The influence of hepatic impairment on the pharmacokinetics of paliperidone.

OBJECTIVES: This study assessed the impact of hepatic impairment on the pharmacokinetics (PK) of paliperidone and its enantiomers. METHODS: A single 1 mg dose of paliperidone immediate-release (IR) was administered to subjects with moderate hepatic impairment (n = 10) and demographically matched individuals with normal hepatic function (n = 10). RESULTS: Plasma protein binding was lower in hepatically impaired subjects resulting in a 27% higher unbound fraction of paliperidone compared with healthy individuals. After correcting for the difference in plasma protein binding, unbound exposures were comparable between groups. All other PK parameters were similar between the two groups. Paliperidone IR was equally well tolerated in both groups. CONCLUSIONS: The impact of moderate hepatic impairment on paliperidone PK is not considered clinically relevant as the PK profile of unbound paliperidone is similar for subjects with moderate hepatic impairment and those with normal hepatic function. Dosage adjustments of paliperidone are not required in subjects with mild or moderate hepatic impairment.

[The effect of bile secretion on the pharmacokinetics of a theophylline sustained-release preparation]. / Einfluss einer Gallenausschüttung auf die Pharmakokinetik eines Theophyllin-Retardpräparates.

Bile excretion changes the physiological milieu of the duodenum, possibly resulting in enhanced absorption of a drug due to increased solubilisation. This possible influence of bile salts following stimulation of gallbladder emptying by the release of cholecystokinin on the pharmacokinetics of a sustained release theophylline (CAS 58-55-9) preparation (Bronchoretard) was evaluated in this study. An open, randomised, 3-way crossover study in 12 healthy, non-smoking volunteers was selected to prove or reject this hypothesis. All subjects received 500 mg of the sustained release theophylline formulation under two different cholagogia stimulating test conditions compared with a fasting reference condition. A standard breakfast and i.m. administration of cholecystokinin enabled a reproducible modulation of bile flow: a moderate and extreme contraction of the gallbladder could be induced after a standard breakfast and after i.m. administration of cholecystokinin, respectively. Following a standard breakfast, gallbladder volumes were approximately halved (50.6%) compared to the baseline volume after 79 min. Injection of 0.3 microgram/kg body weight cholecystokinin resulted in fast and complete gallbladder evacuation (94.6%) 36 min after the application of this cholagogue stimulus. Gallbladder volumes remained more or less constant under fasting conditions. This manipulation of bile flow did not influence concentration/time profiles of the sustained release theophylline preparation compared to the fasting condition. Even almost complete evacuation of the gallbladder after administration of cholecystokinin did not modify the concentration/time profile of theophylline in a relevant way. An unintentional rapid release of theophylline could be excluded for this sustained release formulation for all three treatments, as not a single case of dose dumping was observed. Furthermore, in vitro dissolution investigations using synthetic surfactants can predict neither food effects nor bile influence on the in vivo absorption at least for the sustained release formulation tested.

Effect of gallbladder contraction induced cholagogia on the pharmacokinetic profile of a sustained-release theophylline formulation.

Bile excretion might change the physiological milieu of the duodenum resulting in enhanced absorption of a drug due to increased solubilisation. This possible influence of bile salts following stimulation of gallbladder emptying via the release of cholecystokinin on the pharmacokinetics of a sustained-release theophylline (CAS 58-55-9) preparation (Bronchoretard) was evaluated in this study. An open, randomised 3-way cross-over study in 12 healthy, non-smoking volunteers was selected to prove or reject this hypothesis. All subjects received 500 mg of the sustained-release theophylline formulation under two different cholagogia stimulating test conditions and under a fasting reference condition. A standard breakfast and i.m. application of cholecystokinin enabled modulation of bile flow; a moderate and extreme contraction of the gallbladder could be induced after a standard breakfast and after i.m. application of cholecystokinin, respectively. Following a standard breakfast, gallbladder volumes were approximately halved (50.6%) compared to the baseline volume after 79 min. Injection of 0.3 micrograms/kg body weight cholecystokinin resulted in quick and complete gallbladder evacuation (94.6%) 36 min after the application of this cholagogue stimulus. Gallbladder volumes remained approximately constant under fasting conditions. This manipulation of bile flow did not influence concentration/time profiles of the sustained-release theophylline preparation compared to the fasting condition. Even almost complete evacuation of the gallbladder after application of cholecystokinin did not modify concentration/time profiles of theophylline in a relevant way. An unintentional rapid release of theophylline could be excluded for this sustained-release formulation for all three treatments, as not a single case of dose-dumping was observed. Furthermore, in vitro dissolution investigations using surfactants are neither predictive of food effects nor bile influence on in vivo absorption at least for the sustained-release formulation tested.

Pharmacokinetics of naftopidil, a novel anti-hypertensive drug, in patients with hepatic dysfunction.

The pharmacokinetics of naftopidil, a novel alpha-1 adrenoceptor-blocking antihypertensive, were investigated in ten patients (9M/1F) with hepatic dysfunction after oral administration (50 mg, tablet) and after an intravenous infusion of 5.0 mg over 2 minutes. Results were compared to a control group of 12 healthy subjects (6M/6F) of a previous investigation, which was carried out according to the identical study protocol. The pharmacokinetic parameters obtained for the i.v. administration were comparable in both groups (half life 3.6 +/- 3.4 hours in liver-impaired subjects versus 3.3 +/- 2.1 hours in controls; clearance 11.9 +/- 4.7 ml/minute/kg versus 11.0 +/- 1.6 ml/minute/kg). Following oral administration the plasma levels and half-life times of naftopidil were significantly increased in liver impairment (t1/2 16.6 +/- 19.3 hours versus 5.4 +/- 3.2 hours in controls; P = 0.012). Mean values for the absolute bioavailability in patients with hepatic dysfunction were significantly higher (mean 75%, median 53%, range 13.4-211.0%) compared to healthy subjects (mean 17%, median 16%, range 6.7-29.6%, P = 0.001). Reduction of functional hepatic blood flow in chronic liver disease or, as evidenced in one case as a consequence of shunt surgery, is the probable cause of the observed alteration in naftopidil kinetics. This phenomenon occurred only following the oral 50 mg dose whereas the intravenous 5 mg dose obviously still could be normally handled. Naftopidil demethylation and hydroxylation were both less and non-uniformly affected. The pharmacokinetic findings suggest that in patients with severe hepatic impairment or evidence for marked changes in hepatic blood flow the dose of naftopidil may require adjustment to the lower end of the therapeutic range and/or may be limited to once daily. However, before definite conclusions can be drawn, further steady-state studies are required. Despite the pharmacokinetic discrepancies no difference in drug tolerability was seen between patients and healthy subjects.

Multiple peaks and low bioavailability of furosemide correlate with the volume of fluid ingested.

Two different single dose cross-over bioavailability studies were performed comparing a new oral furosemide preparation (test preparation = preparation A) with a marketed standard with a marketed standard preparation (reference preparation = preparation B). Test and reference preparation contained 40 mg of furosemide each. Into both studies, 18 healthy male volunteers were included; 4 volunteers participated in both studies. In study 1, the volunteers ingested the tested preparations together with 300 ml of an electrolyte solution in order to substitute volume and electrolyte deficits. Additional 200 ml were given 30 min post dose, 500 ml during the next 30 min and 1000 ml during the second hour after drug intake. In study 2, the tested preparations were ingested together with 200 ml of water without any additional volume substitution. The plasma concentration curves of study 1 showed a double peaking with a first maximum of furosemide levels at 1 h and a second peak at 3 h and 4 h, respectively, on average. The concentration-time curves of study 2 showed a single peak 1 h p.a. in the mean for both preparations. The relative bioavailability of preparation A was about 67% in study 1 compared to study 2. Preparation B showed a relative bioavailability of 59% in study 1 compared to study 2.

Bioequivalence and pharmacodynamics of a modified glibenclamide formulation in healthy volunteers.

A glibenclamide preparation (Glycolande N) with a modified galenic formulation was compared with a marketed standard preparation for bioequivalence and hypoglycaemic action after single oral administration of 3.5 mg. Twelve healthy male volunteers participated in this open two-way cross-over study. The confidence intervals around the mean values of the standard preparation were all in the range of +/- 20%. No significant differences were found between both formulations for Cmax, Tmax, AUC1 and AUC3. The glucose profiles were virtually equal. Both preparations are regarded as bioequivalent and therapeutically equivalent.

Improved orthostatic dysregulation record after administration of a sustained-release form of urapidil.

The efficacy and safety of urapidil has been demonstrated in a long-term treatment. However, a relatively good record of side effects has been marred by reports of orthostatic dysregulation. This study was designed to examine the blood pressure lowering effect, tolerability and pharmacokinetics of a sustained-release formulation of urapidil. Twelve patients received either 60 mg of sustained-release urapidil (Ebrantil 60) or 50 mg urapidil for experimental reference as a fast-release tablet in single or multiple doses in a randomized, double-blind fashion. To ensure the double blind-character of the study, the tablets were encapsulated. Blood samples for the determination of urapidil (HPLC) were drawn before and at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10 and 12 h post application. Blood pressure was measured at 0.5, 1.5, 3, 8, 10 and 12 h post application. An orthostatic test was performed before and at 1, 2, 4 and 6 h post application. Twelve h after the first application, patients received a second capsule or encapsulated tablet and continued medication for two days. On day four, the same procedure as on day one was repeated, except that patients received no evening medication and blood samples and blood pressure were measured at 24, 28 and 32 h post application on the fifth day. The Cmax of sustained-release urapidil was 44% lower than for the single tablet dose and 37% lower after multiple dosing. The peak-trough fluctuation of the steady-state serum concentrations was 29% lower for the sustained-release capsule (138 +/- 45%) compared to the tablet (195 +/- 83%).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of food intake on the bioavailability of urapidil in healthy volunteers.

The influence of food intake on the pharmacokinetics of a single dose (30 mg) of urapidil in a tablet and a sustained-release capsule form were examined in 12 healthy volunteers in a double crossover trial. Drug administration under fasting conditions requires that a standardized breakfast be eaten, 4 h after drug intake. Drug application with breakfast requires drug intake with the standardized breakfast. Blood was sampled and blood pressure measured before and at 0.25, 0.5, 1, 2, 3, 4, 6, 8, 12, 15, 18, 21, 28 and 32 h after drug administration. Urapidil was determined by HPLC. AUC, Cmax, tmax and t1/2 were calculated. Food intake did not influence the bioavailability of urapidil in tablet form. After the administration of the sustained-release capsule Cmax and tmax were increased while t1/2 was decreased by food intake. Despite these differences, the AUC was not influenced by concomitant food intake with the sustained-release capsule. In the fasting state, the AUC of the sustained-release capsule was 28% lower than that of the tablet. Food intake together with the sustained-release capsule abolished this difference. Since blood pressure decreases in hypertensive patients treated with urapidil are most pronounced in the inclining part of the urapidil-serum concentration curve, maximizing this part of the curve, as is the case with the administration of the sustained-release capsule together with breakfast, should be advantageous. Therefore, the suggestion that the sustained-release capsule be taken with breakfast is of therapeutic significance.

[Bioavailability and pharmacokinetics of a new nifedipine preparation in healthy volunteers]. / Untersuchungen zur Bioverfügbarkeit und Pharmakokinetik einer neuen Nifedipin-Zubereitung an gesunden Freiwilligen.

In the course of this trial the bioavailability and the essential pharmacokinetic parameters of a newly developed 10 mg nifedipine preparation were to be determined in comparison to a marketed reference preparation after single oral administration. For this purpose, the test and the reference preparation were examined in 16 healthy volunteers according to a randomized 2-way cross-over design (latin square), blood samples were withdrawn up to 16 h p.a. and plasma concentrations of nifedipine and NPO (primary metabolite of nifedipine) were quantified by a HPLC method. Both preparations led to mean maximum concentrations of nifedipine in plasma of 110 mg/ml about 0.5 h p.a.; the mean termial half-lives were 1.8 h (test preparation) and 1.7 h (reference preparation). The data found for the metabolite NPO largely corresponded to those of the parent substance, thus equal metabolisation and adequate pharmaceutical quality of the two galenics may be presumed. Statistical comparison (ANOVA, Pratt-Wilcoxon test) did not reveal any significant differences between the test and reference preparation and, apart from a minor deviation, confidence intervals according to Westlake were sufficiently small, such that the two formulations may be considered bioequivalent. No differences of clinical relevance were detected between the two preparations in assay. The undesired side effects/concomitant symptoms known after nifedipine administration were observed.

Pharmacodynamics and pharmacokinetics of urapidil in hypertensive patients: a crossover study comparing infusion with an infusion-capsule combination.

The pharmacokinetics and haemodynamic effects of infused urapidil and an infusion-capsule combination were followed to study the correlation between the serum urapidil level and the blood pressure. Prior to urapidil administration, basal blood pressure and heart rate were measured for 16 h in 12 male hypertensive patients. Six patients received infusions lasting for 4 h of urapidil 10, 2.5 and 5 mg/h. Six patients were infused with urapidil 10 mg/h for 4 h and 2 h after the end of the infusion each took a 60-mg capsule. After a 5 day washout period the procedures were crossed over. A maximum serum urapidil level of 625 +/- 232 ng/ml was achieved at the end of the 10 mg/h infusion, when the fall in blood pressure was 37/21 mmHg. During the 2.5 and 5 mg/h infusions the serum urapidil level was 330 and 420 ng/ml, respectively, and the corresponding decreases in blood pressure were 28/16 mmHg and 31/8 mmHg. Although the urapidil concentration 1 hour after beginning the infusion was only 184 +/- 89 ng/ml a near maximal blood pressure decrease had already occurred 33 +/- 9/20 +/- 8 mmHg, whereas, 1 h after the end of the infusion the reduction in blood pressure was only 10 +/- 12/3 +/- 8 mm, with a urapidil concentration of 358 +/- 120 ng/ml. During the plateau phases of both the infusion and infusion-capsule treatments the falls in blood pressure followed the serum urapidil levels. Only in the initial rising and final falling phases of the treatments were the pharmacodynamics and pharmacokinetics of urapidil not correlated.

[The pharmacokinetics and bioavailability of urapidil. In vitro/in vivo correlations of different experimental formulations]. / Zur Pharmakokinetik und Bioverfügbarkeit von Urapidil. In-vitro-/in-vivo-Korrelation verschiedener experimenteller Zubereitungen.

The pharmacokinetic parameters, including the relative bioavailabilities of two experimental batches of a 60-mg urapidil slow release-capsule and a 30-mg urapidil drinking ampoule (Ebrantil) had to be evaluated in a randomized, three-period change-over study with 12 healthy volunteers after single dosing. The appropriate parameters for the capsule formulations were compared with their dissolution rates obtained by different in vitro models. The capsules showed different half-change, but comparable single-fluid dissolution profiles. Both batches of the capsules showed equivalence with respect to the extent of absorption, in connection with 100% relative bioavailability on average. A correlation of the in vivo parameters Tmax and Cmax with the half-change model can be assumed.

Pharmacokinetic profile of metaclazepam (Talis), a new 1.4-benzodiazepine. Influence of different dosage regimens on the pharmacokinetic profile of metaclazepam and its main metabolite under steady-state conditions.

The pharmacokinetic parameters of the new 1.4-benzodiazepine metaclazepam (Talis) were investigated. In particular, the question of whether the drug and/or its main metabolite accumulates in the body under steady-state conditions was studied. Two dosage regimens were compared by a randomized two-way crossover design: a once-a-day dosing (15 mg metaclazepam in the evening, = A) versus a twice-a-day dosing (5 mg in the morning plus 10 mg in the evening, = B) over ten days in twelve healthy male volunteers. Plasma levels of metaclazepam and its major biotransformation product, N-desmethylmetaclazepam, were determined. Comparing the treatments, significant differences were found for Cmax, but not for AUC-3 and Tmax. These results are also valid for the comparison of days 1 and 10 of each treatment. Higher Cmax values for dosage regimen A were found but Tmax and Cl/F remained stable in both treatments taking into account that 12 hours after the first medication, another dosing took place in treatment B. Eight hours after application, plasma levels were markedly low, Cmax values after single-dosing were nearly twice as high as after multiple dosing. Therefore based on these pharmacokinetic findings, a second dosing seems to be necessary; the clinical relevance needs further investigation. It has been reported, in fact, that it is in general very difficult to demonstrate a correlation between blood levels and therapeutic effects for 1.4-benzodiazepines (1,2).

Pharmacokinetics and bioavailability of three different galenic nifedipine preparations.

In a randomized three-way crossover study with twelve volunteers the bioavailability and main pharmacokinetic parameters of three different galenic formulations of nifedipine (hard gelatine capsule with pellets = preparation A, soft gelatine capsule with liquid nifedipine = preparation B, retard-tablet = preparation C) were determined. Plasma concentrations of nifedipine were measured by capillary gas-liquid chromatography up to 24 h after single dosing as well as up to 48 h after multiple doses of the drugs (steady state). Statistically significant differences between the preparations were found for AUC, Cmax, and Tmax. In all respects preparation A was intermediate to the other preparations. Plasma levels of 40 ng/ml or more were reached for most subjects within the first half hour after application of a single dose of preparation A and under steady state conditions plasma concentrations of 25 ng/ml or more could be upheld with this preparation for a longer time than with the reference retard tablet (preparation C). No accumulation of nifedipine in plasma occurred following multiple dosing.

Comparison of the pharmacokinetic profile of metaclazepam in old and young volunteers.

A single-centre, open, Phase I-study comparison of the pharmacokinetics of a single dose of metaclazepam 10 mg, a new 1,4-benzodiazepine has been done in 10 older and 20 younger volunteers. No important age-related effect was found on the kinetics of metaclazepam or its N-desmethyl derivative, the principal metabolite in man.

[Comparative studies on the tolerance of bioequivalent doses of intravenous methylxanthine preparations in healthy subjects]. / Vergleichende Untersuchungen zur Verträglichkeit bioäquivalenter Dosen intravenöser Methylxanthin-Zubereitungen bei gesunden Probanden.

In a comparative tolerance study with two different intravenous methylxanthine preparations, a theophylline-ethylendiamine preparation (TE-reference preparation) was tested against a combination of theophylline, proxyphylline (7-(2-hydroxypropyl)-theophylline) and diprophylline (7-(2,3-dihydroxypropyl)-theophylline) (Neobiphyllin; TPD = test preparation) in 10 healthy volunteers by a single blind cross-over design. Both preparations were infused under continuous control of vital parameters (blood pressure, pulse, respiration frequency, heart rhythm) as infusions (1 ampoule with 800 mg TPD or 1 short-infusion with 480 mg of TE for 20 min, each) up to the individual tolerance limit or the pre-defined limit of 3 ampoules/short infusions, respectively. The maximum tolerated infusion time and the serum levels at which the first side-effects appeared, were compared. These maximum doses could be administered to 6 volunteers under TPD, but only to two under medication with the reference preparation. Side-effects under TPD occurred in 5, after infusion of the reference preparation in 9 volunteers. Serum levels of theophylline at the end of the infusion period reached (14.6 +/- 4.21 (TPD) and 23.01 +/- 6.02 mg/l (TE), respectively. The average infusion time for the test preparation was 54.8, for the reference preparation 46.2 min. The average serum theophylline levels of the 5 volunteers with side-effects under TPD reached--when these side-effects occurred --11.26 +/- 4.52 mg/l; the same volunteers showed after administration of TE levels of 14.94 +/- 7.49 mg/l. Our results showed an approx. additive effect of the side-effects together with an--according to literature--over-additive pharmacological effect of the single components of TPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of muzolimine and indapamide during treatment for essential hypertension.

Muzolimine, a new saliuretic, has been shown to combine high ceiling and long-acting effects in animal experiments. This study was designed to examine whether this desirable combination of effects, which up until the present time has not been incorporated into any substance also occurs during patient treatment. Fifty-three patients with mild essential hypertension (WHO groups I and II) in three medical centers were treated with either muzolimine or indapamide, which served as the reference preparation, in a randomised, double-blind study. After a two week run-in phase during which the patients received placebo, half of the patients received 20 mg muzolimine and the other half 2.5 mg indapamide once daily. Eight weeks of therapy were followed by a 2 week follow-up phase, during which placebo was dispensed. During the trial period a weekly clinical examination was performed including the measurement of blood pressure, pulse, hematocrit, electrolytes, uric acid, glucose, creatinine and lipid status. An electrocardiogram and Schellongtest were conducted every two weeks. Patients were instructed to keep a diary in which they were to note drug related complaints. Statistical analysis was carried out using the Pratt-Wilcoxon Pair Test. Differences were judged significant at the 5% level. Both muzolimine and indapamide were tolerated well with minimal side effects, which however, did not make it necessary to discontinue treatment. Both preparations induced mild blood pressure reductions of approximately 10 and 5 mmHg for the systolic and diastolic blood pressure, respectively. Two weeks after cessation of muzolimine treatment neither systolic nor diastolic blood pressure showed any significant difference to values achieved during the treatment phase.(ABSTRACT TRUNCATED AT 250 WORDS)

[Bioavailability of new nifedipine preparations in man. 1. Pharmacokinetics of nifedipine in the form of sustained-release tablets]. / Bioverfügbarkeit von neuen Nifedipin-Zubereitungen beim Menschen. 1. Mitteilung: Pharmakokinetik von Nifedipin in Form von Retardtabletten.

Following a single dose of a 20 mg nifedipine retard-tablet (Pidilat retard or a marketed formulation) to 12 healthy volunteers in a randomized, two-fold cross-over trial the nifedipine plasma levels were quantitatively determined by gas chromatography up to 24 h p.a. The relative bioavailabilities and important pharmacokinetic parameters were calculated and then statistically evaluated for significant differences between the preparations. Approx. 2 h after dosing, peak concentrations of 13 to 74 ng/ml were reached, the minimal therapeutic plasma level of 10-15 ng/ml was - in general - upheld for 10 respectively 8 h. Terminal elimination half-lives were calculated to be 5 and 8 h, respectively. An extrapolation with the obtained data for the expected steady state plasma levels after a twice-a-day dosing showed that the above mentioned therapeutically relevant plasma levels of the unchanged drug are in general achieved for most of the dosage interval. The strong inter- and intraindividual variations of blood levels after nifedipine application, which have already been described by numerous other authors, could also be observed in this study.