Clinical, hematologic, and immunologic effects of interleukin-10 in humans

We conducted a double-blind, placebo-controlled study to investigate the safety, pharmacokinetics, and immunological properties of interleukin-10 (IL-10) administration in healthy humans. Volunteers received a single intravenous bolus injection of recombinant human IL-10 (1, 10, or 25 micrograms/kg) or placebo. Cytokine production in whole blood and peripheral blood mononuclear cells (PBMC) was assessed before and 3, 6, 24, and 48 hr after the injection. Peak serum concentrations of IL-10 (15 +/- 1.1, 208 +/- 20.1, and 505 +/- 22.3 ng/ml) occurred after 2-5 min for 1, 10, and 25 micrograms/kg IL-10, respectively. The terminal-phase half-life was 3.18 hr. A transient leukocytosis (24-63% above baseline) was observed 6 hr after injection, which coincided with a dose-dependent decrease (12-24%) in neutrophil superoxide generation. There was a marked inhibition (60-95%) of endotoxin-induced IL-6 production from whole blood in each group receiving IL-10. Production of IL-8 in endotoxin-stimulated blood was reduced in the 10 micrograms/kg group. In PBMC stimulated with phytohemagglutinin and phorbol ester, there was a decrease (72-87%) in interferon-gamma (IFN gamma) production 6 hr after IL-10 with a return to pre-IL-10 levels after 24 hr. This reduction was only partially associated with a decrease in the number of CD2-bearing cells. We conclude that IL-10 administration into humans is without significant side effects, and a single injection reduces ex vivo production of IL-6, IL-8, and IFN gamma.

Effect of felbamate on the pharmacokinetics of lamotrigine

To assess the possible interaction between lamotrigine and felbamate, a double-blind, randomized, placebo-controlled, two-way crossover study was conducted in 21 healthy male volunteers. Volunteers were given lamotrigine (100 mg every 12 hours) and felbamate (1,200 mg every 12 hours) or matching placebo for 10 days during each period of the crossover. After morning administration on day 10, blood samples were obtained over 12 hours for measurement of lamotrigine. Felbamate increased the maximum concentration (Cmax) and and area under the concentration-time curve from time 0 to 12 hours (AUC0-12) of lamotrigine by 13% and 14%, respectively, compared with placebo. The 90% confidence intervals of the log-transformed pharmacokinetic parameters were within the 80-125% bioequivalance limits, however. Felbamate had no significant effect on the urinary excretion of lamotrigine (total), unconjugated lamotrigine, or the N-glucuronide. One volunteer discontinued the study after developing a rash while taking lamotrigine and placebo. All other adverse events were primarily related to the central nervous system and gastrointestinal tract, with a higher incidence reported during coadministration of lamotrigine and felbamate than with placebo. Overall, felbamate appears to have no clinically relevant effects on the pharmacokinetics of lamotrigine.

The effect of age on the apparent clearance of felbamate: a retrospective analysis using nonlinear mixed-effects modeling

The effects of age on felbamate apparent clearance were examined through a retrospective analysis of plasma concentration data from 700 pediatric and adult epileptic patients (age range, 2-74 years) enrolled in six clinical studies. Patients received felbamate as monotherapy or in combination with either the antiepileptic drugs (AEDs) carbamazepine (CBZ), phenytoin (PHT), or valproate (VPA). Data were analyzed using a nonlinear mixed-effects pharmacostatistical modeling technique (NONMEM). Factors in the model included age, body weight, and concomitant AEDs. Apparent clearance was highest in the very young and decreased during the early teenage years, with minimal changes observed beyond 13 years. Mean apparent clearance values were approximately 40% higher in children (2-12 years) compared with those in adults (13-65 years). This pattern and its magnitude were consistent whether felbamate was administered alone or coadministered with CBZ, PHT, or VPA. The increase in clearance is minimal compared with other AEDs including PHT, CBZ, and phenobarbital. Enzyme-inducing AEDs (CBZ and PHT) increased felbamate apparent clearance by 32-38% relative to monotherapy, whereas coadministration with VPA had a minimal effect on felbamate apparent clearance. Dose/concentration linearity was observed at all ages during mono- or polytherapy. These findings suggest that felbamate dosing should be relatively uncomplicated in children relative to that in adults.

Pharmacokinetics and immunomodulatory properties of intravenously administered recombinant human interleukin-10 in healthy volunteers

Normal volunteers received single doses of recombinant human interleukin-10 (rhIL-10; n = 6 per group) or placebo (n = 3 per group) by intravenous injection to characterize pharmacokinetics, tolerability, and immunomodulatory effects. Dosages were 0.1, 0.5, 1.0, 2.5, 5.0, 10.0, 25.0, 50.0, and 100.0 micrograms/kg. Dose-related adverse effects consisted of a mild-to-moderate flu-like syndrome characterized by fever with chills, headache, and myalgias at the highest dose. The mean terminal phase t1/2 ranged from 2.3 +/- 0.5 to 3.7 +/- 0.8 hours. Dose-related effects of rhIL-10 included transient increases of circulating neutrophils and monocytes and decreases of lymphocytes. rhIL-10 markedly suppressed, in a time- and dose-dependent manner, the synthesis of the inflammatory cytokines IL-1 beta and tumor necrosis factor alpha by whole blood stimulated ex vivo with bacterial lipopolysaccharide. Circulating numbers of CD14+/HLA-DR+ cells at 24 hours after the dose were increased in a dose-dependent manner. Effects on expression of HLA-DR by CD14+ cells were variable. There was no apparent effect on HLA-DR expression by CD20+ cells. The immunomodulatory effects of rhIL-10 merit further clinical investigation.

Loratadine administered concomitantly with erythromycin: pharmacokinetic and electrocardiographic evaluations

OBJECTIVE

To evaluate the effects of coadministration of loratadine and erythromycin on the pharmacokinetics and electrocardiographic repolarization (QTc) pharmacodynamics of loratadine and its metabolite descarboethoxyloratadine in healthy volunteers.

METHODS

Twenty-four healthy volunteers were studied in a prospective, double-blind crossover design while confined in a Clinical Research Center. The primary pharmacodynamic end point of the study was the difference between baseline and day 10 mean QTc intervals obtained from surface electrocardiograms. Plasma concentrations of loratadine, descarboethoxyloratadine, and erythromycin were measured on treatment day 10 for pharmacokinetic analysis. Subjects received in random sequence the following three treatments for 10 consecutive days during three separate study periods: 10 mg loratadine every morning plus 500 mg erythromycin stearate every 8 hours, or 10 mg loratadine every morning plus placebo every 8 hours, or placebo every morning plus 500 mg erythromycin stearate.

RESULTS

Concomitant administration of loratadine and erythromycin was associated with increased plasma concentrations of loratadine (40% increase in area under the plasma concentration-time curve [AUC]) and descarboethoxyloratadine (46% increase in AUC) compared with loratadine alone. Analysis of variance showed no difference between the treatment groups in effect on QTc intervals compared with baseline, and no significant change from baseline was observed. No clinically relevant changes in the safety profile of loratadine were observed, and there were no reports of sedation nor syncope.

CONCLUSION

Although concomitant administration of loratadine and erythromycin was associated with increased plasma concentrations of loratadine and descarboethoxyloratadine, no clinically relevant changes in the safety profile of loratadine were observed. In this study, 10 mg loratadine administered orally for 10 consecutive days was well tolerated when coadministered with therapeutic doses of erythromycin stearate.

Biopharmaceutic characteristics of a new extended-release theophylline formulation (Uni-Dur)

BACKGROUND

There is a close relationship between improvement in airway function and the plasma concentration of theophylline, as well as between rapidly rising plasma theophylline concentrations and increased frequency of undesired effects. Development of pharmaceutical formulations and prescribed dosage intervals for theophylline dosage forms should therefore be directed toward providing the most stable plasma concentrations attainable.

OBJECTIVE

To characterize the steady-state biopharmaceutic profile of Uni-Dur following once-daily or twice-daily administration.

METHODS

Twenty-four adult male volunteers with average theophylline clearance (3.0 and 5.5 L.h-1) received three treatments on separate occasions: Uni-Dur 800 mg once-daily, Uni-Dur 400 mg twice-daily, and Uniphyl 800 mg once-daily. Treatments were taken after a meal for five days with at least 1 week washout between treatment periods. Trough blood samples were collected prior to the AM dose on days 3, 4, and 5, and at specified intervals up to 48 hours after the AM dose on day 5 for subsequent determination of theophylline concentrations in plasma.

RESULTS

The area under the plasma concentration-time curve (AUC; microgram.mL-1.h) for theophylline over 24 hours on day 5 was 187 for Uni-Dur 800 mg once-daily, 187 for Uni-Dur 400 mg twice-daily, and 172 for Uniphyl 800 mg once-daily; the peak plasma concentrations were 10.4, 9.4, and 11.0 micrograms.mL-1 and the trough concentrations were 5.5, 7.2, and 3.5 micrograms.mL-1, respectively; fluctuation index (peak minus trough divided by trough) was 78%, 16%, and 231%, respectively. No further accumulation of theophylline occurred after day 3. No serious nor severe adverse events were reported during any treatment.

CONCLUSIONS

Uni-Dur is an extended-release formulation that provides stable plasma concentrations of theophylline over a 24-hour period with less fluctuation than observed with a once-daily reference formulation. In subjects with normal theophylline clearance, Uni-Dur administered twice-daily provided remarkably stable theophylline plasma concentrations over a 24-hour period. Absorption of theophylline from Uni-Dur was not affected by food, and no evidence of dose-dumping was observed. Uni-Dur should provide efficacious theophylline therapy with minimal adverse events in patients with symptoms of asthma and reversible bronchospasm associated with chronic bronchitis and emphysema.

Lack of hypothalamic-pituitary-adrenal axis suppression with once-daily or twice-daily beclomethasone dipropionate aqueous nasal spray administered to patients with allergic rhinitis

The potential for a newly developed, double-strength (0.084%) beclomethasone dipropionate (BDP) aqueous (AQ) nasal suspension to produce effects associated with exposure to systemic corticosteroids was assessed by the plasma cortisol response to cosyntropin stimulation induced by a 6-hour intravenous infusion of 250 micrograms of cosyntropin in 500 mL of normal saline. Sixty-four patients with allergic rhinitis were enrolled in this study. Patients were randomly assigned to one of the following four treatment groups: (1) BDP AQ Forte (0.084%) nasal spray 336 micrograms once daily; (2) BDP AQ (0.042%) nasal spray 168 micrograms twice daily; (3) placebo nasal spray twice daily; or (4) oral prednisone 10 mg once daily in the morning. After 36 consecutive days of treatment, there was a significant (P < 0.01) difference in the plasma cortisol response to cosyntropin stimulation between the prednisone and placebo groups; however, there were no significant differences between the BDP AQ Forte or the BDP AQ groups compared with the placebo group. Secondary analyses comparing BDP AQ Forte administered as 336 micrograms once daily with BDP AQ administered as 168 micrograms twice daily showed no significant differences in plasma cortisol responses to cosyntropin stimulation. No serious adverse events were reported. Adverse events consisted of headache, pharyngitis, or nasal irritation, with headache being reported most frequently. These adverse events were similarly distributed among active treatment groups and were similar to placebo. No clinically relevant changes were observed in any treatment group in findings on clinical laboratory tests, physical examination, or electrocardiography. Vital signs, obtained daily, were consistent with values observed in healthy individuals. No patient exhibited signs of oral candidiasis. All patients met the plasma cortisol concentration criteria for discharge relative to expected hypothalamic-pituitary-adrenal axis function. In conclusion, there were no significant differences in plasma cortisol responses to cosyntropin stimulation between groups of patients with allergic rhinitis treated with either BDP AQ Forte (0.084%) nasal spray 336 micrograms once daily or BDP AQ (0.042%) nasal spray 168 micrograms twice daily compared with the placebo group. These results indicate that the dosing regimens of BDP AQ nasal suspensions used in this study lack systemic effects and are safe and well tolerated.

Pharmacokinetics of isepamicin

Isepamicin is a new aminoglycoside that has activity against many bacteria resistant to other aminoglycosides. The pharmacokinetics of isepamicin have been characterized in neonatal, pediatric, adult, elderly and renally impaired human populations as well as in clinical trials using the techniques of population pharmacokinetics. The pharmacokinetics of isepamicin are uncomplicated and generally similar to those of other aminoglycosides, although there is some evidence that it may have less tissue accumulation. The drug is completely absorbed following intramuscular administration. The drug is not metabolized and unchanged isepamicin accounts for all of the drug substance in plasma and urine. It is completely eliminated via the renal route; consequently dosing in patients with renal insufficiency has to be adjusted according to the degree of renal impairment. The pharmacokinetics of isepamicin are generally linear. Thus peak plasma concentrations and area under the plasma concentration curve (AUC) values are proportional to the administered dose while clearance (1.1-1.3 mL/min/kg), volume of distribution at steady state (0.23-0.29 L/kg) and half-life (2-2.5 h) are independent of dose. There is no significant accumulation of drug in the plasma with once- or twice-daily dosing. The isepamicin plasma concentration curve following a 1 g intravenous dose to healthy volunteers can be best characterized by a tri-exponential curve corresponding to a t1/2 alpha of 0.17 h, a t1/2 beta of 2.1 h, and a gamma-phase of 34 h. The t1/2 beta represents the elimination phase and changes with age and renal functions, while the gamma-phase represents the return of drug to plasma from a deep compartment including binding in renal tissue. The gamma-phase represents less than 3% of the total AUC and does not change with age. Isepamicin readily distributes to extracellular fluid and pulmonary tissue. In conclusion, isepamicin demonstrates predictable linear kinetics and is similar pharmacokinetically to other aminoglycosides. Preliminary indications of decreased tissue accumulation implied from pharmacokinetic and pharmacodynamic characteristics of isepamicin favour once-daily dosing.

Pharmacokinetics of isosorbide-5-mononitrate after oral administration of an extended-release mononitrate formulation versus a standard dinitrate formulation

The steady-state pharmacokinetic profile of isosorbide-5-mononitrate (5-ISMN) after oral administration of an extended-release tablet formulation of 5-ISMN 60 mg or 120 mg once a day was compared with that after administration of isosorbide dinitrate (ISDN) 40 mg every 6 hours, in a randomized, open-label, three-way crossover trial in 24 healthy men. After oral administration of extended-release 5-ISMN 60 mg or 120 mg once daily, 5-ISMN was slowly absorbed, reaching mean peak plasma concentrations of 557 and 1151 ng/mL, respectively, in approximately 3 hours. Plasma concentrations of 5-ISMN were dose proportional between 60 mg and 120 mg. After oral administration of ISDN 40 mg every 6 hours, a mean peak plasma 5-ISMN concentration of 806 ng/mL was achieved in less than 2 hours (mean time to reach the maximum plasma concentration was 1.5 hours). The mean plasma apparent elimination half-life of 5-ISMN was 6.2 hours after extended-release 5-ISMN administration and 7.1 hours after ISDN. Although the maximum plasma concentration was higher and the minimum plasma concentration was lower after administration of extended-release 5-ISMN 120 mg once daily compared with ISDN 40 mg every 6 hours, there was no significant difference (P > 0.05) in the "bioavailability" of 5-ISMN between these two treatments. The most commonly reported adverse events in these "nitrate-naive" subjects were headache, dizziness, nausea, and vomiting; these were dose related and their incidence decreased with repeated exposure.

Effect of food on the oral bioavailability of isosorbide-5-mononitrate administered as an extended-release tablet

We evaluated the effect of a high-fat breakfast and gastric emptying rate on the oral bioavailability of a isosoribide-5-mononitrate (5-ISMN) controlled-release tablet formulation (IMDUR 60-mg tablets, Astra Hässle AB, Mölndal, Sweden) relative to an oral solution in 18 healthy men. Gastric emptying was monitored by radiotelemetry using the Heidelberg capsule technique. After administration of the 5-ISMN 60-mg solution, absorption was rapid with mean peak plasma 5-ISMN concentrations of 1533 ng/mL achieved in less than 1 hour. In contrast, after administration of IMDUR 60-mg tablets, the drug was more slowly absorbed, reaching mean peak plasma concentrations of 541 ng/mL in 3 to 4 hours. The bioavailability of 5-ISMN from IMDUR tablets under fasted conditions was approximately 78% relative to the solution; and, in the presence of food, the bioavailability was slightly increased to 86% (P = .057). The mean gastric residence time of IMDUR tablets under fasted conditions was 68 minutes, and in the presence of food was increased to 478 minutes, with 9 of the 18 subjects having gastric emptying delayed for at least 600 minutes. We conclude that in the presence of food, gastric emptying time is considerably increased causing a delay in drug absorption and a slight increase in the bioavailability of 5-ISMN from this controlled-release tablet formulation, however this effect is not clinically relevant.

Pharmacokinetics of the triazole antifungal agent genaconazole in healthy men after oral and intravenous administration

The pharmacokinetics of genaconazole, a potent new difluorophenyl-triazole antifungal agent, was studied in 12 healthy male volunteers following a single oral or intravenous administration of the drug. In a randomized two-way crossover design, each volunteer received either two 50-mg genaconazole tablets orally or a parenteral preparation containing 100 mg of genaconazole given as a 30-min intravenous infusion. Both dosage regimens were well tolerated. Blood and urine samples were collected up to 10 days after drug administration. Concentrations of genaconazole in plasma and urine were determined by a specific high-performance liquid chromatography assay with a limit of quantitation of 0.1 microgram/ml. Pharmacokinetic evaluation following oral and intravenous doses indicated that mean values for the area under the concentration-time curve from 0 h to infinity (137 and 136 micrograms.h/ml), half-life (50 and 49 h), volume of distribution (52 and 52 liters), and clearance (12 and 12 ml/min) were independent of the route of drug administration. The oral and intravenous administrations of genaconazole yielded virtually superimposable plasma concentration-time curves, resulting in an absolute bioavailability of 100%. Amounts of unchanged genaconazole found in urine samples from 0 to 240 h after oral and intravenous doses were comparable, and urinary excretion accounted for 76 and 78% of the administered dose, respectively. Renal clearances for the two routes of administration were also similar, and renal clearance accounted for over 80% of the total body clearance. The 100% absolute bioavailability of genaconazole regardless of the route of administration provides greater dosing flexibility in various clinical settings than currently exists.

Effects of caffeine or ethanol on treadmill performance and metabolic responses of well-trained men

The effects of caffeine and ethanol on treadmill performance and metabolic responses to exercise were determined in four trained runners. Caffeine (2.5 mg.kg-1 body weight) or ethanol (25 ml) in 150 ml of grapefruit juice (total volume) or grapefruit juice (placebo) was randomly administered 10 minutes prior to and at 30 minutes of a 60 minutes treadmill run. The speed and grade of the treadmill was adjusted to elicit an average oxygen consumption of 80-85% of the subject's maximal oxygen consumption. All subjects completed the treadmill run for the caffeine and placebo conditions. Three of the four subjects could not complete the treadmill run following the second administration of ethanol. Exercise heart rate was significantly greater for the ethanol condition than for the placebo condition. Exercise oxygen consumption was greater following ethanol administration than for placebo, but the differences were not significant. Blood glucose rose significantly between 0 and 30 minutes of treadmill running for all three conditions. Between 30 minutes of treadmill running and either 60 minutes or the time of termination of the exercise, blood glucose decreased significantly by 24% following the second ethanol treatment. Plasma fatty acid, triglyceride, creatine phosphokinase, and renin contents followed expected exercise changes with a blunting of the rise of plasma fatty acids at 30 minutes of exercise for the ethanol condition. It was concluded that the administration of ethanol adversely influenced treadmill exercise performance by eliciting a hypoglycemic effect between 30 minutes and the termination of the exercise.

Effect of ethanol on metabolic responses to treadmill running in well-trained men

The metabolic effects of ethanol on treadmill performance were determined in four trained runners. Ethanol in doses of 25 mL in 150 mL of grapefruit juice (total volume) or grapefruit juice was randomly administered 10 minutes before and at 30 minutes of a 60-minute treadmill run. The speed and grade of the treadmill was adjusted to elicit an average oxygen consumption (VO2) of 80 to 85% of the subjects' VO2max. Three of the four subjects could not complete the treadmill run after the administration of ethanol. Administration of ethanol resulted in significant increases in the heart rate responses to treadmill running above those for the placebo grapefruit treatment. VO2 was higher after ethanol administration than the placebo grapefruit juice treatment, but these values were not significant. Blood glucose content rose significantly between 0 and 30 minutes of treadmill running for both the ethanol and placebo grapefruit juice treatments. Between 30 minutes of treadmill running and the termination of the exercise, the blood glucose level decreased significantly by 24% after the second ethanol treatment at 30 minutes of exercise. Plasma fatty acid, triglyceride, creatine phosphokinase, and renin contents followed expected exercise changes. It was concluded that the administration of ethanol adversely influenced treadmill exercise performance by eliciting a hypoglycemic effect between 30 minutes and the termination of the exercise.

Effect of concomitant administration of piperacillin on the dispositions of isepamicin and gentamicin in patients with end-stage renal disease

Piperacillin inactivation of the aminoglycosides isepamicin and gentamicin in 12 chronic hemodialysis patients was assessed. Six subjects each received isepamicin (7.5 mg/kg of body weight) or gentamicin (2 mg/kg) alone and in combination with piperacillin (4 g every 12 h for four doses). Isepamicin and gentamicin concentrations in plasma and urine were monitored over 48 h after each dose and analyzed by high-performance liquid chromatography and fluorescence polarization immunoassay, respectively. The pharmacokinetics of isepamicin were not significantly altered during combination treatment with piperacillin. The total body clearance (3.79 +/- 0.71 versus 3.94 +/- 1.05 ml/min), the steady-state volume of distribution (0.19 +/- 0.04 versus 0.18 +/- 0.03 liter/kg), and the terminal elimination half-life (47.91 +/- 7.20 versus 45.08 +/- 10.34 h) were not significantly altered in the presence of piperacillin. In contrast, the terminal elimination half-life (47.68 +/- 20.58 versus 35.67 +/- 11.18 h) of gentamicin was significantly reduced when gentamicin was given with piperacillin. The total body clearance (4.26 +/- 3.07 versus 4.89 +/- 1.94 ml/min) and the steady-state volume of distribution (0.19 +/- 0.04 versus 0.20 +/- 0.04 liter/kg) of gentamicin were not significantly altered during combination therapy; however, the nonrenal clearance of gentamicin administered in combination with piperacillin (3.56 +/- 0.38 ml/min) increased significantly compared with that of gentamicin (2.03 +/- 0.50 ml/min) given alone. The results of this study suggest that no additional dosage adjustment of isepamicin during concomitant therapy with piperacillin in hemodialysis patients is necessary. However, this does not preclude the need for appropriately ex vivo-handled specimens for monitoring isepamicin concentrations in plasma to ensure therapeutic efficacy and prevent toxicity. Furthermore, additional dosage adjustments may be necessary when gentamicin is used concomitantly with piperacillin, on the basis of the significant in vivo inactivation that takes place in end-stage renal disease patients.

Differential plasma duration of antiplatelet-activating factor and antihistamine activities of oral Sch 37370 in humans

Preclinical studies have established that Sch 37370 (1-acetyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]-cyclohepta [1,2-b]pyridin-11-ylidene)piperidine) is an orally active antagonist of platelet-activating factor (PAF) and histamine H1-receptors with potential therapeutic use in the treatment of asthma. To evaluate the efficacy and duration of anti-PAF and antihistamine actions of oral Sch 37370 in humans, a single dose (5 mg/kg) of Sch 37370 was given orally to each of 10 male subjects in a placebo-controlled, double-blind crossover study. Blood samples were drawn before and at various times (2 to 48 hours) after Sch 37370 or placebo. Plasma samples were analyzed for Sch 37370 by a gas chromatographic method, for the anti-PAF activity by measuring the aggregation of platelets stimulated with PAF, and for the antihistamine activity by measuring displacement of [3H]pyrilamine from rat brain membrane binding sites. The plasma anti-PAF activity declined from high levels at 2 hours to barely detectable levels at 24 hours; however, significant activity was still present at 12 hours. The plasma levels of Sch 37370 closely paralleled the anti-PAF profile. The plasma antihistamine activity reached a maximum within 2 to 8 hours and declined thereafter. However, 48 hours after Sch 37370, the antihistamine activity was still present at a significant level in most subjects. It is concluded that, in humans, oral Sch 37370 antagonizes both PAF and histamine with plasma antihistamine activity lasting longer than plasma anti-PAF activity.

Isepamicin disposition in subjects with various degrees of renal function

The disposition of isepamicin, an investigational aminoglycoside antibiotic, was evaluated in 30 subjects with various degrees of renal function. The subjects were divided into five groups: those with normal renal function (creatinine clearance [CLCR], greater than 80 ml/min/1.73 m2), those with mild renal insufficiency (CLCR, 50 to 80 ml/min/1.73 m2), those with moderate renal insufficiency (CLCR, 30 to 49 ml/min/1.73 m2), those with severe renal insufficiency (CLCR, 5 to 29 ml/min/1.73 m2), and those maintained on hemodialysis (CLCR, less than 5 ml/min/1.73 m2). Subjects on hemodialysis were studied both during hemodialysis and during an interdialytic period. The volumes of distribution of isepamicin were not significantly different among the five groups of patients. The total body clearance (CLP) and renal clearance (CLR) of isepamicin significantly decreased as CLCR decreased. The CLP of isepamicin and CLCR were significantly related [(COP = 0.391.[CLCR] + 1.83; r2 = 0.878)]. Nonrenal clearance of isepamicin did not differ between groups. Hemodialysis augmented the CLP of isepamicin by approximately 25-fold. The amount of isepamicin recovered in the dialysate was 60.6 +/- 15.8% of the dose administered. The maximal rebound of the isepamicin concentration in plasma after cessation of hemodialysis was observed at 0.78 +/- 0.7 h. Concentrations in plasma increased 32.7 +/- 22.9% over that measured at the end of hemodialysis. These data indicate that dosage adjustments are necessary in subjects with decreased renal function.

Pharmacokinetics of ceftibuten-cis and its trans metabolite in healthy volunteers and in patients with chronic renal insufficiency

The impact of renal insufficiency on the dispositions of 300 mg of orally administered ceftibuten-cis, a new broad-spectrum oral cephalosporin, and its primary metabolite ceftibuten-trans was characterized in 30 adult subjects. Subjects were divided into five groups of six subjects each on the basis of their 24-h ambulatory creatinine clearances (CLCR). The apparent total body clearance (CLP/F; where F is absolute bioavailability) and renal clearance of ceftibuten-cis were significantly lower in subjects with end-stage renal disease (on maintenance hemodialysis; group V) and in those with severe (CLCR, 5 to 29 ml/min; group IV) and moderate (CLCR, 30 to 49 ml/min; group III) renal insufficiency than in those with mild renal insufficiency (CLCR, 50 to 80 ml/min; group II) or normal renal function (CLCR, greater than 80 ml/min; group I). A significant correlation was observed between CLCR and ceftibuten-cis CLP/F. The mean apparent steady-state volume of distribution (V beta/F) of ceftibuten-cis ranged from 0.21 to 0.24 liter/kg in subjects in group I, II, III, and IV. V beta/F was significantly greater in the group V subjects with end-stage renal disease (V beta/F, 0.39 +/- 0.27 liters/kg). These changes in V beta/F cannot be separated from possible changes in bioavailability. The maximum concentration of ceftibuten-trans in plasma was significantly higher and occurred significantly later in group IV subjects than it did in subjects in the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Stepwise determination of multicompartment disposition and absorption parameters from extravascular concentration-time data. Application to mesoridazine, flurbiprofen, flunarizine, labetalol, and diazepam

When disposition is monoexponential, extravascular concentration-time (C, t) data yield both disposition and absorption parameters, the latter via the Wagner-Nelson method or deconvolution which are equivalent. Classically, when disposition is multiexponential, disposition parameters are obtained from intravenous administration and absorption data are obtained from extravascular C, t data via the Loo-Riegelman or Exact Loo-Riegelman methods or via deconvolution. Thus, in multiexponential disposition one assumes no intrasubject variation in disposition, a hypothesis that has not been proven for most drugs. Based on the classical two- and three-compartment open models with central compartment elimination, and using postabsorptive extravascular C, t data only, we have developed four equations to estimate k10 when disposition is biexponential and two other equations to estimate k10 when disposition is triexponential. The other disposition rate constants are readily obtained without intravenous data. We have analyzed extravascular data of flurbiprofen (12 sets), mesoridazine (20 sets), flunarizine (5 sets), labetalol (9 sets), and diazepam (4 sets). In the case of diazepam intravenous C, t data were also available for analysis. After disposition parameters had been estimated from the extravascular data the Exact Loo-Riegelman method with the Proost modification was applied to the absorptive extravascular data to obtain AT/VP as a function of time. These latter data for each subject and each drug studied were found to be fitted by a function indicating either simple first-order absorption, two consecutive first-order processes, or zero-order absorption. After absorption and disposition parameters had been estimated, for each set of extravascular data analyzed, a reconstruction trend line through the original C, t data was made. The new methods allow testing of the hypothesis of constancy of disposition with any given drug. There is also a need for new methods of analysis since the majority of drugs have no marketed intravenous formulation, hence the classical methods cannot be applied.

The effect of antacid and cimetidine on the oral absorption of the antifungal agent SCH 39304

The single-dose pharmacokinetics of the antifungal agent SCH 39304 (Schering-Plough Corp., Kenilworth, NJ) were assessed alone and in combination with antacid and cimetidine. On three separate occasions nine healthy men received a single oral 50 mg dose of SCH 39304 either alone, with 60 mL antacid, or with oral cimetidine 300 mg four times a day for 4 days. Concomitant antacid or cimetidine administration had no significant effect on any of the SCH 39304 pharmacokinetic parameters studied. The oral absorption of SCH 39304, as assessed by the area under the plasma concentration-time curve (AUC) and the amount of drug recovered unchanged in the urine, was not affected by either antacid or cimetidine. The AUC0-1 for the drug given alone was 80.5 +/- 15.8 micrograms.hr/mL, compared to 81.4 +/- 12.7 and 79.7 +/- 9.6 micrograms.hr/mL with concomitant antacid and cimetidine, respectively. The amount of drug excreted in the urine (Ae0-1) was 22.7 +/- 5.1, 24.2 +/- 9.2, and 23.6 +/- 7.6 mg when the drug was given alone, with antacid, and with cimetidine, respectively. Antacid coadministration delayed absorption as evidenced by an increase in the tmax in 7 out of 9 subjects, although this did not reach statistical significance (P = .082, Wilcoxon test). We conclude that concomitant antacid or cimetidine does not alter the oral absorption or pharmacokinetic disposition of single-dose SCH 39304.

Pharmacokinetics and pharmacodynamics of dilevalol

The pharmacokinetics and pharmacodynamics of dilevalol, the R,R stereoisomer of labetalol, were evaluated in nine subjects. Dilevalol was given as a single 50 mg intravenous dose and as a 400 mg daily oral dose for 7 days. To study the effects of hepatic enzyme inhibition, each subject received dilevalol in the presence of and absence of cimetidine. Cardiac beta-blockade was assessed by use of standardized treadmill tests for 48 hours after oral dilevalol. The three-compartment model analysis showed that systemic clearance (29.8 +/- 5.7 ml/min/kg), volume of distribution (16.6 +/- 4.1 L/kg), and terminal half-life (11.7 +/- 2.7 hours) were not altered by cimetidine. However, there was a 20% increase in the area under the curve (p less than 0.05) and an 11% increase in systemic bioavailability (p less than 0.05) after oral administration. Dilevalol caused significant cardiac beta-blockade for more than 24 hours, but these effects were not altered by cimetidine. The pharmacokinetic changes are consistent with a decrease in first-pass extraction of a high clearance drug.

Vasodilation and reduction in forearm vascular resistance after acute administration of dilevalol

Dilevalol is a long-acting antihypertensive drug that has been demonstrated in animals to combine specific beta 2-agonist-mediated vasodilation with nonspecific beta blockade. To document vasodilation in humans, single oral doses of dilevalol, 200 mg, and placebo were randomly administered to 12 untreated hypertensive patients. Dilevalol produced significant reductions (p less than or equal to 0.01) in diastolic blood pressure throughout a 24-hour period relative to placebo, without changing heart rate. Forearm blood flow, measured hourly over the initial 4 hours after dosing, demonstrated a shift to a more vasodilated state after dilevalol administration, with significant increases in minimal forearm blood flow (4.0 vs 2.9 ml/dl tissue/min, dilevalol vs placebo, respectively; p = 0.05) and in mean average forearm blood flow (5.3 vs 4.0 ml/dl tissue/min, dilevalol vs placebo; p = 0.04). Similarly, dilevalol produced a decrease in mean forearm vascular resistance (26.5 vs 34.6 mm Hg/ml/dl tissue/min, dilevalol vs placebo; p = 0.02). In the absence of a change in heart rate, the acute hypotensive response to dilevalol in these patients appears to have resulted primarily from vasodilation and reduced vascular resistance.

Pharmacokinetics of dilevalol in normotensive and hypertensive volunteers

Dilevalol is a novel antihypertensive agent combining vasodilation due to selective beta 2-adrenergic receptor agonism with nonspecific antagonism of beta 1- and beta 2-adrenergic receptors. Studies of dilevalol's pharmacokinetics in normotensive and hypertensive volunteers have demonstrated that (1) it is rapidly and well absorbed; (2) because of extensive first-pass metabolism its absolute oral bioavailability is about 12%; (3) its mean elimination half-life is 8 to 12 hours after administration of single oral or intravenous doses to normal volunteers, a value consistent with once-daily dosing; and (4) food does not appear to alter its bioavailability or pharmacokinetics.

Antihypertensive effect of dilevalol is directly related to dose and plasma concentrations

Dilevalol is a novel antihypertensive agent combining vasodilation due to selective beta 2-adrenergic receptor agonism with nonspecific beta antagonism. To determine the relation of dilevalol dose and plasma concentration to antihypertensive effect, dilevalol (n = 15) or placebo (n = 3) was administered to 18 hypertensive subjects. The study was performed under blinded conditions during a 21-day hospitalization after a 3-week drug-free outpatient phase. In the 15 hypertensive patients receiving dilevalol orally in single morning doses of 200, 400 and 800 mg each for 5 days, the drug was shown to reduce blood pressure effectively for 24 hours at all doses. The antihypertensive effect was significantly related to dose administered and to the concentration of unchanged dilevalol measured in plasma. Dilevalol did not cause excessive changes in heart rate at rest and did not produce postural hypotension. The antihypertensive effectiveness of dilevalol was essentially the same after the first and fifth (steady state) doses at each dose level. Finally, no tendency toward rebound hypertension or tachycardia was observed after the abrupt discontinuation of dilevalol in these patients.

Influence of food on the absorption of albuterol Repetabs

A study was conducted in 12 healthy, nonsmoking male volunteers to examine the effect of food intake on the absorption profile of albuterol repeat-action tablets. This randomized crossover study consisted of two phases separated by a 1-week washout period. All subjects fasted 10 hours preceding drug administration. Each subject received two 4 mg albuterol repeat-action tablets with and without a high fat content breakfast. Plasma albuterol concentrations were determined by a gas chromatographic/mass spectrophotometric assay. Relative bioavailability was assessed by comparing areas under the plasma-albuterol concentration time curves as well as peak concentrations and time to peak concentration. No significant differences were noted between the two treatment phases in the area under the curve or peak plasma concentrations. The areas under the curve were 100 and 105 hr.ng/ml when the drug was administered with and without food, respectively. The corresponding peak plasma concentration values were 9.4 and 10.4 ng/ml, respectively. The only significant difference observed was in the maximum time to reach peak plasma concentrations, which was delayed by about 1 hour when the drug was administered with food. Therefore, food has minimal effect on the absorption of albuterol from repeat-action tablets.