Plasma and urine pharmacokinetics of niacin and its metabolites from an extended-release niacin formulation.

OBJECTIVE: To characterize plasma and urine pharmacokinetics of niacin and its metabolites after oral administration of 2,000 mg of extended-release (ER) niacin in healthy male volunteers. METHODS: Niacin ER was administered to 12 healthy male subjects following a low-fat snack. Plasma was collected for 12 h post dose and was analyzed for niacin, nicotinuric acid (NUA), nicotinamide (NAM) and nicotinamide-N-oxide (NNO). Urine was collected for 96 h post dose and analyzed for niacin and its metabolites, NUA, NAM, NNO, N-methylnicotinamide (MNA) and N-methyl-2-pyridone-5-carboxamide (2PY). RESULTS: Mean niacin Cmax and AUC(0-t) values were 9.3 microg/ml and 26.2 microg x h/ml and were the highest of all analytes measured. Peak niacin and NUA levels occurred at 4.6 h (median) while tmax for NAM and NNO were 8.6 and 11.1 h, respectively. The mean plasma terminal half-life for niacin (0.9 h) and NUA (1.3 h) was shorter as compared to NAM (4.3 h). Urine recovery of niacin and metabolites accounted for 69.5% of the administered dose; only 3.2% was excreted as niacin. The highest recovery was for 2PY (37.9%), followed by MNA (16.0%) and NUA (11.6%). Mean half-lives for 2PY and MNA calculated in urine were 12.6 and 12.8 h, respectively. CONCLUSIONS: Niacin was extensively metabolized following oral administration, and about 70% of the administered dose is recovered in urine in 96 h as niacin, NUA, MNA, NNO, NAM and 2PY. The plasma levels of the parent niacin were higher than its metabolites though only about 3% of the unchanged drug is recovered in urine.

Aspirin reduces cutaneous flushing after administration of an optimized extended-release niacin formulation.

OBJECTIVE: Niacin is an effective treatment for dyslipidemia due to its favorable effects on multiple lipid parameters. Clinical utility of niacin is sometimes limited, however, because of cutaneous flushing. A once-daily, extended-release (ER) niacin formulation has been shown to significantly reduce flushing compared to immediate-release niacin. An optimized (reformulated) version of niacin ER has recently been developed and was shown in a previous study to significantly reduce flushing intensity (severity) compared to the non-optimized (commercial) formulation. The current study was designed to evaluate the effect of aspirin on various indices of flushing when administered with the optimized niacin ER formulation. METHOD: This was a randomized, double-blind, double-dummy, placebo-controlled flush provocation crossover study in healthy males. To increase the probability of flushing, subjects received a single dose of reformulated niacin ER 2,000 mg, which is the upper limit of the approved dosage range. Subjects received 650 mg aspirin orally either 30 minutes before or concomitantly with niacin ER, or placebo with niacin ER, in 3-way crossover fashion. The primary endpoint was the number of subjects who reported at least one flushing event. Secondary endpoints included the perceived intensity and duration of flushing symptoms. RESULTS: In the 148 men who completed all treatments, aspirin significantly reduced flushing incidence (the primary endpoint) following administration of niacin ER compared with placebo. Among subjects receiving placebo, 77% of subjects reported flushing with niacin ER. Among subjects receiving aspirin, 53-61% of subjects reported flushing (pretreatment and concomitant treatment, respectively, both p < 0.001 compared with placebo) with niacin ER. Aspirin also significantly reduced intensity and duration of flushing (by 30-40%) compared with no aspirin. The two aspirin-containing treatments (i.e. pre- or concomitant treatment) were similar in their effects on flushing incidence, intensity and duration. Median intensity on a 100 mm visual analogue scale (VAS) was reduced from 33 mm with placebo to 19-23 mm with aspirin. Median duration was reduced from approximately 1 hour with placebo to 37-48 minutes with aspirin. CONCLUSION: Aspirin significantly reduced the incidence, intensity and duration of flushing associated with reformulated niacin ER. These results support the administration of aspirin prophylactically to decrease niacin-induced cutaneous flushing and to improve patient adherence and acceptability of chronic niacin treatment at therapeutic doses.

Improved control of niacin-induced flushing using an optimized once-daily, extended-release niacin formulation.

INTRODUCTION: Niacin is a recognized treatment for dyslipidemia due to its favorable effects on all lipid parameters. However, the clinical use of niacin has been limited by its adverse effects, particularly cutaneous flushing. A newly reformulated 1,000 mg niacin ER tablet has been designed to reduce flushing relative to the original commercial niacin ER formulation. The aim of this study is to compare the incidence, intensity and duration of flushing between the 1,000 mg reformulated niacin ER and the 1,000 mg commercially available formulation, when administered as a single 2,000 mg dose to healthy male volunteers. METHODS: This was a double-blind, double-dummy, placebo-controlled, 3-way crossover, flush provocation study conducted at a single center. To increase the probability of flushing, subjects were administered niacin ER at the upper limit of the approved dosage range (2,000 mg), and were precluded from using aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) during the study. Subjects received reformulated niacin ER, commercial niacin ER or placebo in a 3-way crossover fashion. The primary flushing variable was the occurrence of a flushing event. Secondary flushing variables included the number of flushing episodes, intensity and duration of flushing for both overall flushing events and for individual symptoms of flushing (redness, warmth, tingling and itching). RESULTS: A total of 156 subjects were enrolled in the study. Of 133 subjects who received at least 1 dose of study medication in at least 2 study periods, 89% of subjects experienced flushing during treatment with reformulated niacin ER, and 98% of subjects experienced flushing during treatment with commercial niacin ER. This difference was statistically significant (p - 0.0027). Reformulated niacin ER resulted in a 42% reduction in median flush intensity (p < 0.0001) and a 43% reduction in median flush duration (p < 0.0001) relative to commercial niacin ER. The duration of first flushing event was more than 1 hour shorter with reformulated niacin ER. During the study, 29% of subjects (45/156) experienced treatment-emergent adverse events, which were mostly mild in intensity and considered to be remotely related or unrelated to the study drug. CONCLUSION: The 1,000 mg reformulated niacin ER tablet substantially decreases the incidence, intensity and duration of flushing relative to the commercially available 1,000 mg niacin ER tablet, and represents an improved niacin therapy option.

Efficacy of once daily extended-release theophylline in decreasing the use of inhaled beta 2-agonists in stable, mild-to-moderate asthma patients.

BACKGROUND/OBJECTIVE: The purpose of this study was to determine whether the addition of extended-release theophylline to the daily treatment regimen of inhaled beta 2-agonist users would result in decreased use of beta 2-agonist while maintaining similar efficacy for treatment of asthma. METHODS: This was a single-blind, multicenter (six sites) study. Sixty-one patients with a history of mild-to-moderate asthma treated with inhaled beta 2-agonist were randomized to treatment with Theo-24 (anhydrous extended-release capsules) plus inhaled beta 2-agonist or placebo plus beta 2-agonist. Patients kept daily symptom diaries, measured peak flow rates, recorded puffs of inhaled beta 2-agonist, and adverse events during a 4-week treatment period. RESULTS: Fifty-five patients were included in the efficacy analysis. The primary efficacy variable in this study was the mean number of puffs (adjusted for baseline differences) of beta 2-agonist inhaled per day. In this study, the addition of theophylline to the daily regimen of inhaled beta 2-agonist for 4 weeks significantly reduced the total daily dose of inhaled beta 2-agonist at weeks 3 and 4 of treatment compared with placebo. The differences were significant at the P < .05 level. For patients in the theophylline group, the number of puffs decreased from an unadjusted mean of 9.81 at baseline to an adjusted mean of 6.78 after 4 weeks of treatment compared with 9.91 at baseline and 8.17 for the placebo group. There were no unexpected or serious adverse events. CONCLUSIONS: In this study, the addition of once daily, extended-release theophylline to the daily regimen of inhaled beta 2-agonist for 4 weeks significantly reduced the total daily dose of inhaled beta 2-agonist at weeks 3 and 4 of treatment compared with placebo, while maintaining acceptable asthma symptom scores.

Pharmacokinetic study of zeolite A, sodium aluminosilicate, magnesium silicate, and aluminum hydroxide in dogs.

Zeolite A is a synthetic zeolite which may have therapeutic utility in osteoporotic individuals because of its ability to stimulate bone formation. A study of Zeolite A (30 mg/kg), sodium aluminosilicate (16 mg/kg), magnesium trisilicate (20 mg/kg), and aluminum hydroxide (675 mg) was designed in beagle dogs. The purpose of this study was to compare the oral bioavailability of silicon and aluminum from Zeolite A, sodium aluminosilicate, magnesium trisilicate, and aluminum hydroxide in dogs. Twelve female dogs received each compound as a single dose separated by one week in a randomized, 4-way, crossover design. Plasma samples were drawn at time 0 and for 24 hours after dosing. The concentrations of silicon and aluminum were determined by graphite furnace atomic absorption. The mean plasma silicon AUC values (+/- S.D.) were 9.5 +/- 4.5, 7.7 +/- 1.6, 8.8 +/- 3.0, 6.1 +/- 1.9 mg.hr/L and the mean plasma silicon Cmax values (+/- S.D.) were 1.07 +/- 1.06, 0.67 +/- 0.27, 0.75 +/- 0.31, 0.44 +/- 0.17 mg/L for Zeolite A, sodium aluminosilicate, magnesium trisilicate, and aluminum hydroxide respectively. Although mean silicon AUC and Cmax values were elevated when compared to baseline after administration of the silicon containing compounds, only the AUC from Zeolite A reached statistical significance (p = 0.041). The mean plasma silicon Tmax values (+/- S.D.) were 7.9 +/- 6.4, 5.8 +/- 4.6, 6.9 +/- 6.3 and 8.5 +/- 3.4 hrs for Zeolite A, sodium aluminosilicate, magnesium trisilicate and aluminum Hydroxide respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic study of (S)-(-)-2-(N-propyl-N-(2-thienylethyl)amino)-5-hydroxytetralin infusion in cynomolgus monkeys.

A pharmacokinetic study of the dopamine D2 receptor agonist (S)-(-)-2-(N-propyl-N-(2-thienylethyl)amino)-5-hydroxytetralin+ ++-HCl (N-0923) infused in female cynomolgus monkeys over a 4-h period was carried out at International Research and Development Corporation. The purpose of this study was to estimate the elimination half-life and elucidate the dose-clearance relationship in cynomolgus monkeys with a randomized three-way crossover intravenous (iv) infusion study design. Six female cynomolgus monkeys were dosed by iv infusion for 4 h with 0.1, 0.5, and 1.0 mg/kg/h. Plasma samples were drawn during the infusion and up to 4 h post infusion. The plasma concentrations were determined by a sensitive and specific HPLC assay with electrochemical detection after solid-phase extraction at the Department of Toxicology and Bioanalysis at the University Center for Pharmacy in Groningen, The Netherlands. The plasma data were best described by a two-compartment open model. Mean elimination half-lives of 36.8, 39.6, and 52.4 min and mean clearance values of 229 +/- 35, 202 +/- 85, and 191 +/- 36 mL/min/kg were obtained for doses of 0.1, 0.5, and 1.0 mg/kg/h, respectively. The steady-state volumes of distribution were estimated as 3.89 +/- 0.816, 3.53 +/- 1.62, and 4.70 +/- 3.67 L/kg for the same doses, respectively. There were no significant differences between any of the estimated pharmacokinetic parameters for any of the infusion doses. Clearance was not dose dependent and steady-state plasma concentration appeared directly proportional to dose, suggesting linear pharmacokinetics in this dose range for monkeys.

Comparative steady-state bioavailability of Theo-24 and Theo-Dur in healthy men.

This study was designed to compare the steady-state theophylline serum concentrations produced by 800 mg daily doses of Theo-24 and Theo-Dur in normal, healthy men administered according to each product's recommended dosing instructions. Sixteen subjects with theophylline clearances ranging from 0.39 to 0.95 mL/min/kg (average, 0.60 mL/min/kg) and theophylline elimination half-lives ranging from 5.1 to 10.5 hours (average 7.9 hours) completed the study. They were all nonsmokers, who ranged in age from 18 to 44 years and were within 10% of normal weight for their height and build. Theo-24 demonstrated a high extent of absorption (89%, range 54% to 115%) relative to Theo-Dur. Both formulations demonstrated similar times to maximum theophylline concentration (11.3 hours for Theo-24 and 11.5 hours for Theo-Dur), similar peak to trough concentration ratios relative to the trough concentration (74% for Theo-24, 62% for Theo-Dur) and similar periods of time within 5 to 15 mg/L (25.2 to 75.7 mumol/L; 21.4 hours for Theo-24, 19.4 hours for Theo-Dur). No "dose dumping" was demonstrated. The results indicate that Theo-24 dosed at least one hour prior to a high-fat breakfast produces serum theophylline concentrations in a range similar to Theo-Dur administered every 12 hours.

Pharmacokinetic comparison of flurbiprofen in end-stage renal disease subjects and subjects with normal renal function.

This study compared the pharmacokinetics of flurbiprofen (F) and three major metabolites in patients with end-stage renal disease (ESRD) undergoing continuous ambulatory peritoneal dialysis (CAPD) with the pharmacokinetics of F in normal subjects. A single 100-mg dose of F was administered to each of nine normal subjects and eight ESRD subjects. Blood and urine samples were collected in both groups; serial and end of dwell dialysate samples were obtained from the ESRD subjects. Plasma was analyzed for both the R and S optical isomers of F and its major metabolite, 4'-hydroxy-flurbiprofen (HF). Urine and dialysate were analyzed for F and three known metabolites. Plasma concentrations of F in the ESRD subjects were approximately 50% of the values obtained from the normal subjects (P less than .05). Flurbiprofen half-life and Tmax were not different. Elimination of HF was reduced in ESRD subjects. Urinary data suggest that HF was the major metabolite excreted (36% of the dose) in normal subjects whereas 3',4'-dihydroxy-flurbiprofen was the major metabolite (9% of the dose) excreted in the ESRD group. Mean urinary recovery of the dose was 73% in the normal subjects, but only 16% in ESRD subjects. Neither F nor its metabolites were detected in dialysate. Small enantiomer differences were seen. This study suggests that ESRD subjects have lower plasma levels of F than normal subjects when administered equal size doses. Accumulation of metabolites may occur in ESRD subjects upon multiple dosing. Enantiomer differences are not clinically significant.

Stability of diltiazem in different biological fluids.

The hydrolysis of diltiazem in biological fluids: whole blood, plasma, and gastric fluid was investigated under conditions considered close to the physiological situation. The most significant rate of hydrolytic degradation was found in whole blood (half-life of 27 h), followed by plasma (half-life of 88 h), while the least significant degradation rate was observed in gastric fluid (half-life 153 h). The kinetic profiles of diltiazem hydrolysis indicate that hydrolytic degradation in the biological fluids makes a minimal contribution to the clearance and disposition of the drug.

Comparative pharmacokinetics of azlocillin and piperacillin in normal adults.

The single-dose pharmacokinetics of azlocillin and piperacillin were compared by using a randomized, crossover design. The concentrations of azlocillin in serum were consistently higher than those of piperacillin throughout an 8-h study. The area under the time-concentration curve of azlocillin was significantly greater than that of piperacillin, and the total body clearance of azlocillin was significantly lower than that of piperacillin.