H. Grobecker

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.

Cyclo-oxygenase-2 inhibition increases blood pressure in rats.

It is known that nonselective cyclo‐oxygenase (COX) inhibitors have small but significant effects on blood pressure (BP), most notably in hypertensive patients on antihypertensive medication. Whether selective COX‐2 inhibitors also interfere with BP regulation is not well understood. Therefore, we aimed to examine the effect of chronic treatment with a selective COX‐2 inhibitor (rofecoxib) on systolic blood pressure (sBP) in normotensive Wistar‐Kyoto rats (WKY) and on the developmental changes of sBP in young spontaneously hypertensive rats (SHR). In addition, we investigated a possible influence of salt intake on the effects of COX‐2 inhibition on BP in these two rat strains. Rofecoxib dose dependently increased sBP and decreased plasma levels of 6‐keto prostaglandin (PG)F1α in WKY rats fed a normal salt diet (0.6% NaCl, wt wt−1), without affecting serum thromboxane (TX)B2 levels. Rofecoxib significantly elevated sBP in both rat strains fed normal salt or high salt diet (8% NaCl, wt wt−1), but not in rats on low salt intake (0.02% NaCl, wt wt−1). Rofecoxib significantly decreased plasma levels of 6‐keto PGF1α in both rat strains fed normal or high salt diet, but not in rats during low salt intake. Rofecoxib exerted no influence on the changes of body weight nor on water intake. Plasma renin activity (PRA) and renocortical renin mRNA abundance were not changed by rofecoxib, but plasma aldosterone concentration (PAC) was significantly reduced. These results suggest that chronic inhibition of COX‐2 causes an increase of blood pressure that depends on prostacyclin synthesis. Furthermore, this increase is independent on genetic predisposition and can be prevented by salt deprivation. Since water intake and body weight gain were not changed by rofecoxib, fluid retention appears not to be a major reason for the development of hypertension. Similarly, an activation of the renin‐angiotensin‐aldosterone axis appears to be an unlikely candidate mechanism.

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

SummaryIn 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.ZusammenfassungZwölf gesunde freiwillige Probanden erhielten in einer offenen, randomisierten Cross-Over-Studie zweimal 250 mg Clarithromycin täglich und einmal 500 mg täglich. Am ersten und fünften Tag der Therapie wurden die pharmakokinetischen Parameter von Clarithromycin und seinem aktiven Metaboliten, 14-Hydroxy-Clarithromycin, in Serum, Speichel und Blutzellen (polymorphkernige Leukozyten (PMNs) und mononukleären Zellen (MNCs; nur Clarithromycin) bestimmt. Die mittleren Maximalkonzentrationen von Clarithromycin an Tag fünf waren nach 500 mg Clarithromycin einmal täglich mindestens doppelt so hoch wie nach 250 mg zweimal täglich (Serum: 2,3 vs. 1,2 mg/l; Speichel: 1,1 vs. 0,3 mg/l; MNCs 60 vs. 26 mg/l; PMNs 29 vs. 14 mg/l), die Talspiegel hingegen waren deutlich niedriger (Serum: 0,09 vs. 0,28 mg/l; Speichel: 0,06 vs. 0,13 mg/l; MNCs: <1 vs. 6,8 mg/l; PMNs: 0,8 vs. 2,8 mg/l). Die mittleren, relativen Serumkonzentrationen des aktiven Metaboliten, 14-Hydroxy-Clarithromycin, waren hingegen niedriger nach 500 mg Clarithromycin vs. 250 mg (0,78 vs. 0,46 mg/l). Die mittleren Maximalkonzentrationen in Speichel betrugen bei Clarithromycin 25–40% und bei Hydroxy-Clarithromycin 50–80% der maximalen Serumkonzentrationen. Clarithromycin zeigt eine gute und schnelle Diffusion in intrazelluläre und extrazelluläre Körperkompartimente. Im Hinblick auf Bioverfügbarkeit und Maximalkonzentrationen kann das Therapieschema von 500 mg einmal täglich gut mit dem Schema zweimal 250 mg täglich konkurrieren, die Talspiegel am Ende des 24-Stunden-Dosierungsintervalls sind jedoch niedriger.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. Zwölf gesunde freiwillige Probanden erhielten in einer offenen, randomisierten Cross-Over-Studie zweimal 250 mg Clarithromycin täglich und einmal 500 mg täglich. Am ersten und fünften Tag der Therapie wurden die pharmakokinetischen Parameter von Clarithromycin und seinem aktiven Metaboliten, 14-Hydroxy-Clarithromycin, in Serum, Speichel und Blutzellen (polymorphkernige Leukozyten (PMNs) und mononukleären Zellen (MNCs; nur Clarithromycin) bestimmt. Die mittleren Maximalkonzentrationen von Clarithromycin an Tag fünf waren nach 500 mg Clarithromycin einmal täglich mindestens doppelt so hoch wie nach 250 mg zweimal täglich (Serum: 2,3 vs. 1,2 mg/l; Speichel: 1,1 vs. 0,3 mg/l; MNCs 60 vs. 26 mg/l; PMNs 29 vs. 14 mg/l), die Talspiegel hingegen waren deutlich niedriger (Serum: 0,09 vs. 0,28 mg/l; Speichel: 0,06 vs. 0,13 mg/l; MNCs: <1 vs. 6,8 mg/l; PMNs: 0,8 vs. 2,8 mg/l). Die mittleren, relativen Serumkonzentrationen des aktiven Metaboliten, 14-Hydroxy-Clarithromycin, waren hingegen niedriger nach 500 mg Clarithromycin vs. 250 mg (0,78 vs. 0,46 mg/l). Die mittleren Maximalkonzentrationen in Speichel betrugen bei Clarithromycin 25–40% und bei Hydroxy-Clarithromycin 50–80% der maximalen Serumkonzentrationen. Clarithromycin zeigt eine gute und schnelle Diffusion in intrazelluläre und extrazelluläre Körperkompartimente. Im Hinblick auf Bioverfügbarkeit und Maximalkonzentrationen kann das Therapieschema von 500 mg einmal täglich gut mit dem Schema zweimal 250 mg täglich konkurrieren, die Talspiegel am Ende des 24-Stunden-Dosierungsintervalls sind jedoch niedriger.

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.

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.

Cefotaxime and desacetyl cefotaxime in human bile

SummaryTen patients were injected with 2 g cefotaxime i. v. The antibacterial activity in the bile was measured by the agar diffusion test and the concentrations of cefotaxime and desacetyl cefotaxime were determined by high performance liquid chromatography. The values found allow the use of cefotaxime in infectious biliary diseases.ZusammenfassungZehn Patienten wurden je 2 g Cefotaxim i. v. injiziert. In der Galleflüssigkeit wurden die antibakterielle Aktivität mittels Agardiffusionstest und die Konzentrationen von Cefotaxim und Desacetyl-Cefotaxim mit Hochdruckflüssigkeitschromatographie bestimmt, Die gefundenen Werte erlauben den Einsatz von Cefotaxim bei infektiösen Gallenwegserkrankungen.

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 ketanserin on hemodynamics, plasma-catecholamine concentrations, and serotonin uptake by platelets in volunteers and patients with congestive heart failure

Ketanserin, which preferentially blocks 5-HT2-serotonergic receptors, was injected intravenously (i.v.) to patients with congestive heart failure in a bolus dose of 10 mg, followed by an i.v. infusion of 3 mg/h over a period of 4 h. The drug caused a decrease in total peripheral resistance and, conversely, an increase in stroke volume. Right atrial and pulmonary artery pressures were decreased. Plasma noradrenaline rose twofold over the basal levels shortly after injection, but showed a distinct fall 2 h after beginning of the treatment. The concentrations of ketanserin in plasma after bolus injection approximated 100-150 ng/ml. The sympathoneuronal and sympathoadrenal reaction during tilting were increased after i.v. injection of 10 mg ketanserin in volunteers. The noradrenaline and adrenaline levels in plasma rose significantly more when compared with values before the injection of the drug. In vitro as well as in vivo ketanserin exerts a concentration-dependent inhibitory effect on the active transport of serotonin and catecholamines (dopamine, noradrenaline, adrenaline) into human platelets. Considering platelets as a model of the sympathetic neurons, the inhibition of reuptake of catecholamines by ketanserin could contribute to the observed increase in circulating catecholamines after injection of the drug.

Effect of three different doses of urapidil on blood glucose concentrations in the streptozotocin diabetic rat.

BACKGROUND AND OBJECTIVE Diabetes mellitus associated with hypertension often causes perioperative complications. The alpha1-adrenoceptor antagonist/5-hydroxytryptamine-1A receptor agonist urapidil is an approved drug used in hypertension and hypertensive emergencies. 5-Hydroxytryptamine-1A (5-HT1A) receptor agonists impair glucose metabolism. To evaluate a possible dose-dependent hyperglycaemic effect of urapidil due to its 5-HT1A receptor agonistic properties, the effect of three doses of urapidil on hyperglycaemia in the streptozotocin diabetic rat was investigated. METHODS Male Wistar-Kyoto rats were made diabetic by streptozotocin and randomly allocated to the following daily treatments for 7 days (n = 6 each): urapidil 6 mg kg(-1), urapidil 20 mg kg(-1), urapidil 60 mg kg(-1), insulin 4 IU kg(-1) subcutaneously. One diabetic group and one non-diabetic healthy group served as controls. RESULTS Treatment for 7 days with urapidil 20 mg kg(-1) and urapidil 60 mg kg(-1) reduced mean glucose concentrations significantly (urapidil-20: 15.6 +/- 1.1 mmol L(-1), P = 0.023; urapidil-60: 15.8 +/- 0.8 mmol L(-1), P = 0.04) compared with diabetic controls (20.9 +/- 0.8 mmol L(-1)), whereas those after urapidil 6 mg kg(-1) were similar to diabetic controls. Insulin treatment normalized blood glucose concentrations. CONCLUSIONS The alpha1-adrenoceptor antagonist/5-HT1A receptor agonist urapidil has no hyperglycaemic effect on experimental diabetes mellitus, even in high doses, despite its 5-HT1A receptor agonistic properties.

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

Summary1.We determined the number ofβ-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/mgβ-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 withl-practolol,dl-atenolol, and ICI 118,551 were performed and we calculated by a computer program in the whole spinal cord the following ratio ofβ-receptor subtypes: 80 ± 5%β1-receptors and 20 ± 5%β2-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.