Pharmacokinetics of pilocarpine in subjects with varying degrees of renal function

Data from three separate single-center studies were combined to assess the pharmacokinetics of orally administered pilocarpine. Pilocarpine concentration-time data were used to generate a data set including 42 subjects (34 males, 8 females) with varying degrees of renal function (average of two estimated creatinine clearance rates of 10 to 112 mL/min). Age ranged from 19 to 88 years. Subjects received single oral doses (range: 2.5-20 mg) of pilocarpine. Plasma samples were collected at time 0; at 20 and 40 minutes; and at 1, 1.5, 2, 3, 4, 6, 8, 12, 16, and 24 hours following dose administration. Cmax and AUC were normalized to a 5 mg exposure in those subjects who received doses other than 5 mg. Plasma pilocarpine concentrations were determined by gas chromatography/mass spectrometry. The pharmacokinetic parameters (elimination rate constant, Cmax, tmax, AUC, Vd/F, and Cl/F) in subjects with impaired renal function were similar to results found in other pharmacokinetic studies involving normal healthy volunteers with only Cmax being significantly higher (p < 0.05). No significant regression relationships were noted between creatinine clearance and pilocarpine elimination rate constant, tmax, Vd/F, Cl/F, or AUC. Pilocarpine clearance does not appear to be impaired in patients with varying degrees of renal insufficiency.

Effect of cyclooxygenase-2 inhibition on renal function in elderly persons receiving a low-salt diet. A randomized, controlled trial

BACKGROUND

Most nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both cyclooxygenase-1 (COX-1), whose inhibition is associated with gastrointestinal ulceration, and COX-2, whose inhibition is associated with therapeutic benefits. Although agents that do not produce COX-1 activity may have fewer adverse effects, targeted disruption of the COX-2 allele in mice has resulted in severe renal problems, suggesting that COX-2 inhibition may also produce adverse effects.

OBJECTIVE

To determine the effect of rofecoxib, a member of the coxib class of drugs and a specific inhibitor of the COX-2 enzyme, on renal function in elderly patients.

DESIGN

A randomized, three-period, single-dose crossover study and a randomized, parallel-group, multiple-dose study.

SETTING

Clinical research units.

PATIENTS

75 patients 60 to 80 years of age.

INTERVENTION

In the first study, single doses of rofecoxib, 250 mg (about 5-fold to 20-fold the recommended dose); indomethacin, 75 mg; and placebo were administered to 15 patients. In the second study, multiple doses of rofecoxib, 12.5 or 25 mg/d; indomethacin, 50 mg three times daily; or placebo were administered to 60 patients. Patients in both studies received a low-sodium diet

MEASUREMENTS

Glomerular filtration rate, creatinine clearance, and urinary and serum sodium and potassium values.

RESULTS

Compared with placebo, single doses of rofecoxib and indomethacin decreased the glomerular filtration rate by 0.23 m/s (P < 0.001) and 0.18 mL/s (P = 0.003), respectively. In contrast, respective decreases of 0.14, 0.13, and 0.10 mL/s were observed after multiple doses of rofecoxib, 12.5 mg/d (P = 0.019); rofecoxib, 25 mg (P = 0.029), and indomethacin (P = 0.086) were administered. Changes in creatinine clearance and serum and urinary sodium and potassium were less pronounced.

CONCLUSIONS

The effects of COX-2 inhibition on renal function are similar to those observed with nonselective NSAIDs. Thus, COX-2 seems to play an important role in human renal function.

Comparison of anticoagulant effects and safety of argatroban and heparin in healthy subjects

STUDY OBJECTIVE

To evaluate and compare the relationship between dosage and coagulation parameters, as well as safety profiles, of ascending bolus and infusion dosages of argatroban versus heparin in three phase I studies.

DESIGN

Two randomized, double-blind studies compared argatroban and heparin, and one open-label, dose-escalation study further evaluated argatroban.

SETTING

University teaching hospital clinical research unit.

PATIENTS

Healthy men (aged 22-62 yrs).

INTERVENTION

In the first study, 36 subjects received an argatroban 30-, 60-, 120-, or 240-microg/kg bolus, or a heparin 30-, 60-, 120-, or 240-U/kg bolus for three subjects, then amended to 15, 30, 60, or 120 U/kg. In the second study, 37 subjects received argatroban 1.25, 2.5, 5, or 10 microg/kg/minute with or without a 250-microg/kg bolus, or heparin 0.15, 0.20, 0.25, or 0.30 U/kg/minute with or without a 125-U/kg bolus. In the third study (open-label), nine subjects received an argatroban 250-microg/kg bolus plus an infusion of 15, 20, 30, and 40 microg/kg/minute.

MEASUREMENTS AND MAIN RESULTS

When administered as a bolus dose in the first study, argatroban and heparin both produced dose-related increases in activated clotting time (ACT) and activated partial thromboplastin time (aPTT) within 10 minutes of administration. Dissipation of anticoagulant effect was approximately 4-fold faster for argatroban than for heparin. When administered by infusion with or without a bolus in the second study, argatroban, but not heparin, produced predictable dose-related increases in ACT and aPTT that were generally consistent across both effect measures and modes of administration. Effect steady state was attained by five or more subjects per dosing group receiving argatroban (5-9) but typically two or fewer subjects per group receiving heparin (0-7). Furthermore, upon cessation of infusion, anticoagulant effects dissipated faster for argatroban (effect half-life 18-41 min) than for heparin (effect half-life 23-134 min). When argatroban was infused without a bolus, peak and effect steady-state values for ACT and aPTT generally were attained within 1-3 hours. Data from the second and third studies show that for argatroban dosages up to 40 microg/kg/minute, plasma drug concentrations attained at 4 hours of infusion increased linearly with dose, and weight-adjusted plasma clearance was dose independent. In all studies, argatroban and heparin were well tolerated.

CONCLUSION

Anticoagulation was more predictable with argatroban than with heparin as measured by ACT and aPTT, with comparable safety profiles.

Disposition of recombinant human interleukin-10 in subjects with various degrees of renal function

The pharmacokinetics of intravenously administered recombinant human interleukin-10 (rHuIL-10) were evaluated in 18 subjects with creatinine clearances (Clcr) between 2.7 and 116.7 mL/min/1.73 m2. Serum samples for rHuIL-10 were obtained over a 48-hour period after a single 25 micrograms/kg i.v. bolus infusion. AUC, total body clearance (Clp), and steady-state volume of distribution (Vdss) were derived by compartmental methods. Analysis of serum concentrations showed statistically significant group differences for log-transformed AUC and original scale Clp (p < 0.01). The AUC and effective half-life increased, while the mean Clp of rHuIL-10 decreased as renal function declined. A linear relationship between AUC and Clcr as well as Clp and Clcr demonstrates that the disposition of rHuIL-10 is altered in subjects with renal insufficiency. No serious adverse events were noted.

The effects of fenoldopam, a selective dopamine receptor agonist, on systemic and renal hemodynamics in normotensive subjects

OBJECTIVE

Acute renal failure, frequently a consequence of renal vasoconstriction and subsequent renal ischemia, is a common problem for which no proven preventive or therapeutic agents exist. Fenoldopam is a new, selective, dopamine-1 receptor agonist that causes both systemic and renal arteriolar vasodilation. In hypertensive patients, fenoldopam rapidly decreases blood pressure, increases renal blood flow, and maintains or improves the glomerular filtration rate. We sought to determine a dose of fenoldopam that increases renal blood flow without inducing hypotension in normotensive patients and to explore the role of volume status (sodium replete vs. deplete) in these effects.

DESIGN

Randomized, double-blind, placebo-controlled, cross-over study.

SETTING

Clinical research unit.

PATIENTS

Fourteen normal male volunteers.

INTERVENTIONS

Renal plasma flow (para-aminohippurate clearance) and glomerular filtration rate (inulin clearance) were measured during three fixed, escalating doses of fenoldopam (0.03, 0.1, and 0.3 Lg/kg/min) on both a high-sodium and a low-sodium diet.

MEASUREMENTS AND MAIN RESULTS

Fenoldopam significantly increased renal plasma flow in a dose-dependent manner compared with placebo: 670 + 148 vs. 576 + 85 mUmin at 0.03 iLg/kg/min; 777 + 172 vs. 579 + 80 mUmin at 0.1 tig/kg/min; and 784 + 170 vs. 592 + 165 mUmin at 0.3 ilg/kg/min (p < .05 fenoldopam vs. placebo at all three doses). Glomerular filtration rate was maintained. At the lowest dose (i.e., 0.03 ILg/kg/min), significant renal blood flow increases occurred without changes in systemic blood pressure or heart rate. At 0.1 and 0.3 Lgl/kg/ min, systolic blood pressure did not change, but diastolic blood pressure was slightly lower in the fenoldopam group than in the placebo group: 62.5 + 6.4 vs. 63.6 + 2.6 mm Hg, respectively, at 0.3 tg/kg/min (p < .05). None of the effects of fenoldopam were altered by volume status.

CONCLUSIONS

Fenoldopam increased renal blood flow in a dose-dependent manner compared with placebo, and, at the lowest dose, significantly increased renal blood flow occurred without changes in systemic blood pressure or heart rate. These findings will be useful in designing future studies exploring the role of fenoldopam in preventing or treating renal failure in patients who are not hypertensive.

Safety and pharmacokinetic profile of gadobenate dimeglumine in subjects with renal impairment

RATIONALE AND OBJECTIVES

To determine the safety and pharmacokinetics of gadobenate dimeglumine in a group of subjects with moderate or severe renal impairment.

METHODS

The safety and pharmacokinetic profile of gadobenate dimeglumine, a gadolinium (Gd3+) chelate complex in development as a contrast agent for MRI, were evaluated in a placebo-controlled, double-blind, multicenter trial. Subjects with moderate or severe renal impairment (creatinine clearances of 31 to 60 or 10 to 30 mL/min, respectively) received a 0.2-mmol/kg intravenous bolus of Gd3+ or saline placebo. Blood samples (up to 72 hours) and urine and fecal samples (up to 216 hours) were assayed for total Gd3+ content by inductively coupled plasma atomic emission spectroscopy. Gd3+ blood concentration/time data were analyzed nonparametrically and parametrically using the software program WinNonlin VI.1.

RESULTS

Mean (SD) values for Gd3+ area under the curve, blood clearance, steady-state volume of distribution, renal clearance, and creatinine clearance for the moderate group were 862 (392) micrograms.h/mL, 56 (25) mL/min, 21 (5) L, 47 (23) mL/min, and 46 (16) mL/min. Values for the severe group were 1347 (366) micrograms.h/mL, 31 (7) mL/min, 19 (6) L, 22 (7) mL/min, and 21 (8) mL/min. No Gd(3+)-related adverse events occurred. Mean values for Gd3+ recovery in urine and feces for moderate and severe groups were 74% and 6%, and 69% and 8% of the dose, respectively. Linear regression analysis demonstrated a significant relation between the level of renal function and blood clearance of Gd3+.

CONCLUSIONS

Although mean blood clearance and renal clearance values progressively declined with increasing degree of renal impairment, based on the safety profile and the fact that the administered dose was double the standard dose used for MRI purposes, there appears to be no need for dose reduction in this population.

Pharmacokinetics, safety, and tolerability of gadoversetamide injection (OptiMARK) in subjects with central nervous system or liver pathology and varying degrees of renal function

The pharmacokinetic parameters, safety, and tolerability of OptiMARK (gadoversetamide injection), a gadolinium-based magnetic resonance imaging (MRI) contrast agent, were evaluated in 163 subjects with either central nervous system (CNS) or liver pathology with and without renal insufficiency, for which a contrast-enhanced MRI was indicated. A multicenter, double-blind, randomized, placebo-controlled, parallel-group design was used in which subjects received 0.1, 0.3, or 0.5 mmol/kg of OptiMARK or placebo intravenously. Samples were analyzed for total gadolinium by inductively coupled plasma/mass spectrometry. Gadolinium pharmacokinetics were affected by renal impairment: area under the curve, half-life, and steady-state distribution volume significantly increased with declining renal function, while total body clearance decreased. In subjects with normal renal function, neither age, gender, nor liver versus CNS pathology altered gadolinium pharmacokinetics. No clinically significant changes from baseline were noted in vital signs, laboratory measures, electrocardiograms, or physical examinations. OptiMARK is safe and well-tolerated following a single intravenous injection in subjects with either liver or CNS pathology despite a prolonged elimination half-life in subjects with renal impairment.

Pharmacokinetics of flutamide in patients with renal insufficiency

AIMS

The aim of this study was to determine the pharmacokinetic parameters of flutamide, a nonsteroidal antiandrogenic compound, and its pharmacologically active metabolite, hydroxyflutamide, in renal insufficiency. Haemodialysis (HD) clearance of flutamide and hydroxyflutamide was also determined.

METHODS

Pharmacokinetic parameters were assessed for flutamide and hydroxyflutamide in 26 male subjects with normal renal function (creatinine clearance by 24 h urine collection, CLcr, greater than 80 ml min(-1) 1.73 m(-2); n=6) or reduced renal function; CLcr=50-80 (n=7), 30-49 (n=3), 5-29 (n=4), and <5 ml min(-1) 1.73 m(-2)-HD (n=6), following a single, oral 250 mg flutamide dose. Subjects undergoing HD received a second 250 mg dose of flutamide 4 h prior to HD; blood and dialysate were collected during HD to determine dialysability of flutamide and hydroxyflutamide.

RESULTS

Cmax, tmax, AUC, t1/2, and renal clearance of flutamide and hydroxyflutamide did not differ between groups. Less than 1% of the dose appeared in dialysate as hydroxyflutamide. No serious adverse events were observed.

CONCLUSIONS

Renal function did not affect flutamide nor hydroxyflutamide disposition. HD did not alter hydroxyflutamide pharmacokinetics. Dosing adjustments for renal impairment or HD are not indicated for flutamide.

A preliminary placebo-controlled crossover trial of fludrocortisone for chronic fatigue syndrome

OBJECTIVE

To provide a preliminary assessment of the efficacy and safety of fludrocortisone acetate treatment of chronic fatigue syndrome.

DESIGN

A placebo-controlled, double-blind, random-allocation crossover trial of 6 weeks of fludrocortisone.

SETTING

An outpatient clinical trials unit.

PATIENTS

Twenty-five participants with chronic fatigue syndrome (mean age, 40 years; 19 [76%] women; mean duration of illness, 7.0 years) were recruited from a research and clinic registry. Five patients withdrew from the trial.

INTERVENTIONS

All participants were scheduled to receive fludrocortisone acetate (0.1-0.2 mg) or a placebo for 6 weeks in each treatment.

MAIN OUTCOME MEASURES

Self-administered questionnaires were completed at the beginning and end of each treatment arm that asked patients to rate the severity of their symptoms on a visual analogue scale. The Medical Outcomes Study 36-Item Short-Form Health Survey, a reaction time test, and a treadmill exercise test were used to assess functional status. Blood pressure, heart rate, and plasma norepinephrine levels were obtained at baseline. Blood pressure and heart rate were recorded at the end of the exercise test and monitored at all subsequent visits.

RESULTS

At baseline, the study participants reported symptom severity greater than 5 for most symptoms, and all had evidence of marked functional impairments. No improvement was observed in the severity of any symptom or in any test of function for the 20 participants who completed both arms of the trial. Blood pressure and heart rate readings were unaffected by treatment, and plasma norepinephrine levels did not differ from those of a healthy control group. The incidence of adverse experiences was similar in the fludrocortisone and placebo arms of the trial.

CONCLUSION

Low-dose fludrocortisone does not provide sufficient benefit to be evident in a preliminary blinded trial of unselected patients with chronic fatigue syndrome.

Randomized cross-over study of adverse reactions and cost implications of intravenous push compared with infusion of iron dextran in hemodialysis patients

In many dialysis centers, iron dextran is administered by intravenous infusion rather than intravenous push (the method of administration recommended in the package insert) as a possible, but unproven, means to reduce side effects. This study was performed to determine whether there is a difference in adverse reactions between these two methods. Ten iron-deficient hemodialysis patients participated in a randomized, cross-over study of iron dextran 100 mg administered by intravenous push over 2 minutes (undiluted) or as a 30-minute intravenous infusion during the first hour of hemodialysis. Patients received a total of four doses (two by each method during four separate dialysis sessions). Blood pressure and heart rate were monitored pre-dose and at frequent intervals throughout the hemodialysis session following the dose. Patients completed adverse event surveys before and 60 minutes after the dose and prior to the next hemodialysis session. Blood pressure, heart rate, and survey data were analyzed using a Wilcoxon analysis (P </= 0.05 was considered significant). Seven patients received all four doses, two patients received only three doses (one due to missed hemodialysis session and one due to severe diarrhea possibly related to iron dextran), and one patient received only one dose (due to unstable clinical status). No differences in blood pressure, heart rate, or adverse events were observed between the two administration methods. A cost-minimization analysis was performed to compare the costs of each method of iron dextran administration. There were no differences in nursing time or number of syringes and needles used between the two methods. However, cost savings were observed with intravenous push administration because the intravenous tubing and intravenous piggyback were eliminated. Iron dextran can be administered by either intravenous push or intravenous infusion during the first hour of hemodialysis, with no significant differences between the two methods in terms of blood pressure or heart rate. Dialysis programs can minimize iron dextran administration costs by changing to the intravenous push method.