5.8-fold, respectively, and dose-normalized tacrolimus C24 and AUC(∞) were 17-fold and 57-fold, respectively, of either agent alone. Cyclosporine and tacrolimus half-lives increased from 7 to 25 h and 32 to 232 h, respectively. There were no major safety or tolerability issues in these studies. The results suggest that cyclosporine and tacrolimus doses and dosing frequency should be reduced in HCV-infected posttransplant patients being treated with this 3-DAA regimen.

Population pharmacokinetics of ABT-594 in subjects with diabetic peripheral neuropathic pain.

WHAT IS KNOWN AND OBJECTIVE: ABT-594 is a non-opioid, non-NSAID analgesic. The objective of this work was to characterize the population pharmacokinetics of ABT-594 in subjects with neuropathic pain. METHODS: Efficacy, safety and pharmacokinetics of ABT-594 in subjects with painful diabetic polyneuropathy were evaluated in a randomized, double-blind, placebo-controlled, parallel-group, multi-centre, 7-week Phase 2 study. Subjects (N=266) were approximately equally divided into four groups to receive BID regimens of placebo or 150, 225 and 300 µg of ABT-594. ABT-594 concentrations were determined from all subjects, whereas a subset of subjects provided intensive pharmacokinetic samples on two occasions. One- and two-compartment models were explored for characterizing plasma ABT-594 concentration-time profiles. The relative importance of covariates (age, weight, body surface area, creatinine clearance, gender, nicotine use and albumin concentrations) was examined by use of the likelihood ratio test. Model building was accomplished using stepwise forward selection (P<0·05) and backward elimination (P<0·005) of covariates. Population analyses were performed using NONMEM. RESULTS AND DISCUSSION: Optimal characterization of the plasma concentration data was achieved using a one-compartment base model. Creatinine clearance and age were found to be significant covariates in the forward selection process; backward elimination process identified only creatinine clearance as a significant covariate. WHAT IS NEW AND CONCLUSION: A population pharmacokinetic model was developed to characterize ABT-594 concentrations in subjects with neuropathic pain. As ABT-594 is primarily eliminated as unchanged drug in the urine, creatinine clearance and age were significant covariates of clearance with creatinine clearance being the optimal predictor of ABT-594 clearance.

Long-term cyclosporine pharmacokinetic changes in renal transplant recipients: effects of binding and metabolism.

Sequential changes in the pharmacokinetics of cyclosporine (CsA) and metabolites M1, M17, and M21 were determined, 1, 3, and 12 weeks after initiation of CsA therapy in 21 renal transplant recipients. Concentrations of CsA and its metabolites were measured by HPLC. The dose-adjusted AUC (AUCSS tau) and 24-hour trough (C24trough) level of CsA and the metabolites increased significantly during the study period. However, there was no change in the AUCSS tau ratio of each of the metabolites to that of CsA, suggesting that CsA metabolism did not change. However, the factors that alter the binding and distribution of CsA (i.e., hematocrit, plasma proteins, and lipoproteins) showed a significant rise during the study period, and the rise correlated well with the observed changes in AUCSS tau and C24trough. Thus alterations in the distribution and binding of CsA and its metabolites in blood, rather than reduction in the metabolism of CsA, may explain changes in CsA pharmacokinetics over time.

Pharmacokinetics and pharmacodynamics of single and multiple oral doses of a novel 5-lipoxygenase inhibitor (ABT-761) in healthy volunteers.

OBJECTIVE: This study evaluated the safety, pharmacokinetics and pharmacodynamics of ABT-761 [R(+)-N-[3-[5-(4-fluorophenylmethyl)-2-thienyl]-1- methyl-2-propynyl]-N-hydroxyurea], a new N-hydroxyurea analog. METHODS: This was a randomized, double-blind, placebo-controlled, single- and multiple-dose (15-day) study of ABT-761 (50 to 200 mg/day) in healthy, nonsmoking adult male volunteers. The pharmacokinetics were evaluated by investigation of the time- and dose-dependent effects of ABT-761, and the pharmacologic selectivity of ABT-761 was evaluated based on calcium ionophore-stimulated leukotriene B4 (LTB4) and thromboxane B2 (TXB2) biosynthesis ex vivo in whole blood. RESULTS: After single and multiple doses, mean observed time to reach maximum concentration values of ABT-761 ranged from 4.0 to 7.5 hours. Mean values for maximum concentration and area under the plasma concentration-time curve from 0 to 24 hours increased approximately linearly with dose. Mean terminal half-life and apparent volume of distribution during the terminal elimination phase of ABT-761 ranged from 15.4 to 17.8 hours and 69.5 to 78.9 L, respectively, and was dose independent. Steady state was reached on day 11 after multiple dosing. Less than 0.05% of unchanged ABT-761 was recovered in urine within the 24-hour period after day 15 dosing. Population ABT-761 plasma concentration at which 50% of the maximum possible inhibition was observed for LTB4 inhibition was 0.24 microgram/ml. No differences in mean TXB2 inhibition were observed between the subjects receiving ABT-761 and placebo. CONCLUSIONS: These results indicate that ABT-761 is a potent and selective inhibitor of 5-lipoxygenase and the pharmacokinetics of ABT-761 are time and dose independent between 50 and 200 mg/day after single and multiple dosing.

Effects of divalproex sodium on amitriptyline and nortriptyline pharmacokinetics.

BACKGROUND: Divalproex sodium has been found to be efficacious in the prophylaxis of migraine headaches and the management of the manic phase of bipolar syndrome. Because amitriptyline is also prescribed in these patient populations, data are needed on their potential for interaction. METHODS: The effect of concomitant administration of divalproex sodium on the pharmacokinetics of amitriptyline and its active metabolite, nortriptyline, was investigated in an open-label, sequential, two-period phase I study. Ten healthy male and five healthy female subjects received 50 mg amitriptyline hydrochloride on two occasions: (1) alone (period 1) and (2) 2 hours after receiving the ninth dose of 500 mg divalproex sodium (Depakote) administered once every 12 hours (period 2). RESULTS: Amitriptyline area under the curve was increased 31% from the combined effect of decreased first-pass metabolism and inhibition of systemic metabolism. The elevated nortriptyline plasma levels reflected primarily the increase in amitriptyline concentrations but also appeared to involve modest inhibition of nortriptyline elimination. For the sum of amitriptyline and nortriptyline concentrations, the peak plasma concentration mean was 19% higher with concomitant divalproex dosing. The mean area under the curve for the sum of amitriptyline and nortriptyline concentrations was 42% higher with concomitant divalproex dosing than it was for dosing with amitriptyline alone. CONCLUSION: These results suggested that a lower dose of amitriptyline might be considered when divalproex is administered concomitantly.

The effect of zileuton on antipyrine and indocyanine green disposition.

The effects of single and multiple oral doses of zileuton on the pharmacokinetics of antipyrine and indocyanine green were studied in 16 healthy, nonsmoking adult men by means of a double-blind, randomized, parallel placebo-controlled design. Indocyanine green disposition was not significantly altered by zileuton. Plasma antipyrine clearance declined by 20% (p < 0.0005) and 52% (p < 0.0005) after single and multiple dose zileuton exposure, respectively. Total urinary recovery of unchanged antipyrine and metabolites decreased with zileuton exposure. Selective declines from baseline of 16% (p = 0.007) and 20% (p = 0.003) after single-dose zileuton and 30% (p < 0.0005) and 43% (p < 0.0005) after multiple-dose zileuton were detected in recovery of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine, respectively. Urinary recovery of the N-demethylantipyrine metabolite norantipyrine and percent of conjugation of 3-hydroxymethylantipyrine were unchanged by zileuton. In conclusion, zileuton therapy has no detectable effect on indocyanine green disposition but exerts marked effects on antipyrine plasma and urine metabolite disposition.

Pharmacokinetics and pharmacodynamics of codeine in end-stage renal disease.

The pharmacokinetics and pharmacodynamics of codeine and its metabolites codeine glucuronide, morphine, and morphine glucuronide were assessed after the administration of a single 60 mg oral dose of codeine sulfate and a single 60 mg intravenous dose of codeine phosphate in six healthy volunteers and six patients on chronic hemodialysis. Plasma and urine drug and metabolite concentrations were determined by sensitive and specific RIA procedures. Pharmacodynamics were assessed by pupillometry and vital sign determinations. Codeine elimination half-life and mean residence time were increased significantly in the hemodialysis group (18.69 +/- 9.03 hours and 12.77 +/- 7.09 hours, mean +/- SD, respectively) compared with the healthy volunteer group (4.04 +/- 0.60 hours and 3.90 +/- 0.52 hours, respectively). The total body clearance and volume of distribution of codeine were not significantly different between groups. Peak concentrations, times to peak concentrations, and AUCs for the three metabolites were also not significantly different between the groups, in part as a result of significant interpatient variability in the hemodialysis group. Examination of pupillometry and vital sign data did not reveal clinically significant differences in pharmacodynamics between the groups. Adjustment of dosage regimen may be required in some patients with uremia receiving multiple-dose codeine therapy.

Pharmacokinetics of ciprofloxacin in acutely ill and convalescent elderly patients.

The pharmacokinetics of ciprofloxacin were evaluated in 13 elderly patients with serious infections who were receiving 750 mg orally every 12 hours. The acute evaluations were performed within 24 hours of admission (n = 13), whereas the convalescent evaluations were performed at the end of therapy (n = 7). Serum and urine concentrations of ciprofloxacin were measured using high-performance liquid chromatography. Peak serum concentration (Cmax), terminal elimination half-life (t1/2 beta), apparent total body clearance (CL/f), and apparent volume of distribution (Vd/f) of ciprofloxacin were 5.97 +/- 2.95 mg/liter, 5.31 +/- 2.00 hours, 8.12 +/- 3.83 ml/kg/minute, and 3.63 +/- 1.91 liters/kg during the period of acute illness. Cmax and Vd/f values were moderately increased during the convalescent phase (8.56 +/- 3.43 mg/liter versus 5.87 +/- 2.25 mg/liter, p = 0.138, and 5.95 +/- 3.23 liters/kg versus 3.46 +/- 1.40 liters/kg, 0.05 less than p less than 0.1). The CL/f and t1/2 beta (four to 12 hours) values, however, were not significantly altered. The observed pharmacokinetic characteristics, which are consistent with those derived from single-dose studies in healthy elderly subjects, are markedly different from previous observations in young adult volunteers. However, acute illness does not alter the pharmacokinetics of ciprofloxacin in the elderly. Dosage alterations because of the presence of acute illness in the elderly do not appear to be warranted.

The relationship between cyclosporine pharmacokinetic parameters and subsequent acute rejection in renal transplant recipients.

The best approach to determining the optimal dose of cyclosporine in renal transplant recipients is unclear. In this prospective investigation, CsA pharmacokinetic studies were performed in 45 patients 1, 4, and 12 weeks after the initiation of CsA. Data from 104 studies were then combined to analyze the relationship between CsA kinetic parameters and posttransplant clinical events. Random trough levels, used in the day-to-day adjustment of CsA dose, were examined separately in 19 of the 45 study patients. All CsA levels were measured with high-performance liquid chromatography. Results showed: (1) trough CsA levels, obtained by random sampling, or from the kinetic studies, correlated poorly with dose; however, there was a good correlation between CsA dose and maximum concentration (Cmax, r = .39, P less than .001), area under the concentration-time curve (AUC, r = .45, P less than .001), and terminal elimination half-life (r = .43, P less than .001); (2) several pharmacokinetic parameters correlated with subsequent rejection episodes; patients with acute rejection within 2 or 4 weeks after study had 15-31% lower Cmax (P less than .05) and 13-19% lower AUC (P less than .05) compared to those who were rejection-free; and (3) levels of blood constituents known to bind CsA also correlated with rejection, and this correlation was independent of the impact of kinetic parameters on rejection. Altogether, these results suggested that a limited number of CsA pharmacokinetic studies may be more useful than multiple, random trough levels in monitoring CsA therapy.

Effects of cyclosporine on the isolated perfused rat kidney.

Although cyclosporine (CsA) has been shown to cause decreased renal function in humans, the mechanisms important in cyclosporine nephrotoxicity are not well understood. Investigations of cyclosporine nephrotoxicity in animal models have been complicated by systemic toxic effects not seen in humans. In the present study, the direct renal effects of cyclosporine were investigated in the isolated perfused rat kidney (IPRK) model. Cyclosporine delivered by nontoxic liposomes had no effect on IPRK resistance, perfusate flow, inulin clearance, or fractional reabsorption of sodium, despite marked tissue accumulation of CsA (55.1 +/- 7.2 micrograms/g kidney tissue). In contrast, a 63% decrease in inulin clearance was observed following the administration of intravenous cyclosporine (0.1 ml). However, similar changes in IPRK function were seen after the administration of 0.1 ml of the intravenous cyclosporine vehicle, cremophor, suggesting that the alterations in function were secondary to the vehicle. All together, these findings suggest that cyclosporine nephrotoxicity may be secondary to renal innervation, toxic metabolites, or other systemic effects of cyclosporine not present in the IPRK.

Pharmacodynamic monitoring of cyclosporin.

The efficacy of cyclosporin as an immunosuppressive agent is largely based on clinical indicators such as graft survival, rejection or nephrotoxicity. Therapeutic monitoring is necessary to evaluate the efficacy of cyclosporin therapy. The most widely used method for monitoring cyclosporin therapy is the measurement of predose through blood concentrations of the drug. The relationship of a single or multiple blood cyclosporin concentration to slowly evolving outcomes is difficult to establish. Some investigators have found a good correlation between cyclosporin trough concentrations on the one hand and cyclosporin toxicity and rejection on the other, but others have not. Therapeutic monitoring of cyclosporin may be enhanced using some biological assays for immunosuppression (pharmacodynamic monitoring) in addition to cyclosporin trough concentrations (pharmacokinetic monitoring). However, direct monitoring of the immune response to cyclosporin therapy using a clinically applicable biological assay is difficult. Some pharmacodynamic parameters have been suggested as biological markers in the clinical monitoring of cyclosporin.

Quantifying hepatic function in the presence of liver disease with phenazone (antipyrine) and its metabolites.

The disposition of phenazone (antipyrine), a low extraction compound with low protein binding, is known to be altered in the presence of various types of hepatic dysfunction. As such, its pharmacokinetics may be useful in the objective characterisation of altered liver function. Understanding the known effects of various liver disease states upon the disposition of this probe may provide insight into future applications. This article provides a review of background information about normal plasma phenazone pharmacokinetics, urinary metabolite disposition and tabulations of reported total body clearances of the drug in the presence of cirrhosis, fatty liver, hepatitis and cholestasis in humans. An estimate is made of the sensitivity and specificity of phenazone testing for the verification of the presence of cirrhosis based on this compiled literature.

Pharmacokinetics and pharmacodynamics of zileuton after oral administration of single and multiple dose regimens of zileuton 600mg in healthy volunteers.

The pharmacokinetics and pharmacodynamics of zileuton were determined after oral administration of single dose (600mg) and multiple dose regimens [600mg every 8 hours (q8h regimen) and 600mg every 6 hours (q6h regimen)] in 12 healthy male subjects aged 18 to 50 years. Steady-state park plasma concentration (Cmax), time to Cmax, apparent total plasma clearance, and apparent terminal phase volume of distribution values after the q8h and q6h regimens were 3.07 +/- 1.13 and 4.37 +/- 1.02 mg/L, 1.5 +/- 0.9 and 1.5 +/- 0.9 hours, 793 +/- 233 and 579 +/- 162 ml/min (47.6 and 34.7 L/h), and 179 +/- 126 and 115 +/- 29L, respectively (mean +/- SD). Trough zileuton plasma concentrations (Cmin) immediately before the morning dose were higher than Cmin immediately before the afternoon dose, suggesting a diurnal variation in the pharmacokinetics of zileuton. Accumulation of zileuton occurred with more frequent dose administration, although there was no unexpected accumulation of the parent drug or the N-dehydroxyzileuton metabolite. The q6h regimen of zileuton 600mg was superior to the q8h regimen in maintaining trough plasma concentrations of zileuton above 1.5 mg/L, corresponding to approximately 70 to 80% inhibition of leukotriene B4 biosynthesis.

The effect of food on the pharmacokinetics of zileuton.

The present study was undertaken to assess the effect of food on the pharmacokinetic parameters of zileuton. In a nonblinded crossover study, 18 healthy male volunteers who had fasted overnight were randomised to receive a single oral dose of zileuton 600mg in the presence or absence of food consisting of a standardised breakfast on the following morning. The mean zileuton peak plasma concentration (Cmax) increased significantly by 27% after food intake, while the mean area under the plasma concentration versus time curve increased by only 1.4%, a difference that was not statistically significant. The mean time to Cmax was unaffected by the presence of food, as were the other pharmacokinetic parameters assessed. Overall, the results suggest that food has a relatively small effect on the rate of zileuton absorption compared with the fasting state, while the bioavailability of the drug appears to be unaffected. Thus, it is concluded that it is appropriate to administer zileuton with or without food.

Assessment of the pharmacokinetic interaction between zileuton and digoxin in humans.

The effects of coadministration of zileuton on the pharmacokinetic profile of digoxin were investigated in a double-blind placebo-controlled crossover study in 12 healthy male volunteers. During each study phase, the subjects received zileuton 600mg every 6 hours (regimen A) or placebo (regimen B) for 13 days. In addition, all subjects received concomitant digoxin 0.25 mg/day on study days 1 to 11 during both study phases. The study results provide no evidence of any significant overall effect of zileuton on digoxin plasma concentration-time profiles. Although the mean time to reach the maximum plasma concentration for digoxin was significantly shorter after concomitant administration of digoxin and zileuton than after concomitant administration of digoxin and placebo (0.95 vs 1.43 hours), there were no significant differences between the 2 regimens in the values for maximum plasma concentration, area under the plasma concentration-time curve from 0 to 24 hours, elimination half-life, oral clearance, and apparent volume of distribution associated with the terminal phase. Therefore, it is concluded that digoxin and zileuton may be coadministered without risk of clinically relevant effects on the pharmacokinetic profile of digoxin.

The influence of multiple oral doses of zileuton on the steady-state pharmacokinetics of sulfasalazine and its metabolites, sulfapyridine and N-acetylsulfapyridine.

The effects of zileuton (Abbott-64077) on the pharmacokinetics of sulfasalazine (SASP) and its metabolites, sulfapyridine (SP) and N-acetylsulfapyridine (ASP), were studied in a randomised double-blind placebo-controlled study enrolling 14 healthy male volunteers. All subjects received SASP 1 g every 12 hours for 8 days and zileuton 800mg or placebo administered twice daily from day 4 to day 8 inclusive. Coadministration of zileuton did not significantly affect the area under the plasma concentration-time curve, the maximum (Cmax) or minimum (Cmin) plasma concentration and the time to Cmax of SASP, SP or ASP. Likewise, zileuton did not modify the terminal elimination half-life of SASP. It is concluded that coadministration of zileuton 1.6 g/day has no significant effects on the pharmacokinetics of SASP 2 g/day or its metabolites, SP and ASP.

Pharmacokinetic interactions between zileuton and prednisone.

A randomized double-blind placebo-controlled crossover study evaluated the effects of zileuton 600mg 4 time daily on the pharmacokinetics of prednisolone after a single 400mg oral dose of prednisone. the effects of the single prednisone dose on the steady-state pharmacokinetics of zileuton were also evaluated. Multiple doses of zileuton had no significant effects on mean peak plasma concentration (Cmax), time to Cmax(tmax), or area under the plasma concentration-time curve from 0 to infinity (AUC0-infinity) values for prednisolone after oral administration of prednisone 40mg. A slight but statistically significant increase in the mean half-life (t1/2) of prednisolone was detected with zileuton + prednisone administration compared with prednisone + placebo (from 2.8 to 2.9 hours); however, this change was of no clinical relevance. Mean Cmax values of zileuton after coadministration with prednisone were similar to those of zileuton alone. While the single 40mg dose of prednisone resulted in a slight but statistically significant decrease in the mean zileuton AUC value from 0 to 6 hours (AUC0-6) [from 23 to 20 mg/L/h] and a reduction in tMAX (from 2.3 to 1.7 hours), these results were not considered to be clinically significant. Therefore, it is considered that zileuton and prednisone may be coadministered with minimal risk of a clinically significant pharmacokinetic interaction.

The pharmacokinetic and pharmacodynamic interactions between the 5-lipoxygenase inhibitor zileuton and the cyclo-oxygenase inhibitor naproxen in human volunteers.

The potential pharmacokinetic and pharmacodynamic interactions between zileuton, a 5-lipoxygenase inhibitor, and naproxen, a nonsteroidal anti-inflammatory drug that acts as a cyclo-oxygenase inhibitor, have been investigated in 24 healthy volunteers. Coadministration of these 2 drugs had no effect upon the plasma concentration-time curves of either zileuton (800mg) or naproxen (500mg) when compared with each drug administered alone. Both naproxen plasma concentrations during the elimination phase and area under the plasma concentration-time curve values were statistically significantly raised upon coadministration with zileuton, when compared with naproxen alone. However, these differences in these 2 values were sufficiently small to be of no clinical significance. There is no evidence that the combination of zileuton and naproxen had an effect on leukotriene B4 levels that was different from the inhibitory effect of zileuton alone, or had an effect on serum thromboxane B2 levels that was different from the effect of naproxen alone. Moreover, inhibition of the 5-lipoxygenase pathway by zileuton did not appear to aggravate the gastrointestinal adverse events commonly associated with naproxen administration. It is concluded that zileuton and naproxen may be coadministered with minimal risk of a clinically significant interaction.