Effects of Intravenous Dexmedetomidine in Humans

Dexmedetomidine (DMED) is a novel clonidine-like compound known to have sedative, analgesic, and cardiovascular stabilizing qualities. DMED is a more highly selective alpha 2-adrenergic agonist than clonidine. This investigation examined the hemodynamic effects of four selected iv doses in consenting healthy male volunteers. In a randomized, double-blind, placebo-controlled trial subjects received 0 (n = 9), 0.25 (n = 6) 0.5 (n = 6), 1.0 (n = 6), or 2.0 (n = 10) micrograms/kg of DMED by infusion (2 min). ECG, heart rate (HR), arterial blood pressure (MABP), bioimpedance cardiac output (CO), and plasma catecholamines concentrations (CA) were monitored from 90 min before to 360 min after infusion. Plasma DMED concentrations were measured. DMED produced a maximum decrease in MABP at 60 min of 14%, 16%, 23%, and 27% for the 0.25, 0.5, 1.0, and 2.0 micrograms/kg groups, respectively (P < .05). At 330 min MABP remained below baseline by 8% and 17% at the two largest doses (P < .05). Both HR and CO decreased maximally by both 17% at 105 min. The two largest doses produced a transient (peak at 3 min lasting < 11 min) increased in MABP (16 +/- 2.5 and 24 +/- 10 mmHg, respectively; P < .05) with a concomitantly reduced CO (41%, 2 micrograms/kg; P < .05) and HR (22%, 2 micrograms/kg; P < .05), whereas systemic vascular resistance doubled. Even the lowest dose decreased CA immediately to values close to 20 pg/ml for 5 h. A 2-min iv infusion of DMED produced a transient increase in MABP and a longer lasting decrease in MABP and CA. These DMED doses were well tolerated in the healthy volunteers.

The Euro-Balance Trial: The effect of a new biocompatible peritoneal dialysis fluid (balance) on the peritoneal membrane

BACKGROUND

Although peritoneal dialysis (PD) is a widely accepted form of renal replacement therapy (RRT), concerns remain regarding the bioincompatible nature of standard PD fluid. In order to evaluate whether a newly formulated fluid of neutral pH, and containing low levels of glucose degradation products (GDP), resulted in improved in vivo biocompatibility, it was compared in a clinical study to a standard PD fluid.

METHODS

In a multicenter, open, randomized, prospective study with a crossover design and parallel arms, a conventional, acidic, lactate-buffered fluid (SPDF) was compared with a pH neutral, lactate-buffered, low GDP fluid (balance). Overnight effluent was collected and assayed for cancer antigen 125 (CA125), hyaluronic acid (HA), procollagen peptide (PICP), vascular endothelial growth factor (VEGF), and tumor necrosis factor alpha (TNFalpha). Serum samples were assayed for circulating advanced glycosylation end products (AGE), N(epsilon)-(carboxymethyl)lysine (CML), and imidazolone. Clinical end points were residual renal function (RRF), adequacy of dialysis, ultrafiltration, and peritoneal membrane function. Eighty-six patients were randomized to either group I starting with SPDF for 12 weeks (Phase I), then switching to "balance" for 12 weeks (Phase II), or group II, which was treated vice versa. Seventy-one patients completed the study with data suitable for entry into the per protocol analysis. Effluent and serum samples, together with peritoneal function tests and adequacy measurements, were undertaken at study centers on three occasions during the study: after the four-week run-in period, after Phase I, and again after Phase II.

RESULTS

In patients treated with balance there were significantly higher effluent levels of CA125 and PICP in both arms of the study. Conversely, levels of HA were lower in patients exposed to balance, while there was no change in the levels of either VEGF or TNFalpha. Serum CML and imidazolone levels fell significantly in balance-treated patients. Renal urea and creatinine clearances were higher in both treatment arms after patients were exposed to balance. Urine volume was higher in patients exposed to balance. In contrast, peritoneal ultrafiltration was higher in patients on SPDF. When anuric patients were analyzed as a subgroup, there was no significant difference in peritoneal transport characteristics or in ultrafiltration on either fluid. There were no changes in peritonitis incidence on either solution.

CONCLUSION

This study indicates that the use of balance, a neutral pH, low GDP fluid, is accompanied by a significant improvement in effluent markers of peritoneal membrane integrity and significantly decreased circulating AGE levels. Clinical parameters suggest an improvement in residual renal function on balance, with an accompanying decrease in peritoneal ultrafiltration. It would appear that balance solution results in an improvement in local peritoneal homeostasis, as well as having a positive impact on systemic parameters, including circulating AGE and residual renal function.

Column-switching HPLC for the analysis of plasma in PET imaging studies

A column-switch high performance liquid chromatography method for the analysis of 4 mL of plasma is described with six examples of chromatography of [(11)C]-labeled positron-emission tomography imaging agents. Complete extraction of all but the most polar metabolites by the reverse phase capture column is achieved by disruption of plasma protein binding by 8 M urea.

Oral resiquimod in chronic HCV infection: safety and efficacy in 2 placebo-controlled, double-blind phase IIa studies

BACKGROUND/AIMS

To explore safety, pharmacokinetics, and pharmacodynamics of oral administration of resiquimod, a Toll-like receptor 7 and 8 agonist that induces endogenous interferon-alpha, in subjects with chronic hepatitis C virus infection.

METHODS

Two randomized, double-blind phase IIa studies of resiquimod administered two times per week for 4 weeks. Multicenter study (U.S.): 12 subjects received resiquimod 0.01 mg/kg and 4 received placebo. Single center study (France): 6 subjects received 0.01 mg/kg, 11 received 0.02 mg/kg and 6 received placebo.

RESULTS

Resiquimod 0.01 mg/kg was tolerated; two 0.2 mg/kg subjects discontinued treatment. More subjects reported severe grade adverse events at 0.02 mg/kg; events were consistent with systemic cytokine induction, including fever, headache, shivering, and lymphopenia. Mean maximum serum resiquimod concentrations were 3.82+/-1.47 and 7.55+/-4.17 ng/mL for 0.01 mg/kg and 0.02 mg/kg, respectively. At 0.02 mg/kg, two, three and one subjects had maximal reductions in viral levels of at least 1-, 2- and 3-logs, respectively; reductions were generally transient. Interferon-alpha levels appeared correlated with decreases in viral titer and lymphocyte counts, as well as increase in neutrophil counts.

CONCLUSIONS

Oral administration of resiquimod 0.02 mg/kg transiently reduced viral levels but was associated with adverse effects similar to interferon-alpha.

Treatment of systemic mycoses with ketoconazole: emphasis on toxicity and clinical response in 52 patients. National Institute of Allergy and Infectious Diseases collaborative antifungal study

The pharmacology, in vitro mycologic activity, toxicity, and efficacy of ketoconazole were studied in a Phase-II evaluation by the National Institutes of Health and National Institute of Allergy and Infectious Disease Mycoses Study Group. This report emphasizes the toxicity and clinical response data in 52 patients with the following systemic mycoses: blastomycosis in 16 patients; nonmeningeal coccidioidomycosis in 13; histoplasmosis in 8; nonmeningeal cryptococcosis in 7; sporotrichosis in 7; and both blastomycosis and nonmeningeal coccidioidomycosis in 1. Maximum daily doses of ketoconazole were 100 mg in 1 patient; 200 mg in 23; 400 mg in 12; and 600 mg in 16. In 52% of the patients, duration of therapy ranged from less than 1 to 6 months, whereas in 35%, duration ranged from 7 to 12 months, and in 13%, from 12 to 22 months. In 35 patients (67%), evidence of toxicity was not seen. Nausea, anorexia, or vomiting occurred in 21%. Cure or marked improvement was shown in 27 patients (52%), whereas failure of the primary course was seen in 14 (27%) and relapse after ketoconazole was discontinued in 11 (21%). Although this evaluation did not provide clear-cut clinical response data, our results indicate that ketoconazole, in the dosage regimens used, was more effective in patients with histoplasmosis and nonmeningeal cryptococcosis than in patients with blastomycosis and nonmeningeal coccidioidomycosis, and least effective in patients with sporotrichosis.

Immunohistochemical detection of imidazolone, a novel advanced glycation end product, in kidneys and aortas of diabetic patients

To investigate the role of the Maillard reaction in the pathogenesis of diabetic complications, we produced several clones of monoclonal antibodies against advanced glycation end products (AGEs) by immunizing mice with AGE-modified keyhole limpet hemocyanin, and found that one clone (AG-1) of the anti-AGE antibodies reacted specifically with imidazolones A and B, novel AGEs. Thus, the imidazolones, which are the reaction products of the guanidino group of arginine with 3-deoxyglucosone (3-DG), a reactive intermediate of the Maillard reaction, were found to be common epitopes of AGE-modified proteins produced in vitro. We determined the erythrocyte levels of imidazolone in diabetic patients using ELISA with the monoclonal anti-imidazolone antibody. The imidazolone levels in the erythrocytes of diabetic patients were found to be significantly increased as compared with those of healthy subjects. Then we studied the localization of imidazolone in the kidneys and aortas obtained from diabetic patients by immunohistochemistry using the antibody. Specific imidazolone immunoreactivity was detected in nodular lesions and expanded mesangial matrix of glomeruli, and renal arteries in an advanced stage of diabetic nephropathy, as well as in atherosclerotic lesions of aortas. This study first demonstrates the localization of imidazolone in the characteristic lesions of diabetic nephropathy and atherosclerosis. These results, taken together with a recent demonstration of increased serum 3-DG levels in diabetes, strongly suggest that imidazolone produced by 3-DG may contribute to the progression of long-term diabetic complications such as nephropathy and atherosclerosis.

Increased serum levels of the specific AGE-compound methylglyoxal-derived hydroimidazolone in patients with type 2 diabetes

A time-delayed fluorescence immunoassay was developed for the determination of serum levels of methylglyoxal (MG)-derived hydroimidazolone using a monoclonal antiserum raised against Nalpha-acetyl-Ndelta-(5-hydro-5-methyl)-4-imidazolone, Europium-labeled anti-mouse IgG antiserum as indicator, and MG modified bovine serum albumin (BSA) as standard. Serum levels of hydroimidazolone were measured in 45 patients with type 2 diabetes aged 59.4 +/- 6.1 (mean +/- SD) years and with duration of diabetes of 7.3 +/- 3.1 years, and in 19 nondiabetic controls aged 56.3 +/- 4.3 years. The serum levels of hydroimidazolone were significantly higher in patients compared to controls: median, 3.0 (5-95 percentile, 1.6 to 5.4) U/mg protein versus 1.9 (1.2 to 2.8) U/mg protein (P =.0005). Significant positive correlations were observed between the serum levels of hydroimidazolone and serum levels of advanced glycation end products (AGEs), measured with a polyclonal anti-AGE antibody: r = 0.59 for patients (P <.0001), and r = 0.65 for controls (P =.002). Similarly, significant correlations were also found between serum levels of hydroimidazolone and N(epsilon)-(carboxymethyl)-lysine (CML): r = 0.36 in patients and r = 0.55 for controls (both P =.02). Serum hydroimidazolone levels did not correlate with fasting plasma glucose or hemoglobin A(1c) (HbA(1c)) levels. The observed differences between patients with diabetes and nondiabetic controls seem to be comparable to differences measured for other AGE compounds.

Angiotensin II receptor-independent antiinflammatory and antiaggregatory properties of losartan: role of the active metabolite EXP3179

Angiotensin II (Ang II) type 1 receptor (AT(1)) antagonists such as losartan (LOS) are widely used for the treatment of hypertension and elicit antiinflammatory and antiaggregatory in vitro and in patients, although the underlying mechanism are unclear. Following computer-based molecule similarity, we proposed that on cytochrome-P450 degradation, the LOS metabolite EXP3179 is generated, which shows molecule homology to indomethacin, a cyclooxygenase inhibitor with antiinflammatory and antiaggregatory properties. Subsequently, serum-levels of EXP3179 were determined for 8 hours in patients receiving a single oral dose of 100 mg LOS. High-performance liquid chromatography followed by liquid chromatography-mass spectrometry (GC-MS) [corrected] from serum samples revealed a maximum of 10(-7) mol/L for EXP3179 peaking between 3 to 4 hours. The increase in serum-EXP3179 levels was associated with a significant reduction in platelet aggregation in vivo (-35+/-4%, P<0.001 versus control). EXP3179 generation was investigated in a chemical reaction mimicking the liver cytochrome-P450-dependent LOS-degradation and human endothelial cells were exposed to Ang II or lipopolysaccharides (LPS) in the presence of EXP3179 (10(-7) mol/L). LPS- and Ang II-induced COX-2 transcription was abolished by EXP3179. Moreover, EXP3179 significantly reduced Ang II- and LPS-induced formation of prostaglandin F2alpha as determined by GC-MS [corrected]. Thus, antiinflammatory properties of LOS are mediated via its EXP3179 metabolite by abolishing COX-2 mRNA upregulation and COX-dependent TXA2 and PGF2alpha generation. Serum levels of EXP3179 are detectable in patients in concentrations that exhibit antiinflammatory and antiaggregatory properties in vitro.

The pharmacokinetics and pharmacodynamics of zoledronic acid in cancer patients with varying degrees of renal function

An open-label pharmacokinetic and pharmacodynamic study of zoledronic acid (Zometa) was performed in 19 cancer patients with bone metastases and known, varying levels of renal function. Patients were stratified according to creatinine clearance (CLcr) into different groups of normal (CLcr > 80 mL/min), mildly (CLcr = 50-80 mL/min), or moderately/severely impaired (CLcr = 10-50 mL/min) renal function. Three intravenous infusions of 4 mg zoledronic acid were administered at 1-month intervals between doses. Plasma concentrations and amounts excreted in urine were determined in all subjects, and 4 patients were administered 14C-labeled zoledronic acid to assess excretion and distribution of drug in whole blood. In general, the drug was well tolerated by the patients. Mean area under the plasma concentration versus time curve and mean concentration immediately after cessation of drug infusion were lower, and mean amounts excreted in urine over 24 hours from start of infusion were higher in normal subjects than in those with impaired renal function (36% vs. 28% of excreted dose), although the differences were not significant. Furthermore, with repeated doses, there was no evidence of drug accumulation in plasma or changes in drug exposure in any of the groups, nor was there any evidence of changes in renal function status. Serum levels of markers of bone resorption (serum C-telopeptide and N-telopeptide) were noticeably reduced after each dose of zoledronic acid across all three renal groups. It was concluded that in patients with mildly to moderately reduced renal function, dosage adjustment of zoledronic acid is likely not necessary.

Imidazolium crosslinks derived from reaction of lysine with glyoxal and methylglyoxal are increased in serum proteins of uremic patients: evidence for increased oxidative stress in uremia

Glyoxal (GO) and methylglyoxal (MGO) are reactive dicarbonyl compounds formed during autoxidation of both carbohydrates and lipids. They may react with lysine and arginine residues of proteins in Maillard or browning reactions, yielding advanced glycation or lipoxidation end products. Among these are the imidazolium crosslinks, N,N(-di(N(epsilon)-lysino))imidazolium (glyoxal-lysine dimer, GOLD) and N,N(-di(N(epsilon)-lysino))-4-methyl-imidazolium (methylglyoxal-lysine dimer, MOLD). We have detected and measured GOLD and MOLD in human serum by electrospray ionization/mass spectrometry/mass spectrometry (ESI/MS/MS), using 15N4-GOLD and 15N4-MOLD as internal standards. In this report we show that levels of GOLD and MOLD are significantly elevated (3-4-fold, P< 0.01) in sera of non-diabetic uremic patients, compared to age-matched controls, and represent a major class of non-enzymatic, Maillard reaction crosslinks in plasma proteins. These results provide strong evidence for increased non-enzymatic crosslinking of tissue proteins by GO and MGO in uremia, implicating oxidative stress and resultant advanced glycation and lipoxidation reactions in tissue damage in uremia.

High-pressure liquid chromatographic analysis of cimetidine, a histamine H2-receptor antagonist, in blood and urine

A method is described for extraction of cimetidine, a histamine H2-receptor antagonist, from whole blood and urine with subsequent analysis by high-pressure liquid chromatography (HPLC). The drug is extracted from biological fluids with 1-octanol and back-extracted into dilute acid and then into a small volume of ethanol by saturation with potassium carbonate. HPLC analysis is performed on a column of 5-micrometer silica with a mixed mobile phase consisting primarily of acetonitrile. The method measures concentrations of cimetidine as low as 0.05 microgram/ml and is reproducible. Blood levels and urinary excretion data obtained with the analytical procedure are given for a group of human subjects who received 200-mg oral doses of cimetidine.

Pharmacokinetics and biochemical efficacy after single and multiple oral administration of losartan, an orally active nonpeptide angiotensin II receptor antagonist, in humans

1. The pharmacokinetics and biochemical efficacy of losartan, an orally active nonpeptide angiotensin II (AII) receptor antagonist, were evaluated in healthy male volunteers after single and multiple oral administration. 2. Plasma and urinary concentrations of losartan and its active metabolite, E-3174, were determined by a specific high performance liquid chromatographic (h.p.l.c.) method. 3. Plasma concentrations of losartan were proportional to dose over the range of 25 to 200 mg and the terminal half-lives (t1/2,z) ranged from 1.5 to 2.5 h. The mean values of Cmax and AUC0-infinity increased in a dose-dependent manner. 4. Plasma concentrations of E-3174 were higher than those of losartan at all dose levels. The values of Cmax and AUC0-infinity for E-3174 were approximately 2 and 5-8 times higher than those for losartan, respectively. Also the value of t1/2,z was 2 times longer than that of losartan. 5. After multiple dosing for 7 days, the pharmacokinetics of losartan and E-3174 each did not change significantly between day 1 and day 7. 6. Plasma renin activity (PRA) and plasma concentrations of AII increased markedly at all dose levels. Plasma aldosterone levels were slightly reduced, but a similar decrease was also observed with placebo. 7. No clinically significant adverse reaction was observed in any of the volunteers during either study. Blood counts, routine laboratory tests, urine analyses, and electrocardiograms were also not modified by losartan. 8. Losartan appears to be a potent orally active angiotensin II antagonist with a relatively long duration of action.

The effect of vardenafil, a potent and highly selective phosphodiesterase-5 inhibitor for the treatment of erectile dysfunction, on the cardiovascular response to exercise in patients with coronary artery disease

OBJECTIVES

The effect of vardenafil, a potent and highly selective phosphodiesterase-5 (PDE5) inhibitor, on symptom-limited exercise time, time to first awareness of angina, and time to ischemic threshold (ST-segment depression > or =1 mm from baseline) during exercise tolerance testing (ETT) was examined in patients with stable coronary artery disease (CAD).

BACKGROUND

Erectile dysfunction (ED) is common among men with CAD. PDE5 inhibition is increasingly the preferred treatment option for ED. However, the effect of PDE5 inhibition on exercise-induced ischemia in CAD patients has received limited prospective evaluation.

METHODS

In this double-blind, crossover, single-dose multicenter study, 41 men with reproducible stable exertional angina due to ischemic CAD received vardenafil 10 mg or placebo, followed by ETT (5 to 10 metabolic equivalents [METS], Bruce protocol) 1 h postdose. Sublingual nitrate use was prohibited for > or =24 h pre- and postexercise study days. End points included symptom-limited treadmill exercise time, time to first awareness of angina, time to ischemic threshold, and safety.

RESULTS

Relative to placebo, vardenafil 10 mg did not alter exercise treadmill time (427 +/- 105 s vs. 433 +/- 109 s, p = 0.39), or time to first awareness of angina (292 +/- 110 s vs. 291 +/- 123 s, p = 0.59), but significantly prolonged time to ischemic threshold (334 +/- 108 s vs. 381 +/- 108, p = 0.0004). At peak exercise, vardenafil 10 mg did not alter blood pressure, heart rate, or rate-pressure product relative to placebo. The most common adverse events (facial flushing and headache) were of mild or moderate intensity, and short-lived.

CONCLUSIONS

Vardenafil 10 mg did not impair the ability of patients with stable CAD to exercise at levels equivalent or greater than that attained during sexual intercourse (average of 2.5 to 3.3 METS).

Prevention of retinal vessel changes associated with diabetic retinopathy in galactose-fed dogs by aldose reductase inhibitors

Vascular changes associated with early diabetic retinopathy that include the selective degeneration of pericytes, the formation of microaneurysms and acellular capillaries, and vessel dilation have been experimentally investigated in age- and sex-matched beagle dogs fed a 30% galactose diet and treated with or without the aldose reductase inhibitors sorbinil and/or M79175. Eyes from dogs in each group were periodically enucleated during a 36-month period and their retinal capillaries were examined as trypsin-digested flat preparations. These studies reveal that the destruction of retinal pericytes to form pericyte ghosts is the earliest observable retinal vessel change occurring after 19 to 21 months of galactose feeding. By 24 months, both an irregular distribution of endothelial cell nuclei near pericyte ghosts and the presence of acellular capillaries containing neither endothelial cells nor pericytes can be observed. This was followed by the histologic appearance of microaneurysms after 27 months and the funduscopic appearance of intraretinal hemorrhages after 33 months. Varicose enlargements of capillaries were also observed in the trypsin-digested preparations from dogs fed galactose for 33 to 36 months. All of these changes are linked to the initial aldose reductase-associated destruction of pericytes. The onset and progression of these retinal changes were retarded in a dose-dependent manner with aldose reductase inhibitors.

The pharmacokinetic and metabolic profile of olmesartan medoxomil limits the risk of clinically relevant drug interaction

Orally administered olmesartan medoxomil was rapidly absorbed from the gastrointestinal tract and converted during absorption to olmesartan, the pharmacologically active metabolite that was subsequently excreted without further metabolism. The medoxomil moiety was released as diacetyl that was rapidly cleared by further metabolism and excretion. Peak plasma concentrations of olmesartan occurred 1-3 h after administration, after which concentrations decreased quickly. The elimination half-life was 10-15 h. Olmesartan medoxomil was not measurable in plasma and excreta. The volume of distribution was low, consistent with limited extravascular tissue distribution. Bioavailability (Cmax and area under the curve) increased approximately in proportion with dose, after single and multiple daily oral doses, over the therapeutic dose range (up to 40-80 mg daily), above which systemic availability of olmesartan increased less than proportionally with increase in dose. Steady-state plasma concentrations of olmesartan were reached within the first few daily oral doses. On average, approximately 40% of systemically available olmesartan was excreted by the kidneys, the remainder being excreted in faeces, following secretion in bile. Renal clearance (0.5-0.7 l/h) was independent of dose, accounting for approximately 9-12% of an oral dose. The absolute bioavailability of olmesartan from olmesartan medoxomil tablets was 28.6%. Olmesartan exhibited little or no binding to blood cells. No clinically significant steady-state pharmacokinetic interactions were observed following co-administration of olmesartan medoxomil with digoxin, warfarin and aluminium magnesium hydroxide (antacid), supporting the low potential for clinically significant pharmacokinetic interactions to occur between olmesartan medoxomil and co-administered drugs.

Computer-controlled infusion of intravenous dexmedetomidine hydrochloride in adult human volunteers

BACKGROUND

This investigation extended the pharmacokinetic analysis of our previous study, of intravenous dexmedetomidine in 10 healthy male volunteers, and prospectively tested the resulting compartmental pharmacokinetics in an additional six subjects using a computer-controlled infusion pump (CCIP) to target four different plasma concentrations of dexmedetomidine for 30 min at each concentration.

METHODS

A three-compartment mamillary pharmacokinetic model best described the intravenous dexmedetomidine concentration versus time profile following the 5 min intravenous infusion of 2 micrograms/kg in our previous study. Nonlinear regression was performed using both two-stage and pooled data techniques to determine the population pharmacokinetics. The pooled technique allowed covariates, such as weight, age, and height of the subjects, to be incorporated into the nonlinear regression to test the hypothesis that these additional covariates would reduce the residual error between the measured concentrations and the predicted values.

RESULTS

The addition of age, weight, lean body mass, and body surface area as covariates of the pharmacokinetic parameters did not improve the predictive value of the model. However, the model was improved when subject height was a covariate of the volume in the central compartment. The residual error in the pharmacokinetic model was markedly lower with the pooled versus the two-stage approach. The following pharmacokinetic values were obtained from the pooled analysis of the zero-order dexmedetomidine infusion: V1 = 8.05, V2 = 12.4, V3 = 175 (L), Cl1 = (0.0101*height [cm]) -1.33, Cl2 = 2.05, and Cl3 = 2.0 (L/min). Prospective evaluation of the pooled pharmacokinetic parameters using a computer-controlled infusion in six healthy volunteers showed the precision (average [(absolute error)/measured concentration]) of the CCIP to be 31.5% and the bias (average [error/measured concentration]) to be -22.4%. A pooled regression of the combined CCIP and zero-order data confirmed that the covariate, height (cm), was related in linear fashion to Cl1. A striking nonlinearity of dexmedetomidine pharmacokinetics related to concentration was observed during the CCIP infusion. The final pharmacokinetic values for the entire data set were: V1 = 7.99, V2 = 13.8, V3 = 187 (L), Cl1 = (0.00791*height [cm]) -0.927, Cl2 = 2.26, and Cl3 = 1.99 (L/min).

CONCLUSIONS

Pharmacokinetics of dexmedetomidine are best described by a three-compartment model. Addition of age, weight, lean body mass, and body surface area do not improve the predictive value of the model. Additional improvement in CCIP accuracy for dexmedetomidine infusions would require magnification modification of the model based on the targeted concentration.

Orteronel (TAK-700), a novel non-steroidal 17,20-lyase inhibitor: effects on steroid synthesis in human and monkey adrenal cells and serum steroid levels in cynomolgus monkeys

Surgical or pharmacologic methods to control gonadal androgen biosynthesis are effective approaches in the treatment of a variety of non-neoplastic and neoplastic diseases. For example, androgen ablation and its consequent reduction in circulating levels of testosterone is an effective therapy for advanced prostate cancers. Unfortunately, the therapeutic effectiveness of this approach is often temporary because of disease progression to the 'castration resistant' (CRPC) state, a situation for which there are limited treatment options. One mechanism thought to be responsible for the development of CRPC is extra-gonadal androgen synthesis and the resulting impact of these residual extra-gonadal androgens on prostate tumor cell proliferation. An important enzyme responsible for the synthesis of extra-gonadal androgens is CYP17A1 which possesses both 17,20-lyase and 17-hydroxylase catalytic activities with the 17,20-lyase activity being key in the androgen biosynthetic process. Orteronel (TAK-700), a novel, selective, and potent inhibitor of 17,20-lyase is under development as a drug to inhibit androgen synthesis. In this study, we quantified the inhibitory activity and specificity of orteronel for testicular and adrenal androgen production by evaluating its effects on CYP17A1 enzymatic activity, steroid production in monkey adrenal cells and human adrenal tumor cells, and serum levels of dehydroepiandrosterone (DHEA), cortisol, and testosterone after oral dosing in castrated and intact male cynomolgus monkeys. We report that orteronel potently suppresses androgen production in monkey adrenal cells but only weakly suppresses corticosterone and aldosterone production; the IC(50) value of orteronel for cortisol was ~3-fold higher than that for DHEA. After single oral dosing, serum levels of DHEA, cortisol, and testosterone were rapidly suppressed in intact cynomolgus monkeys. In castrated monkeys treated twice daily with orteronel, suppression of DHEA and testosterone persisted throughout the treatment period. In both in vivo models and in agreement with our in vitro data, suppression of serum cortisol levels following oral dosing was less than that seen for DHEA. In terms of human CYP17A1 and human adrenal tumor cells, orteronel inhibited 17,20-lyase activity 5.4 times more potently than 17-hydroxylase activity in cell-free enzyme assays and DHEA production 27 times more potently than cortisol production in human adrenal tumor cells, suggesting greater specificity of inhibition between 17,20-lyase and 17-hydroxylase activities in humans vs monkeys. In summary, orteronel potently inhibited the 17,20-lyase activity of monkey and human CYP17A1 and reduced serum androgen levels in vivo in monkeys. These findings suggest that orteronel may be an effective therapeutic option for diseases where androgen suppression is critical, such as androgen sensitive and CRPC.

Increased serum levels of the specific advanced glycation end product methylglyoxal-derived hydroimidazolone are associated with retinopathy in patients with type 2 diabetes mellitus

Advanced glycation end products (AGEs) are thought to play a major pathogenic role in diabetic retinopathy. The most important AGE is unknown, but as increased serum methylglyoxal-derived hydroimidazolone has been demonstrated in patients with type 2 diabetes mellitus, the aim of the present study was to elucidate possible associations between serum levels of hydroimidazolone and retinopathy in patients with type 2 diabetes mellitus. We recruited 227 patients with type 2 diabetes mellitus and retinopathy ranging from none to proliferative. Level of retinopathy was determined from 7 standard field stereo photographs per eye according to the Early Treatment Diabetic Retinopathy Study. The patients were 66 +/- 11 years old, with a known diabetes duration of 14 +/- 9 years. Serum levels of hydroimidazolone were determined with a competitive immunoassay. Serum levels of hydroimidazolone were increased in nonproliferative (median, 4.50 U/mL; interquartile range, 3.69-5.77 U/mL) and proliferative retinopathy (median, 4.88 U/mL; interquartile range, 3.70-6.52 U/mL) compared with patients without retinopathy (median, 4.02 U/mL; interquartile range, 3.47-4.88 U/mL) (P = .008 and .002, respectively). There was no association between hydroimidazolone and hemoglobin A1c (r = 0.04, P = .57). In addition, patients with proliferative retinopathy and a relatively short known duration of diabetes, that is, less than the median of 14 years, had increased serum levels of hydroimidazolone (median, 6.91 U/mL; interquartile range, 4.70-8.91 U/mL) compared with those with nonproliferative retinopathy (median, 4.34; interquartile range, 3.86-5.53U/mL, P = .015). Serum levels of hydroimidazolone are increased in type 2 diabetic patients with retinopathy. This association is independent of hitherto known associated factors, such as hemoglobin A1c.

Mechanistic differences of various AT1-receptor blockers in isolated vessels of different origin

The functional inhibitory characteristics of the angiotensin II type 1 receptor blockers (ARB) candesartan; irbesartan; and losartan and its active metabolite EXP 3174 (EXP) were studied in rabbit aortic strips and rat portal vein preparations in vitro. Moreover, plasma-protein binding was determined, and the binding was high (>98. 5%) for all ARBs. These values were needed to relate the concentrations of the ARBs used in vitro to the nonprotein bound concentrations in clinical use. In both vascular preparations, candesartan caused a marked decrease in the maximal contractile response of the angiotensin II (Ang II) concentration-response curve. Losartan, EXP, and irbesartan caused a rightward parallel shift without any major effects on the maximal response to Ang II. The inhibitory effect of candesartan developed slowly (maximal effect after >30 minutes) and lasted >2 hours despite repeated washing of the vessels. The effect of losartan, irbesartan, and EXP had a faster onset, and most of the inhibitory effect disappeared after washing. The duration of the inhibitory effects of the ARBs were not related to lipophilicity of the compounds. Cooling of the rat portal vein preparations to 4 degrees C before administration of candesartan prevented the persistent inhibition of Ang II response seen at 37 degrees C. For the other ARBs studied, the magnitude of inhibition and the speed of recovery of the Ang II response were independent of the incubation temperature before washing. In addition, when candesartan was given to conscious rats, the inhibitory effect on Ang II-induced blood pressure responses persisted during the 24-hour period despite nondetectable plasma concentrations of candesartan at 24 hours. It is concluded that functional inhibitory characteristics of candesartan differ from those of the other ARBs tested. At clinically relevant concentrations, candesartan is an insurmountable and long-lasting antagonist of the vascular contractile responses to Ang II.

Cytokine mRNA decay is accelerated by an inhibitor of p38-mitogen-activated protein kinase

OBJECTIVE

To identify the site(s) in tumor necrosis factor (TNFalpha), interleukin-6 (IL-6), and macrophage inflammatory protein-1alpha (MIP-1alpha) biosynthesis that is blocked by SB202190, a selective inhibitor of p38-mitogen activated protein kinase (p38).

MATERIALS

Human blood monocytes isolated by centrifugal elutriation.

METHODS

Monocytes were stimulated with lipopolysaccharide in the presence of 0, 0.3, 1 and 3 microM SB202190. Induced TNFalpha, IL-6, and MIP-1alpha protein and mRNA were measured by ELISA and quantitative RT-PCR, respectively. The half-lives of cytokine mRNA levels were determined following treatment of cells with actinomycin D or SB202190.

RESULTS

SB202190 suppressed >60% of lipopolysaccharide-induced TNFalpha, IL-6, and MIP-1alpha protein and mRNA expression. Suppressed mRNA levels could be attributed to a >2 to 7-fold reduction in cytokine mRNA half-lives. In contrast, SB202190 did not destabilize mRNAs encoding interferon-induced gene 15 protein and glyceraldehyde-3-phosphate dehydrogenase.

CONCLUSIONS

Specific mRNA destabilization represents an important and novel site of action for the cytokine suppressive effects of p38 inhibitors.

Pharmacokinetics of CS-866, a New Angiotensin II Receptor Blocker, in Healthy Subjects

CS-866, a novel angiotensin II receptor blocker, is rapidly and completely metabolized to RNH-6270, its active metabolite. The pharmacokinetics of RNH-6270 following oral CS-866 or intravenous RNH-6270 administration was determined in 104 healthy male volunteers. The pharmacokinetics of RNH-6270 was linear over dose ranges of 1 to 32 mg (intravenous RNH-6270 administration) and 10 to 160 mg (oral CS-866 administration). The time to maximum plasma concentration of RNH-6270 after oral CS-866 administration ranged from 1.4 to 2.8 hours, and the terminal elimination half-life ranged from 12 to 18 hours. Absolute bioavailability of RNH-6270 after oral administration of CS-866 was 26%. Administration of CS-866 once daily for 10 days did not result in drug accumulation. When administered intravenously, RNH-6270 has a volume of distribution of 15 to 25 L. Approximately 35% to 50% of RNH-6270 is excreted unchanged in the urine. CS-866 was safe and well tolerated at doses of up to 160 mg/day.

Plasma concentration and E.E.G. after various regimens of etomidate

Etomidate was injected i.v. within 10 or 60 s at various doses. After etomidate 0.3 mg kg-1 the plasma concentration was 1.6 micrograms ml-1 at 1 min after the end of injection. For about 7 min a good hypnotic effect (stages C0-D2) was observed on the e.e.g. recording. For surgical procedures, however, a combination with analgesic drugs appeared to be necessary. When the dose of etomidate was increased (0.1-0.4 mg kg-1) a linear increase in plasma concentration and slow e.e.g. activity was observed concomitantly. Anaesthesia could be prolonged with additional injections or with continuous infusion. Each additional injection produced a steep increase in concentration of short duration with marked deepening of hypnosis. The infusion induced only a moderate increase in plasma concentration, whereas the depth of sleep during the period of infusion remained nearly the same. E.e.g. changes induced by etomidate are similar to those after barbiturates and other i.v. anaesthetics.