Human microdose evaluation of the novel EP1 receptor antagonist GSK269984A

AIM

The primary objective was to evaluate the pharmacokinetics (PK) of the novel EP₁ antagonist GSK269984A in human volunteers after a single oral and intravenous (i.v.) microdose (100 µg).

METHOD

GSK269984A was administered to two groups of healthy human volunteers as a single oral (n= 5) or i.v. (n= 5) microdose (100 µg). Blood samples were collected for up to 24 h and the parent drug concentrations were measured in separated plasma using a validated high pressure liquid chromatography-tandem mass spectrometry method following solid phase extraction.

RESULTS

Following the i.v. microdose, the geometric mean values for clearance (CL), steady-state volume of distribution (V_ss) and terminal elimination half-life (t_1/2) of GSK269984A were 9.8 l h⁻¹, 62.8 l and 8.2 h. C_max and AUC(0,∞) were 3.2 ng ml⁻¹ and 10.2 ng ml⁻¹ h, respectively; the corresponding oral parameters were 1.8 ng ml⁻¹ and 9.8 ng ml⁻¹ h, respectively. Absolute oral bioavailability was estimated to be 95%. These data were inconsistent with predictions of human PK based on allometric scaling of in vivo PK data from three pre-clinical species (rat, dog and monkey).

CONCLUSION

For drug development programmes characterized by inconsistencies between pre-clinical in vitro metabolic and in vivo PK data, and where uncertainty exists with respect to allometric predictions of the human PK profile, these data support the early application of a human microdose study to facilitate the selection of compounds for further clinical development.     

A pharmacokinetic and pharmacodynamic interaction study between nebivolol and the H2-receptor antagonists cimetidine and ranitidine

Aims The study was designed to investigate the effects of the H₂-receptor antagonists, cimetidine and ranitidine on the pharmacokinetics and pharmacodynamics of nebivolol in healthy volunteers. Methods Twelve healthy volunteers took part in a randomized placebo-controlled cross-over study. Each subject received on three separate occasions placebo, cimetidine (400 mg twice daily) or ranitidine (150 mg twice daily) for 24 h before and 48 h after a single oral dose of nebivolol (5 mg). Nebivolol and its individual (+) and (−) enantiomers were determined tby h.p.l.c. Results Ranitidine had no significant effect on nebivolol pharmacokinetics. Cimetidine, however, resulted in a 21–23% increase in C_max of unchanged nebivolol and of each enantiomer plus its hydroxylated metabolites. Cimetidine significantly (P<0.05) increased the AUC [mean±s.d. (95% C.I. of differences in mean)] for unchanged (±)-nebivolol [7.76±3.07 ng ml⁻¹h with placebo; 11.50±5.40 (1.75, 8.76) ng ml⁻¹h with cimetidine], (+)-nebivolol plus its hydroxylated metabolites [73.0±18.0 ng ml⁻¹h with placebo; 91.5±25.7 (1.0, 23.1) ng ml⁻¹h with cimetidine] and (−)-nebivolol plus its hydroxylated metabolites [101±32 ng ml⁻¹h with placebo; 123±38 (3.3, 27.0) ng ml⁻¹h with cimetidine]. Statistical analysis of the resting blood pressure and heart rate and exercise data did not suggest any consistent effects of ranitidine or cimetidine upon the pharmacodynamic effects of nebivolol. Conclusions There was no interaction between ranitidine and nebivolol. Although cimetidine inhibited nebivolol metabolism, it did not have a significant influence on the pharmacodynamics of the drug.     

Histamine response and local cooling in the human skin: involvement of H1- and H2-receptors

AIMS: Histamine may contribute locally to cutaneous blood flow control under normal and pathologic conditions. The objective of this study was to observe the influence of skin temperature on histamine vasodilation, and the roles of H1-and H2-receptors using novel noninvasive methods. METHODS: Eleven healthy subjects received, double-blind, single doses of the H1-receptor antagonist cetirizine (10 mg), cetirizine (10 mg) plus the H2-receptor antagonist cimetidine (400 mg), or placebo on separate occasions. Histamine was dosed cumulatively by iontophoresis to the forearm skin at 34 degrees C and 14 degrees C. Laser-Doppler flux (LDF) was measured at the same sites using customised probeholder/iontophoretic chambers with Peltier cooling elements. Finger mean arterial pressure (MAP) was measured and cutaneous vascular conductance calculated as LDF/MAP. RESULTS: Histamine vasodilation was reduced in cold skin. Cetirizine shifted the histamine dose-response at both temperatures: statistically significantly at 14 degrees C only. Combined H1- and H2-receptor antagonism shifted the response significantly at both temperatures. CONCLUSIONS: H1- and H2-receptors mediate histamine-induced skin vasodilation. The sensitivity of these receptors, particularly the H1- receptor, is attenuated at low skin temperature. Whether the reduced effect in cold skin represents specific receptor or postreceptor desensitization, or nonspecific attenuation of cutaneous vasodilation remains to be elucidated.     

EFFECTS OF HISTAMINE H1 AND H2-RECEPTOR ANTAGONISTS IN THE CRANIAL CIRCULATION OF THE MONKEY

1. The effects of the histamine H₂-receptor antagonists, metiamide and cimetidine, and the Hi-receptor antagonist, mepyramine, on cranial vasodilator and systemic vasodepressor responses to histamine have been investigated in anaesthetized monkeys. 2. In monkeys treated with successively increasing intravenous doses of 0.25, 1 and 5 mg/kg of metiamide, histamine-induced decreases in external and internal carotid vascular resistances were blocked, but systemic vasodepressor responses were not affected. 3. In monkeys treated similarly with 0.25, 1 and 5 mg/kg of cimetidine, external carotid vascular responses to histamine were blocked, but internal carotid vascular and systemic vasodepressor responses to histamine were not affected. 4. In monkeys treated similarly with 0.5, 2 and 10 mg/kg of mepyramine, histamine-induced systemic vasodepressor responses were blocked, but responses in the external and internal carotid circulations were unaffected. 5. In those monkeys treated with mepyramine after initial H₂-receptor antagonist treatment, blockade of internal, but not external, carotid vascular responses to histamine appeared to be increased. 6. The histamine antagonists did not affect cranial vascular responses to noradrenaline, serotonin, prostaglandin E₁ or bradykinin. Metiamide and cimetidine had no appreciable direct effects, but mepyramine produced short-lasting changes (vasodilatation followed by vasoconstriction). 7. These results indicate that H₂-receptors are involved in the external and internal carotid vascular effects of histamine. Hi-Receptors do not appear to contribute to the external carotid vasodilator response to histamine, but their possible involvement in the internal carotid response cannot be excluded.     

Histamine H2-receptor antagonists have no clinically significant effect on the steady-state pharmacokinetics of voriconazole

Aims  Voriconazole, a new triazole antifungal agent, is metabolized mainly by cytochrome P450s CYP2C19 and CYP2C9, and also by CYP3A4. The aim of this open-label, placebo-controlled, randomized, three-way crossover study was to determine the effects of cimetidine and ranitidine on the steady-state pharmacokinetics of voriconazole.
Methods  Twelve healthy male subjects received oral voriconazole 200 mg twice daily plus cimetidine 400 mg twice daily, voriconazole 200 mg twice daily plus ranitidine 150 mg twice daily, and voriconazole 200 mg twice daily plus placebo twice daily. Treatment periods were separated by at least 7 days.
Results  When cimetidine was administered with voriconazole, the maximum plasma voriconazole concentration ( C _max) and the area under the plasma concentration–time curve of voriconazole (AUC_τ) was increased by 18.3%[90% confidence interval (CI) 6.0, 32.0] and 22.5% (90% CI 13.3, 32.5), respectively. Concomitant ranitidine had no significant effect on voriconazole C _max or AUC_τ. Time of C _max ( t _max) elimination half-life ( t _1/2) or terminal phase rate constant ( k _el) for voriconazole were similar in all three treatment groups. Most adverse events were mild and transitory; two subjects were withdrawn due to adverse events.
Conclusions  Coadministration of the histamine H₂-receptor antagonists cimetidine or ranitidine does not affect the steady-state pharmacokinetics of voriconazole in a clinically relevant manner.     

The clinical pharmacokinetics of buflomedil in normal subjects after intravenous and oral administration

Summary A dose-ranging pharmacokinetic study of buflomedil was carried out in eight subjects to determine the pharmacokinetic parameters of the drug after oral and intravenous administration. Based on AUC analyses, the pharmacokinetics of buflomedil were found to be linear within the dose ranges studied (50 to 200 mg for i. v. injection and 150 to 450 mg for oral administration). In the oral study, the mean biological half-life of the drug was 2.97 h, while after intravenous dose it was 3.25 h. The apparent volume of distribution after the pseudodistribution equilibrium (F_d) and volume of distribution at the steady state (V_dss) were 1.43±0.24 l/kg and 1.32±0.26 l/kg, respectively. The mean urinary recovery of intact drug and the metabolite, paradesmethyl buflomedil, after intravenous dosing, were 23.6% and 18.7%, respectively, while after oral dosing, they were 18% and 14.8%, respectively. On the average, 72% of the dose was obserbed into the systemic circulation after oral administration. This level of bioavailability was attributed to the hepatic first-pass effect.     

Four phase 1 trials to evaluate the safety and pharmacokinetic profile of single and repeated dosing of SCO‐101 in adult male and female volunteers

SCO‐101 (Endovion) was discontinued 20 years ago as a new drug under development against sickle cell anaemia. Data from the phase 1 studies remained unpublished. New data indicate that SCO‐101 might be efficacious as add‐on therapy in cancer. Thus, we report the results from the four phase 1 trials performed between 2001 and 2002. Adult volunteers received SCO‐101 or placebo in four independent trials. Adverse events were recorded, and SCO‐101 was determined for pharmacokinetic analysis. Ninety‐two volunteers completed the trials. The most remarkable adverse effect was a transient and dose‐dependent increase in unconjugated bilirubin. Plasma SCO‐101 elimination was approximately log linear, with apparent oral clearances of between 315 and 2103 mL/h for single doses, and between 121 and 2433 mL/h at steady state following oral administration. There was a marked decrease in clearance with increasing dose, and for repeated dose versus single dose. T_max was greater, and C_max and AUC_∞ were lower in the fed state compared to the fasted state. Exposure was equivalent in males and females and for African Americans and Caucasians. In conclusion, SCO‐101 appears to be a safe drug with a predictable PK profile. Its efficacy as add‐on to standard anticancer drugs has yet to be defined.     

Pharmacokinetics and tolerance of intravenous and intramuscular phylloquinone(vitamin K1) mixed micelles formulation

1 The pharmacokinetics and tolerance of phylloquinone(vitamin K₁) mixed micelles formulation (Konakion^® MM) were evaluated, in normal human adult volunteers ( n =30) using an open randomized crossover design protocol following a 10  mg intravenous or intramuscular injection.
2 Blood samples were collected for up to 12  h after the intravenous and up to 72  h after the intramuscular injections and the phylloquinone(vitamin K₁) levels determined by reversed phase h.p.l.c. with fluorometric detection after post-column electrochemical reduction.
3 Konakion^® MM was well tolerated after either route of administration. Pharmacokinetic analysis of plasma phylloquinone(vitamin K₁) concentration vs time profiles revealed that in one-fifth of the subjects systemic availability of intramuscular phylloquinone(vitamin K₁) was below 65%.
4 Our data suggest that due to sustained, but irregular and unpredictable absorption of the phylloquinone(vitamin K₁) from the depot site, the intramuscular route of Konakion^® MM administration is not suitable and thus not recommended.
5 Konakion^® MM i.v. is indicated to be well tolerated and effective in antagonizing coumarin-type-anticoagulants like Marcoumar^®     

Determination of pharmacokinetic parameters of vitamin K1 in rats after an intravenous infusion

Pharmacokinetic parameters of vitamin K1 have a large range of values in different literature. The aim of this study was to determine the pharmacokinetic parameters of vitamin K1 following post-constant speed intravenous infusion (PCSII) to provide rational pharmacokinetic parameters of vitamin K1 and compare these with results of noncompartmental analysis following intravenous injection (IV). After 15 hours intravenous infusion of vitamin K1 in rats, the logarithmic concentration–time curve of vitamin K1 was fit to a linear equation following PCSII (R² = 0.9599 ± 0.0096). Then, half-time (T_1/2), apparent volume of distribution (V_d), and clearance rate (CL) were estimated successively. T_1/2 of vitamin K1 was 4.07 ± 0.41 hour, CL was 89.47 ± 3.60 mL/h, and V_d was 525.38 ± 54.45 mL in rats following PCSII. There was no significant difference in pharmacokinetic parameters of vitamin K1 among different sampling times. For noncompartmental analysis, T_1/2 and mean residence time (MRT_INF) for a sampling duration of 6h were shorter than those of 12 hours or 24 hours sampling duration following IV (P < .05, P < .01). In addition, T_1/2 of vitamin K1 was obviously different from MRT-equated half-time (T_{1/2, MRT})(P < .05). V_d and CL of vitamin K1 following PCSII were larger than those following IV based on noncompartmental analysis (P < .01). The results demonstrated that drug distribution in the body was balanced and the Napierian logarithmic concentration–time curve of vitamin K1 fit to a linear equation following PCSII. Vitamin K1 has a long T_1/2 and a relatively large V_d following PCSII.     

A phase I clinical and pharmacokinetic study of the oral and the oral/ intravenous administration of menogaril

Summary Thirty-five patients with advanced refractory cancer were enrolled on this phase I study of menogaril administered orally every 4 weeks at dosages ranging from 85 mg/m² to 625 mg/m². An additional 12 patients received alternating oral and IV doses of menogaril (250 mg/m² IV; 250–500 mg/m² oral) with accompanying blood and urine sampling for pharmacokinetics analysis. Nausea and vomiting were the dose-limiting toxicities at the 625 mg/m² dosage level; vomiting was inadequately relieved by prophylactic antiemetics at this dosage level. Other toxicities included sporadic leukopenia at all dosage levels; at dosages of 500 mg/m² and 625 mg/m², leukopenia < 3000/l occurred in 7 of 24 patients. Anemia and thrombocytopenia were much less frequent toxicities. Among the patients receiving IV menogaril, peripheral vein phlebitis, leukopenia and anemia were the predominant toxicities. No antitumor responses were observed, yet one patient with nonsmall cell lung cancer experienced a 30% reduction in metastatic tumor nodules.For the patients receiving alternating oral and IV menogaril, comparative pharmacokinetic analyses were performed by HPLC. After oral administration, maximum plasma concentrations were achieved in an average of 6 hours; maximum plasma concentrations were less than one-quarter of those achieved after intravenous administration. The harmonic mean (±SD) terminal disposition half-life after oral dosing was 29.3 ±9.2 hours; mean systemic bioavailability was 33.6±10.5% after oral dosing. Forty-eight hours after an oral dose, mean cumulative urinary excretions of menogaril and the primary metabolite, N-demethylmenogaril, were 4.00±0.96% and 0.44±0.16%, respectively.Because of the poor tolerance of oral menogaril and minimal evidence of biological activity, this schedule of drug administration is not recommended for phase II evaluation. Based on this and other published studies of oral menogaril, frequent chronic low-intermediate dosages of the drug may be given orally with potentially better tolerance and antitumor activity.     

三七皂苷中人参皂苷Rg1与Rb1口服吸收及其体内药代动力学的研究和比较

分别考察三七总皂苷(PNS)在大鼠灌胃和静脉给药后的人参皂苷Rg₁(Rg₁)、人参皂苷Rb₁(Rb₁)的胆汁排泄；采用平衡透析法测定药物的血浆蛋白结合率；并结合药代动力学的实验结果，研究和比较Rg₁与Rb₁的口服吸收及其体内药代动力学性质。结果表明，静脉给药后10 h，Rg₁及Rb₁胆汁排泄累积量分别为给药剂量的(61.48±18.30)%和(3.94±1.49)%；灌胃给药后12 h，Rg₁及Rb₁胆汁排泄累积量分别为给药剂量的(0.91±0.51)%和(0.055±0.02)%。Rg₁及Rb₁的血浆蛋白结合率分别为6.56%～12.74%和80.11%～89.69%。Rg₁的胃、肠和肝的通过率(F_S，F_I和F_H)分别为49.85%，13.05%和50.56%；Rb₁分别为25.82%，4.18%和65.77%。因此，肠壁吸收差是Rg₁和Rb₁生物利用度低的主要原因。Rg₁具有较高的胆汁排泄和较低的血浆蛋白结合率，Rb₁的胆汁排泄较低，而血浆蛋白结合率较高。Rb₁的肠黏膜透过性和体内消除速度都低于Rg₁，但前者的平均滞留时间(MRT)和血药浓度曲线下面积(AUC)均大于后者。     

Pharmacological characterization of cardiac histamine receptors: Sensitivity to H1- and H2-receptor agonists and antagonists

In the isolated guinea pig heart, histamine H₁-receptor antagonists inhibit the histamine-induced negative dromotropic effect, but not the positive inotropic and chronotropic effects (Levi and Kuye, 1974, European J. Pharmacol. 27, 330). Burimamide, the H₂-receptor antagonist, inhibits the positive chronotropic effect of histamine (Black et al., 1972, Nature 236, 385). In this study, the hypothesis that H₁- and H₂-receptors selectively mediate the various cardiac effects of histamine was tested: (a) by investigating the inhibition of cardiac histamine effects by burimamide; (b) by studying the cardiac effects of 2-methylhistamine (an H₁-agonist) and 4-methylhistamine (an H₂-agonist). Burimamide, as a function of concentration, inhibited the positive inotropic and chronotropic effects of histamine, whereas it attenuated the negative dromotropic effect of histamine at the higher concentration only. 4-Methylhistamine caused dose-dependent positive inotropic and chronotropic but not negative dromotropic effects; conversely, with 2-methylhistamine the negative dromotropic effect prevailed. Sinus tachycardia and slowing of atrioventricular conduction were also obtained in the guinea pig in vivo by the i.v. administration of histamine. Burimamide selectively antagonized the positive chronotropic effect, whereas promethazine (an H₁-antagonist) selectively inhibited the negative dromotropic effect. These results substantiate the hypothesis that H₂-receptors mediate the histamine-induced increase in rate and contractility, whereas H₁-receptors mediate the slowing of atrioventricular conduction.     

Study of cardiac repolarization in healthy volunteers performed with mizolastine, a new H1-receptor antagonist

AIMS: The occurrence of serious dysrhythmias, such as torsades de pointes, with terfenadine and astemizole had led to a reexamination of the potential effect of H1 antihistamines on cardiac repolarization. Mizolastine is a potent, selective, nonsedating peripherally acting H1-receptor antagonist which is registered for rhinitis and urticaria at a recommended dose of 10 mg once daily. The present study was carried out to investigate the effects of therapeutic and supratherapeutic doses of mizolastine, on ventricular repolarization in healthy volunteers. METHODS: Twenty-four healthy young volunteers participated in a double-blind, placebo-controlled, randomised study with three parallel groups. Each group consisted of 2 way cross-over 7 day treatment periods where mizolastine (10, 20 or 40 mg) and placebo were randomly administered. On day 1 and day 7, 12-lead ECG recordings were performed prior and 0.5, 1, 2, 3, 4, 6, 8, 12, 16, and 20 h after dosing and from day 2 to day 6, before dosing and 1, 2, 3, and 4 h after. RESULTS: Whatever the analysis used (raw data, changes from baseline, incidence of individual out-of-range values) no significant differences were observed at any dose level vs placebo, on any of ECG parameters (HR, PR, QRS, QT, and QTc). In particular, no effect of mizolastine vs placebo was shown on QT and QTc although 95% CIs were wide. The only subject who exhibited a QTc>/=450 ms received placebo for 7 days. CONCLUSIONS: This study found no evidence of an effect of mizolastine up to 40 mg (four times the therapeutic dose) on ventricular repolarization in healthy volunteers.     

Stereoselective pharmacokinetic analysis of tramadol and its main phase I metabolites in healthy subjects after intravenous and oral administration of racemic tramadol

The kinetics of tramadol enantiomers are stereoselective when doses of the racemic drug are given orally. To document whether the route of administration determines the stereoselective kinetics of tramadol enantiomers, healthy volunteers received 100 mg oral or intravenous doses of racemic tramadol, and serial blood samples were obtained to assay tramadol enantiomers and their main phase I metabolites, O-demethyltramadol and N-demethyltramadol. To assess accurately the involvement of their metabolites in the pharmacokinetics of tramadol, it is essential to determine the rate and extent of the formation of the enantiomers of these metabolites. A simultaneous pharmacokinetic model describing the plasma concentration-curves of the generated metabolites and the parent compounds after intravenous and oral drug administration is developed and presented. Tramadol and O-demethyltramadol were the major compounds detected in plasma after intravenous administration. Nevertheless, the N-demethylation of tramadol showed a significant increase when the oral route was used. After both oral and intravenous doses, the kinetics of the tramadol enantiomers were stereoselective. The AUC for (R )-(+)-tramadol was greater than the AUC for (S)-(-)-tramadol. The formation of N-demethyltramadol also was enantioselective after oral administration of racemic tramadol, with a greater AUC for (R)-(+)-N-demethyltramadol than for (S)-(-)-N-demethyltramadol. In the opposite form, (S)-(-)-O-demethyltramadol was formed faster than (R)-(+)-O-demethyltramadol. The metabolism of tramadol was also route-dependent with a different enantiomeric ratio for tramadol and its main phase I metabolites after intravenous and oral administration. The disposition of N-demethyltramadol was concentration-dependent.     

Pharmacokinetics of α-dihydroergocriptine in rats after single intravenous and single and repeated oral administrations

The pharmacokinetics of α-dihydroergocriptine methane sulphonate in rats were investigated using an HPLC method for the detection of unchanged α-dihydroergocriptine (DHEK) in plasma, organs (kidneys, heart, lungs, spleen, liver, and brain), and urine. The plasma profile of DHEK obtained after intravenous administration at a dose of 5 mg kg^?1 (as base) of DHEK methane sulphonate showed a three compartment pharmacokinetic model with an elimination half-life of 6.78 h. The kinetics of DHEK after a single oral administration at a dose of 20 mg kg^?1 (as base) showed two peaks: the second peak, at about 6 h, was probably due to an enterohepatic cycle. The disposition of DHEK consisted of an absorption half-life of 0.02 h, a distribution half-life of 2.15 h and an elimination half-life of 5.83 h. The pharmacokinetics of DHEK, after repeated oral administrations at the same dose, were similar to those after a single oral administration. The absolute bioavailability was 4.14% after a single oral administration and 3.95% after repeated oral administrations. The analysis of the organs showed that DHEK was rapidly absorbed and distributed in all tissues, mostly in lungs, kidneys, and liver, but it is interesting to observe that it also reached the brain. After repeated oral administrations plasma and tissue concentrations were similar to those obtained after a single administration; therefore it is possible to exclude the onset of autoinduction or accumulation phenomena of DHEK in rats' organs. Urinary excretion of the unchanged drug was low (0.38% of the administered dose in the intravenous route and 0.04% in the oral route), being in agreement with a low oral bioavailability and a rapid and extensive metabolism (first-pass effect).     

Pharmacokinetics of xamoterol after intravenous and oral administration to volunteers

Summary The pharmacokinetics of xamoterol, a -adrenoceptor partial agonist under clinical evaluation for the treatment of mild to moderate heart failure, have been studied in 12 healthy male subjects. They received 14 mg i.v. and oral doses of 50 and 200 mg as a tablet and 200 mg as a solution in a 4 way cross-over design.After i.v. dosing the elimination half-life was 7.7 h, the total body clearance was 224 ml·min^–1 and the volume of distribution at steady-state (V_ss) was 48 l. Sixty-two percent of the dose was recovered unchanged in urine. After oral doses, the absolute bioavailability of xamoterol was shown to be 5% irrespective of whether the dose was administered as a tablet or solution. Peak plasma concentrations occurred at about 2 h for the tablet dose and slightly earlier (1.4 h) for the solution. Peak plasma concentration, AUC and urinary recovery of unchanged drug increased in proportion to dose. The apparent elimination half-life after oral doses (16 h) was significantly longer than that observed after an intravenous dose.Despite the low bioavailability, the degree of inter-subject variability of oral bioavailability was small probably indicating that the controlling factor is the hydrophilic nature of the molecule rather than extensive first pass metabolism or poor dissolution of xamoterol from the tablet formulation.     

Metabolism and pharmacokinetics of prostaglandin E1 administered by intravenous infusion in human subjects

In a single-blind, randomized, two-way crossover study with 12 healthy male volunteers, 60 g of prostaglandin E₁ (PGE₁) or placebo was administered by intravenous infusion during a 120-min period. PGE₁, 13,14-dihydro-PGE₁ (PGE₀) and 15-keto-PGE₀ plasma concentrations were measured by a highly specific and sensitive GC-MS/MS method.Endogenous PGE₁ plasma concentrations ranged between 1.2 and 1.8 pg·ml^–1. Endogenous PGE₀ and 15-keto-PGE₀ plasma concentrations varied from 0.8 to 1.3 pg·ml^–1 and from 4.2 to 6.0 pg/ml respectively. During intravenous infusion of PGE₁, plasma PGE₁ concentrations rose to a level twice as high as during the placebo infusion. In contrast, PGE₀ plasma concentrations were 8 times higher during PGE₁ infusion than during placebo infusion, and 15-keto-PGE₀ plasma concentrations were 20 times higher.The new analytical method has thus been useful to describe the pharmacokinetics of PGE₁ and its metabolites PGE₀ and 15-keto-PGE₀, during and after intravenous infusion of PGE₁.     

Pharmacokinetics of benzydamine after intravenous, oral, and topical doses to human subjects

The pharmacokinetics of the anti-inflammatory drug benzydamine were determined after intravenous infusion of 5 mg to six healthy male subjects. Benzydamine was characterized as a drug of relatively low systemic clearance (ca. 160 ml min-1) but high volume of distribution (ca. 1101); the apparent terminal half-life in plasma was ca. 8 h. Benzydamine was well absorbed after oral administration, as indicated by a mean systemic availability of 87 per cent. However, absorption of the drug was low (less than 10 per cent of the dose) after its use by male subjects as a mouthwash, or after its application to female subjects as dermal cream and vaginal douche preparations. The data suggest that benzydamine is generally not well absorbed through the skin and non-specialized mucosae, thereby limiting unrequired systemic exposure to this drug when it is used by these routes.     

A human capecitabine excretion balance and pharmacokinetic study after administration of a single oral dose of 14C-labelled drug

An excretion balance and pharmacokinetic study was conducted in cancer patients with solid tumors who received a single oral dose of capecitabine of 2000 mg including 50 Ci of ¹⁴C-radiolabelled capecitabine. Blood, urine and fecal samples were collected until radioactive counts had fallen to below 50 dpm/mL in urine, and levels of intact drug and its metabolites were measured in plasma and urine by LC/MS-MS (mass spectrometry) and ¹⁹F-NMR (nuclear magnetic resonance) respectively. Based on the results of the 6 eligible patients enrolled, the dose was almost completely recovered in the urine (mean 95.5%, range 86–104% based on radioactivity measurements) over a period of 7 days after drug administration. Of this, 84% (range 71–95) was recovered in the first 12 hours. Over this time period, 2.64% (0.69–7.0) was collected in the feces. Over a collection period of 24–48h, a total of 84.2% (range 80–95) was recovered in the urine as the sum of the parent drug and measured metabolites (5-DFCR, 5-DFUR, 5-FU, FUH₂, FUPA, FBAL). Based on the radioactivity measurements of drug-related material, absorption is rapid (t_max 0.25–1.5 hours) followed by a rapid biphasic decline. The parent drug is rapidly converted to 5-FU, which is present in low levels due to the rapid metabolism to FBAL, which has the longest half-life. There is a good correlation between the levels of radioactivity in the plasma and the levels of intact drug and the metabolites, suggesting that these represent the most abundant metabolites of capecitabine. The absorption of capecitabine is rapid and almost complete. The excretion of the intact drug and its metabolites is rapid and almost exclusively in the urine.     

猕猴硬膜外及静脉注射 [~(125)I]虎纹毒素-1的药代动力学(英文)

目的　研究与比较猕猴硬膜外 (ed)及静脉 (iv)注射虎纹毒素 1后的药代动力学过程。方法　Iodogen法标记虎纹毒素 1 ,按 0 388MBq·kg- 1 的剂量向猕猴第 3和第 4腰椎之间硬膜外腔及静脉注射标记后虎纹毒素 1 ,用反相高效液相色谱检测猴血清中的药物放射性活度 ;γ 计数仪检测猴第 3和第 4腰椎硬膜外腔的药物放射性活度。结果　制备了具有生物活性的 [1 2 5I]虎纹毒素 1。硬膜外给药 1 0min后 ,给药部位局部硬膜外腔的药物放射性占总给药量的0 38,说明硬膜外给药是成功的 .硬膜外及静脉给药后 ,血药浓度分别在 30min和 2min达峰 ,分别为 (0 70± 0 0 4 )MBq·L- 1 和 (4 98± 0 58)MBq·L- 1 。两种给药途径的药时曲线不同 :猕猴硬膜外和静脉给药后 ,末端T12 分别为(1 0 36± 0 2 7)h和 (1 1 0 3± 1 1 6)h ;ClS 分别为 (1 2 9±0 0 7)L·h- 1 ·kg- 1 和 (1 2 5± 0 2 3)L·h- 1 ·kg- 1 ,硬膜外给予 [1 2 5I]HWTX 1的绝对生物利用度 (95± 5) %。结论　硬膜外和静脉两种给药方式下 ,[1 2 5I]虎纹毒素 1在猕猴体内的药代动力学过程具有差异性 ,两种给药方式下 [1 2 5I]在猕猴体内的分布与吸收特点对于虎纹毒素 I的临床药效学和毒理学研究提供了参考数据。