Effect of linagliptin (BI 1356) on the steady-state pharmacokinetics of simvastatin.

OBJECTIVE: This study was conducted to investigate any potential effect of the dipeptidyl peptidase-4 inhibitor linagliptin (which is being developed to improve glycemic control in patients with Type 2 diabetes) on the pharmacokinetics of simvastatin (a lipid-lowering, HMG-CoA reductase inhibitor). METHODS: This open-label, multiple-dose study was conducted in 20 healthy male Caucasian subjects. Simvastatin (40 mg/day) was administered alone for 6 days, followed by co-administration with linagliptin (10 mg/ day) for 6 days, followed by simvastatin single administration for a further 8 days. Plasma concentrations of simvastatin and its active metabolite simvastatin beta-hydroxy acid were determined on Day 6 (before co-administration of linagliptin) and Days 12, 16 and 20 (after co-administration of linagliptin). RESULTS: The geometric mean ratio (GMR) (90% confidence interval (CI)) following co-administration of linagliptin with simvastatin (Day 12) compared with administration of simvastatin alone (Day 6) for simvastatin AUC was 134.2% (119.4, 150.7) and for simvastatin acid AUC was 133.3% (118.1, 150.3). The GMR (90% CI) for simvastatin Cmax,ss was 110.0% (89.3, 135.6) and for simvastatin acid Cmax,ss was 120.7% (101.5, 143.6). 20 adverse events were reported by 11 subjects. Both simvastatin and linagliptin were well tolerated. CONCLUSIONS: Linagliptin-mediated effects on simvastatin exposure are not considered to be clinically relevant in terms of patient tolerability or safety. Therefore, a dose adjustment of linagliptin is not necessary when these two agents are administered together and linagliptin co-administration is not expected to exert a clinically relevant effect on the pharmacokinetics of other CYP3A4 substrates.

Pharmacokinetics and pharmacodynamics of the dual FII/FX inhibitor BIBT 986 in endotoxin-induced coagulation.

BIBT986 is a dual inhibitor of factors Xa and IIa. The aim of this study was to compare with placebo the effect of three doses of BIBT986 on coagulation, platelet activation, and inflammation. This was a prospective, randomized, double-blind, placebo-controlled, parallel-group dose escalation trial in 48 healthy male volunteers. Participants received one of three doses of BIBT986 or placebo intravenously together with a bolus infusion of 2 ng/kg lipopolysaccharide (LPS). BIBT986 dose-dependently changed global coagulation parameters and in vivo markers of thrombin generation and action: BIBT986 doses, which prolonged activated partial thromboplastin time by 100%, completely suppressed the LPS-induced increases in prothrombin fragment, thrombin-antithrombin complexes, and D-dimer, which were 6.1-, 14.5, and 3.5-fold in the placebo group, respectively. BIBT986 did not influence inflammation, fibrinolysis, or platelet activation. Therefore, BIBT986 is a potent anticoagulant in the human endotoxemia model.

Pharmacokinetics and pharmacodynamics of BIBT 986, a novel small molecule dual inhibitor of thrombin and factor Xa.

BACKGROUND: Current anticoagulant development focuses on agents with predictable pharmacokinetic and pharmacodynamic (PD) properties. BIBT 986 is a novel potent anticoagulant with a dual mechanism of action: it competitively inhibits factor (F) Xa and FIIa. AIMS: To determine the safety, tolerability, pharmacokinetics (PK) and PD of BIBT 986 following intravenous infusion in healthy male volunteers. METHODS: In three randomized, double-blind, placebo-controlled trials, subjects were administered by intravenous infusion escalating doses of BIBT 986 for up to 32 h. BIBT 986 concentrations were determined in plasma and urine samples by high pressure liquid chromatography tandem mass spectrometry. Pharmacodynamic response was assessed by measuring the changes in blood coagulation times. Activated partial thromboplastin time, International Normalized Ratio, thrombin time and ecarin clotting time were determined and compared with baseline results. RESULTS: In all three studies, intravenous infusion of BIBT 986 was safe and well tolerated. BIBT 986 exhibited linear PK over the dose range tested. Clearance was about 8 L h(-1) and V(ss) about 50 L. Apparent steady state concentrations were reached within 24 h, indicating a dominant half-life of about 6 h. The terminal half-life of BIBT 986 was approximately 12 h. Renal excretion contributes approximately 50% to total elimination. Overall interindividual variability in pharmacokinetic and PD parameters was < 40%. There was a linear correlation between plasma concentrations and PD responses, suggesting excellent predictability. CONCLUSION: BIBT 986 is the first small molecule of a novel class of anticoagulants that potently and directly inhibits both coagulation FXa and thrombin. It has predictable pharmacokinetic and PD characteristics.

Restricted food access and light-dark: impact of conflicting zeitgebers on circadian rhythms of the rabbit.

Free-running circadian rhythms of rabbits were exposed to a 11:55-11:55-h light-dark (LD) schedule. After complete entrainment (63 +/- 22 days), the predominantly nocturnally active rabbits were exposed to an additional zeitgeber, restricted food access (RF), which was imposed during the light period. In five animals RF had the same period (T) as the LD cycle (23:50 h), and in five other animals TRF was 24:10 h. At a period of 23:50 h for both zeitgebers, the rhythms of four animals were stably entrained to RF, while in one animal a component of the rhythm broke away from RF and entrained to the LD zeitgeber. In animals exposed to zeitgebers of different periods most of the activity rhythm also entrained to RF, but 20 +/- 7% of the activity entrained to the LD zeitgeber. The light-entrained activity component merged with the RF component when the zeitgebers crossed, and decomposition occurred when the phase difference exceeded 4-6 h. The results indicate that two circadian oscillator systems exist in the rabbit, one entrained by light-dark cycles and the other by feeding-fasting cycles. Both exert common control over a number of overt behavioral rhythms.

Circadian rhythms of rabbits during restrictive feeding.

Without a zeitgeber the circadian rhythms of five physiological functions free-ran with a period length greater than 24 h. Restricted feeding time (RF) masked the free-running rhythms. In addition to masking, entrainment with RF occurred. This process was most evident in locomotor activity and visits to the food box. RF thus had zeitgeber properties in these rabbits. However, in most rabbits the RF zeitgeber was not strong enough to entrain the circadian rhythm completely. A small component free-ran during RF. Following return to continuous food access the whole circadian rhythm resumed to free-run again. In some animals its phase was determined by the RF zeitgeber and in others by the small free-running fraction present during RF. The results suggest that in addition to the light-dark-entrainable circadian oscillator system a feeding-entrainable oscillator exists that takes over phase control of the majority of the rhythm during RF.

Structure-activity relationship in clonidine-like 2,3-disubstituted 2-aryl-imino-imidazolidines.

In anaesthetized rabbits the hypotensive activity of a group of 2,3-disubstituted 2-aryl-imino-imidazolidines was estimated. Compounds with 3-bromo substituents at the phenyl moiety of the molecule are more than or as active as clonidine. Correlations between blood pressure lowering effect and lipophilicity, maximum alpha-adrenergic effects (alpha E') and -log ED50 (pD2') of blood pressure increase in spinalized rats and pKA were calculated. The results show a positive linear correlation between as well partition coefficient as alpha E' and hypotension. The relationship between pD2' and hypotensive. effect is less prominent. pKA seems to have no influence on the blood pressure effects of these compounds.

The internal synchronization of five circadian functions of the rabbit.

Five different physiological functions of the rabbit (hard faeces and urine excretion, food and water intake and locomotor activity) were registered during LD 12:12 and during continuous light conditions (LL). (1) In LD 12:12 a strong synchronization of the five parameters existed. The minima of all functions consistently occurred during the hours of light. The nocturnal percentage of overall 24-hr events was increased significantly in 'hard faeces excretion' (66 +/- 8(S.D.)%), 'water intake' (64 +/- 15(S.D.)%) and 'urine excretion' (58 +/- 10(S.D.)%). The nocturnal percentage of locomotor activity was significantly increased during the dark-hours in 9 out of 14 animals. In the other five individuals prominent peaks were present even during the photoperiod. On the average of all 14 animals 55 +/- 13(S.D.)% of the 24 hr events of locomotor activity occurred during the night. Despite a trough during the cessation of hard faeces excretion the events of food intake were not elevated significantly during the dark hours. (2) During LL the synchronization of the five functions within each animal persisted during the complete 90-day LL period. A free-running circadian rhythm with tau = 24.8 +/- 0.5(S.D.) hr was present in the four rabbits kept in LL conditions within 5-16 days after the withdrawal of the zeitgeber. (3) In addition to the circadian period the power spectrum analysis of data obtained during LD 12:12 revealed significant ultradian periods of an average period length of 11,6 hr (hard faeces and urine excretion), 8 hr (food and water intake, locomotor activity) and 4 hr (food intake, locomotor activity). During the free-run ultradian periods of 8 and 3.2-4.2 hr were significant in almost all parameters. (4) During LL the level of locomotor activity was reduced for 13 +/- 16(S.D.)%, the events of food intake were increased for 17 +/- 12(S.D.)%. (5) The reinserted LD 12:12 zeitgeber re-entrained the circadian rhythms within 25-45 days. (6) These results provided evidence of a predominant nocturnality of the rabbits under investigation.

Development of a RIA for clonidine and its comparison with the reference methods.

A radioimmunoassay for clonidine was optimized by introducing, as a tracer ligand, an iodinized clonidine derivative specifically labeled with more than 500 Ci/mMol. The detection limit of clonidine was 10 pg/ml. The high assay specificity was demonstrated by a double isotope technique. The intraassay coefficient of variance (VK) was less than 4% for any concentration, the interassay VK did not exceed 8.3%. The assay reliability was increased when the plasma samples were diluted 1:5, prior to analysis, in normal human blood plasma, which was also used for the preparation of the calibration samples. In a comparative manner, this assay system was subjected to double-blind accuracy control tests, including all other reference methods so far described for clonidine analysis in blood plasma samples. The RIA technique presented here turned out to be the most sensitive and most reliable method, requiring, moreover, the smallest volumes of blood plasma (0.05 ml). This procedure was appropriate for routine tests, since one technician could perform 500 sample analyses a day. The advantages and disadvantages of each method are discussed.

Development and quality control of a highly sensitive radioimmunoassay for alinidine.

A new precise and sensitive radioimmunoassay (RIA) for alinidine (N-allyl-clonidine) has been developed. Synthesis and analysis of the hapten (4-carboxy-alinidine = STH 2329), as well as the production of the antibody in rabbits, are described in detail. At a final dilution of 1 : 1000, the resulting immune serum binds 50% of a tritiated alinidine standard (50 pg). The detection limit of the present RIA for alinidine is 50 pg/ml plasma. The intra-assay coefficient of variance (VC) is lower than 4% (N = 10) for any standard concentration; the inter-assay VC does not exceed 8.7%. There is no cross reactivity of any alinidine metabolite or congener with the antibody. The low detection limit of the assay, 10(-3) of therapeutically relevant alinidine blood levels, brings about several analytical advantages, which are discussed in detail. Quality control tests were performed in comparison with two reference methods (HPLC). Concerning assay sensitivity, specificity, reliability, and expenditure in costs or sample volumes, the RIA turned out to be the optimal method for routine analysis of alinidine in biological fluids. An example for practical use of the assay is given, evaluating the pharmacokinetics of alinidine in beagle dogs. From the accumulated renally-excreted total radioactivities, the enteral absorption of the drug was calculated (91%); the bioavailability of orally administered alinidine was derived from the corresponding areas under the blood plasma concentration curves of the radioimmunologically-evaluated parent compound (72%).

Chemistry, pharmacology, and structure-activity relationships with a new type of imidazolines exerting a specific bradycardic action at a cardiac site.

The reaction of alkyl halides with 2-(arylimino)imidazolidines (I) leads to imidazoline derivatives II, in which the side chain is situated at the bridge nitrogen atom between the phenyl group and the imidazoline ring. The new imidazolines (II) exert a specific bradycardic action at a cardiac site. Syntheses and pharmacology are shown and structure-activity relationships discussed. The results reveal that the imidazoline derivatives (II) represent a class of compounds with a novel type of cardiac action.

A newly developed precise and sensitive radioimmunoassay for clonidine.

A new precise and sensitive radioimmunoassay for clonidine has been developed. Synthesis and analysis of the hapten (4-carboxy-clonidine; St 1984) as well as antibody production in rabbits are described in detail. At a final dilution of 1:1000 the resulting immune serum binds 50% of a tritiated clonidine standard containing 1 ng of clonidine. The detection limit of the presented radioimmunoassay for clonidine is 0.1 ng/ml. The coefficient of variation did not exceed 4.3% for any of 7 standard determinations with 5 replicates. There was no relevant cross-reactivity of inactive clonidine metabolites apart from 4-OH-clonidine. To avoid any errors from cross-reaction clonidine was selectively and quantitatively extracted into diethylether from unknown plasma samples. Following concentration of the extracts even such low concentrations as 20 pg of clonidine/ml plasma were detectable. With the radioimmunoassay applied in pharmacokinetic studies a maximal clonidine concentration in blood plasma of healthy human volunteers was determined to 0.6 ng/ml 1.5 h after oral administration of 150 micrograms.

The on column methylation of clonidine and p-hydroxyclonidine with trimethylanilinium hydroxide.

The structures of the methylated clonidine derivatives formed by on column methylation with trimethylanilinium hydroxide are revised. The almost exclusive formation of derivatives of phenylimino-N,N-dimethylimidazolidine structure is explained in terms of a fast kinetically controlled reaction of substrate anions. The reliability of a stable isotope dilution assay for clonidine is discussed in view of these results.