Pharmacokinetics of therapeutic doses of tropisetron in healthy volunteers

AIMS

To establish the bioavailability of tropisetron (5 mg) administered orally as capsule compared with 2 mg given intravenously.

METHODS

Using a randomized crossover design, 18 healthy volunteers received a single oral dose of tropisetron (5 mg) and an intravenous bolus of tropisetron (2 mg) separated by a wash-out period of 1 week. Plasma concentrations of tropisetron were determined by h.p.l.c. and the pharmacokinetic parameters were estimated.

RESULTS

The mean pharmacokinetic parameters for 5 mg tropisetron given orally were Cmax 3.46 ng ml(-1), t(max) 2.6 h, t(1/2) 5.7 h and AUC(0,infinity) 32.9 ng ml(-1) h. After intravenous administration initial plasma concentration was 15.1 ng ml(-1), t(1/2) 5.6 h, AUC(0,infinity) 20.7 ng ml(-1) h, V 678 l and CL 1800 ml min(-1). An inverse correlation was demonstrated between CYP2D6 activity, measured by the sparteine metabolic ratio, and the bioavailability (mean 0.60, range 0.27-0.99) of oral tropisetron.

CONCLUSIONS

Tropisetron exhibits a wide range of oral bioavailability at therapeutic doses, which is mainly determined by CYP2D6 activity.

Determination of opipramol in human plasma by high-performance liquid chromatography with photometric detection using a cyanopropyl column

A high-performance liquid chromatographic method is described for the determination of opipramol in human plasma. Opipramol was extracted into tert.-butylmethyl ether, separated on a cyanopropyl silica column and detected at 254 nm. Imipramine was used as internal standard. The limit of quantitation was 250 pg/ml using 1.5 ml plasma. Precision was better than 9%, inaccuracy less than 8%. The assay is more sensitive than previously published methods, and it has been applied to the analysis of plasma samples from a pharmacokinetic study.

Effect of tropisetron on circulating catecholamines and other putative biochemical markers in serum of patients with fibromyalgia

OBJECTIVE

The aim of the study was to assess the influence of the 5HT3-receptor antagonist tropisetron on circulating catecholamines as biochemical markers of the activity of the sympathoadrenal system in fibromyalgia. Moreover, serum concentrations of serotonin, somatomedin C, oxytocin, calcitonin-gene-related-peptide, calcitonin and cholecystokinin were assayed as putative markers in pain-related disorders like primary fibromyalgia.

METHODS

In 96 patients, who met the ACR classification criteria for fibromyalgia, and in 20 sex and age matched controls concentrations of dopamine, noradrenaline, adrenaline, serotonin and tropisetron were assayed in serum by HPLC with electrochemical detection. All other transmitters were determined by ELISA.

RESULTS

There was with the exception of tropisetron, calcitonin and dopamine, no correlation between doses of tropisetron 5, 10, 15 mg respectively and significant changes in circulating transmitters or other transmitters as putative biochemicals markers in primary fibromyalgia. Regarding the prediction of pain reduction to tropisetron, patients with elevated dopamine and/or reduced plasma 5-HT concentrations tended to show a higher response rate.

CONCLUSION

Despite these partly disappointing results another prospective pilot study with selected patients vs. age and sex matched controls, double blind and with comparison of other 5HT3-receptor antagonists e.g. dolasetron and granisetron e.g. after i.v. bolus injection is suggested. Still the data obtained in this preliminary paper provide some evidence regarding the present discussion on subgroups of patients with primary fibromyalgia.

Pharmacokinetic interaction between proton pump inhibitors and roxithromycin in volunteers

BACKGROUND

Triple therapy including two antibiotics and a proton pump inhibitor is a rational approach to the treatment of Helicobacter pylori induced peptic ulcer disease. The interaction of antimicrobial therapy and acid suppression is not yet well elucidated.

AIMS

To investigate the effects of proton pump inhibitors on roxithromycin levels in plasma and gastric tissue under steady-state conditions in volunteers.

METHODS

In two crossover studies omeprazole 20 mg b.d., lansoprazole 30 mg b.d., roxithromycin 300 mg b.d., and the combination of roxithromycin with either omeprazole or lansoprazole were administered to 12 healthy volunteers over 6 days. Blood plasma levels of the drugs were measured. In addition, roxithromycin concentrations were also determined in gastric juice and gastric tissue obtained during endoscopy.

RESULTS

The proton pump inhibitors and roxithromycin did not alter the blood plasma pharmacokinetics of each other. When compared to roxithromycin administered alone, its combination with a proton pump inhibitor significantly increased the roxithromycin concentrations in gastric juice (3.0-5.0 microg/mL vs. 0.3-0.4 microg/mL) and gastric tissue (antrum: 3.8-4.0 vs. 2.8 microg/g, fundus: 5.9-7.4 vs. 4.2-4.4 microg/g).

CONCLUSIONS

Proton pump inhibitors and roxithromycin do not alter the systemic bioavailability of each other. However, proton pump inhibitors increase the local concentration of roxithromycin in the stomach which may contribute to the clinically proven synergic beneficial action in eradication therapy of H. pylori.

Bioavailability of cefpodoxime proxetil with co-administered acetylcysteine

In a cross-over study on twelve healthy volunteers cefpodoxime proxetil (CAS 87239-81-4) and acetylcysteine (CAS 616-91-1) were evaluated for possible pharmacokinetic interactions. After a standardized breakfast, the subjects received p.o. either 200 mg cefpodoxime administered as cefpodoxime proxetil (reference) or 200 mg cefpodoxime and 200 mg acetylcysteine (test). To determine the pharmacokinetic profile of cefpodoxime the plasma concentrations were determined by HPLC. The plasma concentration-time curve of cefpodoxime was very similar after both regimens, and with respect to cefpodoxime bioequivalence has been proven. The narrow range of 90% confidence intervals for the quotient test/reference for Cmax and AUC indicate reliable bioavailability of cefpodoxime proxetil independent of co-administered acetylcysteine.

Simultaneous determination of acetylsalicylic acid and salicylic acid in human plasma by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of acetylsalicylic acid (ASA) and its main metabolite salicylic acid (SA) in human plasma. Acidified plasma is deproteinized with acetonitrile which is separated from the aqueous layer by adding sodium chloride. ASA and SA are extracted into the acetonitrile layer with high yield, and determined by reversed-phase HPLC (column: Novapak C18 4 microns silica, 150 x 4 mm I.D.; eluent: 740 ml water, 900 microliters 85% orthophosphoric acid, 180 ml acetonitrile) and photometric detection (237 nm). 2-Methylbenzoic acid is used as internal standard. The method allows the determination of ASA and SA in human plasma as low as 100 ng/ml with good precision (better than 10%). The assay was used to determine the pharmacokinetic parameters of ASA and SA following oral administration of 100-500 mg ASA in healthy volunteers.

Serum and cellular pharmacokinetics of clarithromycin 500 mg q.d. and 250 mg b.i.d. in volunteers

In an open-label, randomized, crossover study 12 healthy volunteers were given clarithromycin orally 250 mg twice daily (b.i.d.) and 500 mg once a day (q.d.). Blood and saliva samples were collected on study days 1 and 5 to determine the pharmacokinetics of clarithromycin and its 14-hydroxy metabolite in plasma and saliva, and to measure concentrations of clarithromycin in mononuclear cells (MNCs) and polymorphonuclear leucocytes (PMNs). The mean peak levels of clarithromycin on day 5 of therapy in serum (2.3 vs. 1.2 mg/l), saliva (1.1 vs. 0.3 mg/l) and blood cells 60 vs. 26 mg/l in MNCs and 29 vs. 14 mg/l in PMNs) were at least doubled, the trough levels were lower with 500 mg q.d. vs. 250 mg b.i.d. (0.09 vs. 0.28 mg/l in serum; 0.06 vs. 0.13 mg/l in saliva; < 1 vs. 6.8 mg/l in MNCs; 0.8 vs. 2.8 mg/l in PMNs). The mean relative peak serum concentrations of the 14-hydroxy metabolite were somewhat lower with the 500 mg dosage (0.78 vs. 0.46 mg/l). The peak concentrations of clarithromycin and its 14-hydroxy metabolite in saliva were 25-40% and 50-80% of the maximum serum concentrations with both dosage regimens. Clarithromycin exhibits good and rapid penetration into intracellular as well as into extravasal extracellular body compartments. Clarithromycin 500 mg q.d. compares favourably with 250 mg b.i.d., as far as peak serum levels and bioavailability are concerned, but trough levels are lower at the end of the 24-hour dosing interval.

Cardiovascular parameters and catecholamines in volunteers during passive orthostasis. Influence of antihypotensive drugs

To evaluate the therapeutic value of various antihypotensive agents we investigated amezinium (AMZ; CAS 30578-37-1), dihydroergotamine (DHE; CAS 511-12-6), midodrine (MDD; CAS 42794-76-3), and oxilofrine (OXF; CAS 365-26-4) in volunteers during passive orthostasis in a randomized double-blind study against placebo (PCB). Blood pressure, heart rate, and circulating catecholamines were determined before and after i.v. injections of the mentioned agents before and during 10 min of passive orthostasis. Echocardiographic and venous plethysmographic data were obtained during resting before and after the administration of the drugs. Resting heart rate decreased after injection of PCB, AMZ, DHE, and MDD. During tilting no significant changes in heart rate could be observed. Blood pressure remained unchanged at rest and during orthostasis after all agents injected. DHE and MDD lowered circulating noradrenaline. Echocardiographic parameters were changed after administration of AMZ (increase in stroke volume index (SVI) and ejection fraction (EF)), MDD (increase in enddiastolic volume index and SVI), and OXF (increase in SVI, EF, and cardiac index). The venous capacity of the lower left leg was only significantly decreased after injection of DHE, indicating an increased venous tone of the leg veins. The observed changes in sympathetic and cardiovascular parameters are in agreement with their sympathomimetic actions and allow a differential therapeutic classification: DHE and MDD are suitable agents for patients with sympathotonic orthostatic reaction; if asympathotonic orthostatic reaction occurs MDD, AMX and OXF should be recommended to those patients.

Comparative investigations on the bioavailability of cefuroxime axetil

In a three-way cross-over study the bioavailability of cefuroxime was determined in 12 healthy volunteers after oral administration of 250 mg as cefuroxime axetil (Elobact; CAS 64544-07-6) in a plain aqueous suspension and as tablets from different batches. The tablet formulations showed nearly identical pharmacokinetic parameters and were bioequivalent. The mean maximum serum concentration was 4.7 micrograms/ml, achieved after 2.1 h. The serum half-live was 1.2-1.4 h, the area under the serum concentration-time curve was 14.3-14.4 micrograms/ml.h and the urinary recovery of unchanged cefuroxime was 54%. The bioavailability of cefuroxime after administration of cefuroxime axetil in aqueous suspension was lower, but bio-inequivalence was not demonstrated.

Skin tissue fluid levels of cefotiam in healthy man following oral cefotiam hexetil

Cefotiam hexetil is a pro-drug of cefotiam available for oral administration. To evaluate cefotiam concentrations at the active site in skin and soft-tissue infections, drug levels in skin suction blister fluid (SBF), cantharides blister fluid (CBF) and serum were determined. Six healthy subjects received oral cefotiam 400 mg as cefotiam hexetil. On an other day 200 mg was injected intravenously. Following the oral dose, the bioavailability of cefotiam was 45.5%, and the maximum concentration in serum of 2.6 mg.l-1 was obtained at 2.1 h. Peak concentrations in both types of blister fluid (0.9 mg.l-1) were significantly lower than after the iv dose (SBF 1.4 mg.l-1, CBF 1.5 mg.l-1), and the peak levels occurred later (3.3 versus 1.5 h in CBF). Despite the delay, the extent of penetration was about 100% following either mode of administration (SBF, iv dose 112%, oral dose 117%). The cefotiam level in skin blister fluids declined significantly more slowly than the serum level. Following the oral dose, the mean terminal half life was serum 0.8 h, SBF 2.6 h and CBF 4.6 h. Cefotiam concentrations in the blister fluids were close to the MIC90 of Staphylococcus aureus, S. epidermis and H. influenzae and exceeded the MIC90 of Streptococci, E. coli and Proteus mirabilis. Thus, the oral administration of cefotiam 400 mg t.i.d. should be curative in the majority of bacterial infections of the skin and soft-tissues.

[The bioavailability of doxycycline]

The bioavailability of doxycycline (Doxy-Diolan 100 tablets, test, active substances: 100 mg doxycyclin per tablet) was compared with that of another commercially available tablet-formulation containing the same active substance (reference). In a cross-over study, 16 young healthy male volunteers were administered in fasting state orally by one tablet containing 100 mg active substance. The concentrations of doxycycline were determined in plasma and saliva by a high-performance liquid chromatographic assay. Mean maximum plasma concentration (cmax +/- standard deviation) of doxycycline were 1.57 +/- 0.40 micrograms/ml (test) and 1.59 +/- 0.38 micrograms/ml (reference), respectively, and were reached 1.47 +/- 0.55 h and 1.66 +/- 0.57 h after administration. Plasma half-lives were 16.6 +/- 2.9 h and 16.8 +/- 3.0 h, the areas under the plasma concentration-time curves (AUC0-00) 29.3 +/- 4.5 mg/l.h and 29.7 +/- 4.4 mg/l.h. The concentration of doxycycline in saliva were low, median maximum concentrations of 50 ng/ml were measured 1-2 h after administration. The statistical evaluation revealed bioequivalence between both drugs.

Relative bioavailability of three cefixime formulations

Three galenic formulations of cefixime (tablet, syrup and dry suspension) containing 200 mg each were compared with respect to their relative bioavailability in twelve healthy volunteers. All three formulations showed reliable absorption. Mean peak plasma concentrations were reached after 3.3-3.5 h, mean terminal half lives were 2.9-3.1 h. 18-24% of the dose administered were recovered unchanged in the urine. Best bioavailability was obtained with the dry suspension (AUC0-infinity = 25.8 +/- 7.0 micrograms/ml h; Cmax = 3.4 +/- 0.9 microgram/ml), followed by the tablet (AUC0-infinity = 20.9 +/- 8.1 micrograms/ml h; Cmax = 3.0 +/- 1.0 micrograms/ml) and the syrup which is based on triglycerides (AUC0-infinity = 17.8 +/- 5.9 micrograms/ml h; Cmax = 2.4 +/- 0.7 micrograms/ml). The statistical analysis resulted in bioinequivalence between dry suspension and syrup. It is concluded that best bioavailability of cefixime after oral administration is guaranteed when taken in an "aqueous medium" either as dry suspension or as tablet with "plenty of liquid".

Pharmacology and clinical pharmacology of organic nitrates

Current concepts and future aspects of pharmacological interventions in the treatment of coronary heart disease have been compiled. Especially new insights in the pathophysiology of coronary heart disease e.g. the dynamic pathology of coronary atherosclerosis, possible role of endothelin in vasospasm, as well as new pharmacodynamic and pharmacokinetic aspects of organic nitrates are discussed. Also the role of sympathetic nervous system as a pivotal question in pathophysiology and clinical pharmacology in the treatment of angina pectoris has been considered.

Distribution and subtype determination of beta-receptors in the spinal cord of the adult rat

1. We determined the number of beta-receptors in the whole spinal cord of the adult rat and in the cervical, thoracal, and lumbal/sacral parts. 2. The undivided spinal cord contains 47 +/- 10 fmol/mg beta-receptors (KD = 2066 +/- 982 pmol/liter), and the cervical part of the spinal cord contains 53 +/- 8 fmol/mg protein (KD = 3224 +/- 1775 pmol/liter). The thoracal part shows 40 +/- 1 fmol/mg protein (KD = 3229 +/- 104 pmol/liter), and the lumbal/sacral spinal cord contains 48 +/- 8 fmol/mg protein (KD = 3610 +/- 1610 pmol/liter). 3. Competitive inhibition studies with l-practolol, dl-atenolol, and ICI 118,551 were performed and we calculated by a computer program in the whole spinal cord the following ratio of beta-receptor subtypes: 80 +/- 5% Beta 1-receptors and 20 +/- 5% beta 2-receptors. 4. The basal and (-)-isoproterenol- and NaF-stimulated activity of adenylate cyclase was highest in the cervical part of the spinal cord and equally distributed between the thoracal and the lumbal/sacral parts. 5. The whole synaptosomal protein of the cervical part of the spinal cord contained 132 +/- 20 fmol, the thoracal part 117 +/- 3 fmol, and the lumbal/sacral part 133 +/- 22 fmol.

Pharmacokinetics of ciprofloxacin in elderly patients

For perioperative prophylaxis 200 mg ciprofloxacin were administered as a short intravenous infusion to 17 patients aged 57-84 years before transurethral resection (TUR-P) or transvesicular enucleation (TVP) of the prostate. 13 patients were injected simultaneously with 2.5 g ioxitalamic acid i.v. to determine the kidney function. In 11 patients the plasma concentrations were assayed and the pharmacokinetic parameters calculated. At the end of infusion the concentrations of ciprofloxacin in plasma reached 4.2 +/- 0.8 microgram/ml and decreased after a fast distribution period (plasma half-life 0.20 +/- 0.09 h) with a terminal half-life of 4.2 +/- 1.3 h to 0.2 +/- 0.09 microgram/ml after 10 h. The apparent volume of distribution in steady state was 183 +/- 45% of body weight, the plasma clearance 457 +/- 146 ml/min/70 kg. The average concentrations in prostatic adenoma tissue were at all sampling times higher (2fold) than in plasma. The mean concentrations in prostatic secretion were about half of the respective plasma concentrations. High concentrations of the concomitantly administered ioxitalamic acid in prostatic secretion are considered as an indicator of urinary contamination. In those patients high ciprofloxacin concentrations in prostatic secretion are not reliable.

In-vitro activity of fleroxacin against isolates causing complicated urinary tract infections and concentrations in seminal and prostatic fluid and in prostatic adenoma tissue

Fleroxacin is a new fluoroquinolone with a broad antibacterial spectrum and a serum half-life of about 8-12 h. Eighty percent of 400 isolates from complicated or hospital-acquired urinary tract infections were inhibited by a concentration of 1 mg/l and 95% by 4 mg/l. As with other quinolones, fleroxacin is less active in acid urine (pH 5.4) than in Mueller-Hinton broth (pH 7.4). In 12 healthy volunteers the concentrations of fleroxacin were measured in plasma and seminal and prostatic fluid 2, 4 and 12 h after an oral dose of 400 mg. The mean plasma concentrations of three or four volunteers at each time were 4.2, 3.6 and 1.2 mg/l, respectively. The corresponding prostatic fluid/plasma ratios were 0.30, 0.27 and 1.96, respectively. By concomittant administration of ioxitalamic acid it could be demonstrated that in samples obtained 12 h after administration urinary contamination must be considered. Fleroxacin is concentrated in seminal fluid by a median ratio of 1.7. In 13 elderly patients the prostatic fluid and prostatic adenoma tissue concentrations were determined one to four hours following oral administration of 400 mg. The concentrations in prostatic fluid were similar to those of volunteers. The tissue concentrations exceeded plasma concentrations by only about 10% (median). Fleroxacin is very active against isolates causing complicated UTI. Concentrations in seminal and prostatic fluid and prostatic adenoma tissue are sufficiently high to treat bacterial prostatitis or vesiculitis caused by susceptible bacterial strains.

Beta-adrenergic receptors and enzymes in rat myocardial membranes: implications of fractionation procedures and beta-adrenoceptor antagonists

1. We performed an enzymatic characterization of two different fractionation procedures of ventricles from rat hearts. The enzymatic assays covered succinic dehydrogenase as a marker for inner mitochondrial membranes, monoamine oxidase as a marker for outer mitochondrial membranes, NADPH-cytochrome c reductase and RNA as endoplasmatic reticular markers, acid phosphatase as a lysosomal marker, and lactic dehydrogenase as a marker for the "soluble" compartment; DNA was estimated for nuclear contamination. 2. The plasma membrane markers 5'-nucleotidase, Ca2+-ATPase, Mg2+-ATPase, Na+-K+-ATPase, and adenylate cyclase were determined. 3. The roughly prepared membrane fractions showed increased yields of the membrane markers; the number of beta receptors, determined with (-)-[3H] dihydroalprenolol and DL-propranolol, amounted to 68 +/- 6 fmol/mg protein (KD = 3390 +/- 450 pmol, Hill coefficient = 1.5). 4. The membrane fraction prepared with a linear sucrose gradient showed an increased inner mitochondrial membrane marker; presumably the outer mitochondrial membrane was stripped off. The beta-receptor number was 39 +/- 3 fmol/mg protein (KD = 6250 +/- 300 pmol; Hill coefficient = 1.2).

Penetration of fleroxacin into prostatic secretion and prostatic adenoma tissue

In 12 elderly patients, plasma, prostatic secretion and adenoma tissue concentrations of fleroxacin were determined 1-4 h following oral administration of 400 mg. The plasma concentrations ranged between 0.4 and 5.5 micrograms/ml (median 3.7 micrograms/ml), the mean tissue concentrations were slightly higher. The concentrations in prostatic secretion were about one third of the simultaneous plasma concentrations. High concentrations of the concomitantly administered ioxithalamic acid in prostatic secretion are considered as indicative of urinary contamination, and in this case the fleroxacin concentrations are questionable. The drug levels in prostatic adenoma tissue were similar to the concomitantly measured plasma levels.

The absolute systemic availability of a new oral formulation of co-dergocrine in healthy subjects

We have studied the absolute systemic availability (f) of an oral formulation (Hydergin spezial = Hydergine FASR 4 mg per tablet) of co-dergocrine by three different methods. Twelve healthy volunteers received single doses of 0.9 mg co-dergocrine intravenously and 8.0 mg orally in a randomized crossover design. The pharmacological effect of co-dergocrine was monitored as a reduction in plasma prolactin. Maximal plasma concentrations of co-dergocrine after oral dosing ranged between 0.181 and 1.307 ng.ml-1. Maximal urinary excretion ranged between 4.7 and 9.9 micrograms.h-1 and between 0.3 and 2.3 micrograms.h-1 after intravenous and oral doses respectively. Clearance was measured as 90 +/- 22 l.h-1 and the absolute systemic availability (f) as 2.25 +/- 0.65% by using the areas under the plasma concentration-time curves extrapolated to infinity. Calculation of f by comparing areas up to 32 h or the fractions of the dose excreted in urine led to identical results. The intravenous and oral doses produced similar pharmacological effects (reduction of plasma prolactin concentrations) despite the small value of f.

[Bioavailability of heptaminol in healthy subjects]

In ten healthy volunteers the plasma and urine concentrations of heptaminol (Heptylon) were determined by high-performance liquid chromatography after intravenous administration of 250 mg heptaminol and oral intake of 2 x 150 mg heptaminol in tablet form, and the pharmacokinetic parameters were calculated. Heptaminol was rapidly and entirely absorbed following oral administration of heptaminol. Mean plasma peak concentrations of 1.6 mg/l were reached after 1.8 h, the area under the plasma concentration-time curve was equal to that after intravenous administration. The dominant terminal plasma half-life was 2.5-2.7 h. The total clearance amounted to 700 ml/min, and nearly all the dose given was recovered unchanged in urine within 24 h, indicating renal elimination by glomerular filtration and tubular secretion without metabolization.

[The bioavailability of midodrin and alpha-2,5-dimethoxyphenyl-beta-aminoethanol hydrochloride]

The pharmacokinetics of midodrin (alpha-2,5-dimethoxyphenyl-beta-glycinamidoethanol hydrochloride, ST 1085) and its main metabolite ST 1059 (alpha-2,5-dimethoxyphenyl-beta-aminoethanol hydrochloride) have been investigated in 12 male healthy volunteers. 2.5 mg midodrin hydrochloride were applied intravenously, as drinking solution or as tablet (Gutron) according to a randomized cross-over design. Plasma and urine samples collected up to 24 h after application were analyzed by high-performance liquid chromatography with fluorescence detection. The mean maximum concentration in plasma for midodrin was ca. 10 ng/ml 20-30 min after oral administration, for ST 1059 ca. 5 ng/ml after 1 h. Midodrin was eliminated with a terminal half-life of 0.5 h. The half-life of ST 1059 was determined to be 3 h. The mean area under the plasma-level vs. time curve (AUC) of ST 1059 after administration of 2.5 mg midodrin i.v. was 28.7 ng X h/ml, and as drinking solution or as tablet 25.7 and 25.6 ng X h/ml, respectively. The data of 10 volunteers could be used for the calculations of the bioavailability of ST 1059 by the AUC. Assuming an interval of equivalence of 0.75-1.25 because of the relatively small number of volunteers, the three galenical formulations are considered to be equivalent.

Inhibition of monoamine oxidase by viloxazine in rats

Biochemical and pharmacological investigations about the effect of the antidepressant drug viloxazine (Vivalan) on catecholamine metabolism in rats led to the following results: Viloxazine exerts a dose and time dependent inhibition of monoamine oxidase activity of brain and liver mitochondrial fraction and tissue homogenates of hypothalamus, heart, liver, and adrenal glands, both in vitro and after oral and parenteral administration in vivo. Consequently, an increase in catecholamine concentrations in brain of rats could be observed after pretreatment with viloxazine. In addition brain serotonin concentrations rose and 5-hydroxy-indoleacetic acid was diminished. However, characterization of inhibition of monoamine oxidase activity by viloxazine in vitro revealed: Compared to the specific inhibitors clorgyline for MAO-A- and pargyline for MAO-B-activity, viloxazine was a very weak inhibitor both for MAO-A and MAO-B in vitro. The type of inhibition was competitive and reversible. From the presented results and the results obtained by other laboratories it is concluded that inhibition of monoamine oxidase activity by viloxazine, although clearly demonstrated in animal experiments, may not be the only mechanism for an antidepressant action of the drug in man.

Pharmacokinetics, in-vitro activity, therapeutic efficacy and clinical safety of aztreonam vs. cefotaxime in the treatment of complicated urinary tract infections

The minimal inhibitory concentrations (MICs) of aztreonam and cefotaxime were determined against 400 isolates from urological in-patients with complicated and/or hospital acquired urinary tract infections (UTI). Against the Gram-negative rods the activities of both antibiotics were comparable except for higher activity of aztreonam against Pseudomonas aeruginosa. The pharmacokinetic study in nine elderly patients showed a prolonged plasma half life of aztreonam (2.7 h) as compared to younger volunteers (1.6-1.9 h). In a prospective randomized study 39 urological patients with complicated and/or hospital acquired UTI were treated with 1 g aztreonam or cefotaxime iv twice daily for 4 to 15 days. Cure was obtained in 5 out of 18 patients in the aztreonam and 7 out of 20 patients in the cefotaxime group. There were 3 superinfections, 7 relapses and 3 reinfections in the aztreonam group and 1 failure, 1 superinfection, 6 relapses and 5 reinfections in the cefotaxime group. There was no significant difference in therapeutic efficacy between the two antibiotics. Both antibiotics were tolerated well and seem to be equally effective in the treatment of complicated UTI caused by sensitive organisms.

Circulating and tissue catecholamines in rats with chronic neurogenic hypertension

To study the role of peripheral catecholamines in plasma and different tissues in neurogenic hypertension we measured directly blood pressure, maximum rate of left ventricular pressure rise (dp/dtmax) and heart rate through an aortic catheter 5 weeks after total sino-aortic baroreceptor deafferentation in male Sprague-Dawley rats. Blood samples were collected through the same catheter to determine plasma catecholamine concentrations. Blood pressure and dp/dtmax were significantly higher in neurogenic-hypertensive rats when compared with sham operated rats. Plasma noradrenaline concentrations and plasma adrenaline concentrations reached significantly higher levels in neurogenic-hypertensive rats. In the heart noradrenaline content was lower (when calculated per g wet weight) and in the adrenal medulla adrenaline content was higher in neurogenic-hypertensive rats, when compared with sham operated controls. A significant positive correlation was found between dp/dtmax and plasma noradrenaline concentrations. It is concluded that sino-aortic baroreceptor deafferentation produces a significant chronic hypertension, probably supported by elevated plasma catecholamine concentrations and enhanced synthesis and release of adrenaline from adrenal medulla.

Changes in plasma catecholamine concentrations in patients with coronary heart disease during pacing and physical exercise

To study the difference in sympathetic activity during pacing the right atrium or during physical exercise in patients with coronary heart disease, we investigated circulating plasma catecholamine concentrations in the coronary sinus and brachial artery radioenzymatically in 11 male patients with well documented coronary artery disease. Heart rate was increased stepwise 20 beats/min from 90 beats/min up to 150 beats/min by pacing the right atrium and physical exercise was performed by increasing work load stepwise by 25 from 25 up to 100 W on an ergometric bicycle. Plasma noradrenaline and adrenaline concentrations were increased significantly only during physical exercise. In addition, there was an increase in arterial-coronary sinus noradrenaline difference during graded physical exercise, whereas no further release of noradrenaline from the myocardium occurred during pacing. An enhanced cardiac sympathetic tone in patients with coronary heart disease is discussed. It is suggested that atrial pacing is not an adequate stimulus evoking an overall increase of cardiac and peripheral sympathetic tone.

Effects of nicotine and its major metabolites on blood pressure in anaesthetized rats

Blood pressure and heart rate in anaesthetized rats has been determined after i.v. injection of increasing doses of nicotine (NI) and its major metabolites, i.e. continine (CO), nornicotine (NOR), metanicotine (MN) and dihydrometanicotine (DMN). NI and MN elicited similar dose response curves, increasing blood pressure according to the dose injected. However, the dose response curve of MN was shifted to the right. Furthermore DMN caused similar pressor effects than MN and the pressor effects of NOR was even weaker. Only after injection of CO was a dose-dependent depressor effect observed and this was reversed after very high doses. CO also reduced heart rate in a dose-dependent manner, whereas NI and its other metabolites did not significantly change heart rate.

Sympathoadrenal dysfunction in rats with chronic neurogenic hypertension

Compared to sham-operated controls 5 weeks after surgery neurogenic hypertensive rats with sino-aortic baroreceptor deafferentation had higher blood pressure, higher plasma noradrenaline and adrenaline levels, lower heart noradrenaline concentrations, higher adrenomedullary adrenaline levels and increased cardiac intraventricular pressure (dp/dtmax).

High-performance liquid chromatographic analysis of cefotetan epimers in human plasma and urine

Cefotetan, a new broad-spectrum 7 alpha-methoxycephalosporin antibiotic, was assayed in plasma and urine by means of reversed-phase high-performance liquid chromatography. Commercially available cefotetan exists in two epimeric forms. The procedure described allows the separation and quantitation of both epimers. For the first time a different pharmacokinetic behaviour (t1/2 = 3 h versus 4 h) for each epimer after intravenous injection to healthy volunteers is demonstrated. It is assumed that one epimer is bound to a greater extent to serum proteins and is therefore responsible for the differences observed. As both epimers exhibit similar antibacterial activity, it seems doubtful whether these differences would have clinical significance. Iothalamic acid was determined simultaneously as a marker of kidney function.

Changes in peripheral and central catecholaminergic and serotoninergic neurons of rats after acute and subacute administration of nicotine

To establish dose-response relationships for nicotine (acute and subacute administration), we measured hemodynamic parameters as well as circulating and tissue catecholamines in sympathetically innervated organs in rats. We also investigated nicotines's influence on adrenoceptor binding sites of the heart and on serotonin metabolism. In conscious and anesthetized rats, we found a dose-dependent increase in circulating catecholamines after acute injection of nicotine. At low doses nicotine released norepinephrine, resulting in a decrease of blood flow and heart rate, whereas high doses of nicotine released epinephrine, resulting in a reversal of the cardiovascular parameters investigated. In the heart norepinephrine concentration increased after nicotine application. In the lung epinephrine rose markedly, whereas serotonin and 5-hydroxyindolacetic acid were diminished. After subacute administration of nicotine the number of binding sites for 3H-Dihydroalprenolol in the heart was significantly reduced, whereas norepinephrine content was increased. Dopamine, serotonin, and 5-hydroxyindolacetic acid were increased in the hypothalamus. Our findings show that nicotine not only affects peripheral and central catecholaminergic neurons, but also central serotoninergic neurons, thus enhancing turnover of these amines.

Ceftazidime: pharmacokinetics in young volunteers versus elderly patients and therapeutic efficacy with complicated urinary tract infections

Thirty-six urological patients (21 male, 15 female) aged 21 to 83 years with complicated and/or hospital-acquired urinary tract infections due to sensitive bacteria were treated with ceftazidime intravenously with a daily dose of 2 g bd over 5 to 17 days. Twenty-seven patients were followed for 1 to 4 weeks after therapy. Cure was observed in 41%, reinfection in 33% and relapse in 26% of the patients. Eradication of the original pathogen occurred in 74%. Five patients showed minor side effects: diarrhoea (2), nausea (1), rash (1), headache (1). No signs of renal, hepatic or haematological toxicity were observed. A pharmacokinetic study was performed in 13 elderly patients aged 63 to 83 years on day 1 of treatment and in 6 volunteers aged 24 to 32 years following administration of 2 g of ceftazidime as short intravenous infusion. The mean serum half life in 12 patients 2.9 h significantly higher than in volunteers (1.75 h). Serum concentrations in patients on day 7 of treatment, however, showed no accumulation when treated with a dosage of 2 g bd.

Transmitter-peptide coexistence in the central nervous system

In this minireview about transmitter coexistence situations in central nervous system and peripheral sympathetically innervated tissues, the classical transmitters, dopamine, noradrenaline, adrenaline and serotonin, together with peptides such as substance P, cholecystokinin and avian pancreatic polypeptide, have been considered. The specificity of an immunohistochemical reaction for the identification of peptides and functional aspects of central transmitter peptide coexistence are discussed. In conclusion, in several experimental models it has been demonstrated that peptides, which are known to coexist with monoamines, exert specific effects in those regions where coexistence situations have been reported. In general, the effect of the co-stored peptides seems to be enhancement of the response caused by monoamines, indicating that two coexisting neuroactive substances cooperate in causing a certain physiological response.

Induction of anesthesia with halothane increases plasma norepinephrine concentrations

In seven unstimulated, unmedicated patients given halothane/O2 via face mask, plasma norepinephrine concentration increased 15 min after induction and returned to control at 45 to 60 min. Changes in plasma norepinephrine levels did not correlate with changes in cardiovascular variables. In 10 additional awake, unpremedicated patients, plasma norepinephrine concentration did not change during 5 min of application of 100 per cent oxygen via face mask, but rose with subsequent administration of halothane and nitrous oxide. Again, changes in plasma norepinephrine did not correlate with changes in cardiovascular variables. The authors perfused seven isolated cat spleens with a Krebs-Ringer's lactate solution. Addition of 0.01 atm halothane to the perfusate initially increased release of norepinephrine into the effluent. The authors conclude that halothane or halothane-nitrous oxide initially increases plasma norepinephrine during induction of anesthesia. This increase is not due to the placement of a face mask, but may relate to an effect of halothane at sympathetic nerve endings.

Elevated plasma catecholamines in young hypertensive and hyperkinetic patients: effect of pindolol

1 The sympathetic nervous system plays an important role in the regulation of blood pressure. Plasma catecholamine concentrations are considered to be reliable indices of sympatho-neuronal (noradrenaline) and sympatho-adrenal (adrenaline) activity and reactivity in man.

2 Sympathetic and adrenal activity and reactivity in young patients with essential hypertension or hyperkinetic heart syndrome were compared with an appropriate control group matched for age. The groups of hypertensive patients and patients with hyperkinetic heart syndrome could be clearly distinguished from control subjects on the basis of circulating catecholamine levels at rest.

3 A clear-cut increase in circulating noradrenaline and adrenaline was observed in young patients with essential hypertension and hyperkinetic heart syndrome at rest. Clinically, hypertensive patients were characterized by elevated systolic and diastolic blood pressure and increased heart rate, whereas patients with hyperkinetic heart syndrome had increased heart rate and increased systolic blood pressure, whereas diastolic blood pressure was normal. At rest, there was a significant positive correlation between heart rate and circulating catecholamines in both groups of patients. In hypertensives a positive correlation between heart rate and plasma adrenaline concentrations, in patients with hyperkinetic heart syndrome a positive correlation between heart rate and plasma noradrenaline concentrations could be observed. In addition a positive correlation between plasma noradrenaline concentrations and systolic blood pressure in all groups of patients studied, was obtained.

4 Sympatho-neuronal and sympatho-adrenal reactivity during mental stress or physical exercise increased in both groups of patients, mirrored by an increase in blood pressure and heart rate.

5 Pindolol, a potent non-selective β-adrenoceptor blocking drug with intrinsic sympathomimetic activity and minimal membrane stabilizing properties, administered in a single oral dose of 10 mg, diminished the exaggerated sympathetic tone in both groups of patients by attenuating circulating catecholamine levels at rest or during mental stress, but not during physical exercise.

Plasma noradrenaline correlates to sympathetic muscle nerve activity in normotensive man

Recordings of multiunit sympathetic activity were made in muscle branches of the peroneal nerve in 22 healthy subjects at rest in recumbent position. Nerve activity was quantitated in terms of burst incidence (number of pulse synchronous sympathetic bursts per 100 heart beats or per min). In a separate session, 4-45 months later, blood was drawn from an antecubital vein for noradrenaline analysis. Both sympathetic activity and plasma concentrations of noradrenaline varied widely between subjects and both parameters increased with age. There was a significant positive correlation between a subject's level of sympathetic activity and his plasma concentration of noradrenaline. It is suggested that overflow of transmitter from sympathetic terminals in muscles contributes significantly to plasma levels of noradrenaline at rest.

[Effects of acute beta-adrenoceptor blockage (metoprolol i.v.) on plasma norepinephrine concentration and hemodynamics in postmyocardial infarction patients]

The effect of acute beta-adrenoceptor blockage (Metoprolol) (M), 0.1 mg/kg i.v.) on left ventricular performance has been investigated at rest and during exercise in 15 patients with 2--3 months old transmural myocardial infarctions. Coronary venous and arterial norepinephrine (NE) concentrations were determined. There was no significant change in arterial and coronary venous NE concentrations (0.27 and 0.22 ng/ml, respectively) after blockage of beta-adrenoceptors (0.36 vs 0.26 ng/ml), which caused a fall of stroke volume from 79 to 68 ml, a reduction of ejection fraction from 62 to 55% and of circumferential fibre shortening form 1.2 to 0.9 circ/sec. During physical exercise the plasma NE concentration in the arterial (0.51 ng/ml) and coronary venous (0.6 ng/ml) blood increased significantly and increased even further to 0.65 and 0.76 ng/ml, respectively, following administration of Metoprolol. The arterio-coronary sinus difference in NE concentrations demonstrate a release of NE from the myocardium. As compared to control values, heart rate following Metoprolol was lower (116 vs 106/min), mean PCV pressure was slightly increased (from 21 to 23 mm Hg) and there was a fall of cardiac index from 6.3 to 5.2 l/min X m2. It is likely that the increased sympathetic activity after Metoprolol and during exercise is a compensatory reaction due to the hemodynamic effects of blockade of beta-adrenoceptors. Further studies are in preparation in order to find out if this is only a transient phenomenon during the early adaptation phase after blockade of beta-adrenoceptors.

Changes in central catecholaminergic neurons in the spontaneously (genetic) hypertensive rat

Catecholamines and catecholamine-synthesizing enzymes have been examined in specific brain areas during the development of spontaneously (genetic) hypertensive (SH) rats. Changes in catecholamine metabolism were localized to regions of the brain implicated in the regulation of blood pressure. Norepinephrine levels and dopamine-beta-hydroxylase (DBH) activities were decreased in specific nuclei of the hypothalamus and in the nucleus interstitialis striae terminalis ventralis, in both young and adult rats. The decrease in the formation of norepinephrine can result in a reduced activation of central alpha-adrenergic receptors which may be related causally to the onset of hypertension. The activity of the epinephrine-forming enzyme, phenylethanolamine-N-methyltransferase (PNMT), was increased in the A1 and A2 areas of the brainstem in young SH rats, but it was normal in adult hypertensive animals. These results implicate adrenergic neurons in the brainstem and noradrenergic neurons in the hypothalamus in the development of spontaneous (genetic) hypertension in rats.

Effect of prolonged treatment with adrenergic neuron blocking drugs on sympathoadrenal reactivity in rats

The effects of repeated high doses of the adrenergic neuron blocking drug guanethidine or a hexahydropyrazinoindole compound (2-guanyl-1,2,3,10,10a, hexahydro-1,2,a-pyrazinoindole, EMD 21192) (30 mg/kg i.p., 21.5 mg/kg i.p. respectively, equimolar doses) on sympathoadrenal activity were investigated in normotensive adult rats. During treatment for 5 weeks with either guanethidine or EMD 21192 the systemic blood pressure fell steadily. Noradrenaline content in the heart and vas deferens were decreased markedly by guanethidine and to a much less degree by EMD 21192. EMD 21192 markedly lowers the catecholamine content of the adrenal medulla, presumably as a result of inhibition of dopamine-beta-hydroxylase. The plasma catecholamine concentrations reflected the different sites of action of the drugs in the sympathoadrenal system, i.e. guanethidine mainly reduced circulating norepinephrine and dopamine-beta-hydroxylase by more than 50%, whereas EMD 21192 decreased considerably by the total catecholamines (mainly epinephrine) without altering significantly in the plasma norepinephrine. Disappearance or reduction of fluorescent nerve endings in the iris and the heart and a decrease of the intensity of fluorescence in chromaffin cells of the adrenal gland caused by the drugs were consistent with the biochemical alteration. Whereas the repeated doses of guanethidine caused degeneration of sympathetic nerves, destruction of adrenergic neurons was not found after prolonged treatment with EMD 21192.

Biochemical and morphologic study of catecholamine metabolism in spontaneously hypertensive rats

Catecholamines and catecholamine-synthesizing enzymes have been studied quantitatively in specific brain areas of spontaneously (genetically) hypertensive rats by means of a combination of sensitive enzymatic-isotopic methods and a microdissecting technique. Changes in catecholamine metabolism were found to be localized to regions of the brain implicated in the regulation of blood pressure. Noradrenaline levels were decreased in specific nuclei of the anterior hypothalamus and in the nucleus interstitialis striae terminalis ventralis. The activity of the adrenaline-forming enzyme, phenyl-ethanolamine-N-methyl transferase, was increased in the A1 and A2 areas of the brain stem. These results implicate catecholamine-forming neurons in the hypothalamus and brain stem in the development of spontaneous hypertension in rats.

Peripheral and central catecholaminergic neurons in genetic and experimental hypertension in rats

1. Activity of peripheral and central catecholaminergic neurons was studied in spontaneously hypertensive rats (SHR) and deoxycorticosterone (DOCA)-salt hypertensive rats. 2. In young SHR (4 weeks) the plasma values of bpth noradrenaline and dopamine-beta-hydroxylase activity were increased compared with those of normotensive rats of the Wistar/Kyoto strain. Total catecholamines (mostly adrenaline) were not significantly different. 3. In the adrenal glands of 2-weeks-old and 4-weeks-old SHR activities of tyrosine hydroxylase, dopamine-beta-hydroxylase, phenylethanolamine-N-methyl transferase were decreased, compared to Wistar/Kyoto rats. 4. The adrenaline-forming enzyme was elevated in the A1 and A2 regions of the brain stem of 4-weeks-old SHR and in the A1 region of adult DOCA-salt hypertensive rats. 5. In the adrenal glands of adult DOCA-salt hypertensive rats tyrosine hydroxylase activity was increased. 6. These results implicate peripheral noradrenaline-containing neurons and central adrenaline-containing neurons in the development of genetic and experimental hypertension in rats.