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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 63 (1985), S. 1205-1211 
    ISSN: 1432-1440
    Keywords: Rifampicin ; Rifampicin metabolites ; Multiple dose pharmacokinetics ; Enzyme induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the pharmacokinetics of rifampicin and its major metabolites, 25-desacetylrifampicin and 3-formylrifampicin, in two groups of six patients with active pulmonary tuberculosis, who received either multiple oral or intravenous rifampicin therapy in combination with intravenous isoniazid and ethambutol. Serum concentrations of rifampicin were each determined after a single oral and intravenous test dose of 600 mg rifampicin at the beginning and after 1 and 3 weeks of tuberculostatic treatment. Analysis of rifampicin and its metabolites was performed by high-pressure liquid chromatography. It was found that, due to autoinduction of its metabolizing hepatic enzymes, the systemic clearance of rifampicin increased from 5.69 to 9.03 l/h after 3 weeks of multiple dosing. The volume of distribution of the drug was constant over the period of this study. The bioavailability of the active, orally administered rifampicin decreased from 93% after the first single oral dose to 68% after 3 weeks of oral and intravenous rifampicin therapy. Relating to the increase in systemic (hepatic) clearance, a bioavailability no lower than 90% can be predicted. The reduction to 68% indicates that, in addition to an increase of hepatic metabolism, an induction of a prehepatic “first-pass” effect resulted from multiple rifampicin doses. Our study of rifampicin metabolites confirm that prehepatic metabolism was induced, since a higher metabolic ratio resulted after the oral doses than after the intravenous rifampicin test doses. A preabsorptive process can therefore be excluded as a cause of reduced bioavailability.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1440
    Keywords: Polymorphic drug oxidation ; Metoprolol ; Propafenone ; Diltiazem ; Sparteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A 47-year-old patient suffering from coronary artery disease was admitted to the CCU in shock with IIIo AV block, severe hypotension, and impairment of ventricular function. One week prior to admission a therapy with standard doses of metoprolol (100 mg t.i.d. and then 100 mg b.i.d.) had been initiated. Two days before admission diltiazem (60 mg b.i.d.) was prescribed in addition. Analyses of a blood sample revealed unusually high plasma concentrations of metoprolol (〉 3000 ng/ml) and diltiazem (526 ng/ml). The patient recovered within 1 week following discontinuation of antianginal therapy. Three months later the patient was exposed to a single dose of metoprolol, diltiazem, propafenone (since he had received this drug in the past), and sparteine (as a probe for the debrisoquine/sparteine type polymorphism of oxidative drug metabolism). It was found that he was a poor metabolizer of all four drugs, indicating that their metabolism is under the same genetic control. Therefore, patients belonging to the poor-metabolizer phenotype of sparteine/debrisoquine polymorphism in drug metabolism, which constitutes 6.4% of the German population, may experience adverse drug reactions when treated with standard doses of one of these drugs alone. Moreover, the coadministration of these frequently used drugs is expected to be especially harmful in this subgroup of patients.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1440
    Keywords: Isoniazid ; Rifampicin ; Antituberculous agents ; Toxic Hepatitis ; Acetylator Phenotype ; Isoniazid-Rifampicin ; Tuberkulostatische Kombinationstherapie ; Toxische Hepatitis ; Acetyliererphänotyp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 95 Patienten mit aktiver Tbc untersuchten wir prospektive den Einfluß des Acetyliererphänotyps auf die hepatotoxische Nebenwirkung der tuberkulostatischen Kombination Isoniazid (INH) 10 mg/kg, Rifampicin (RMP) 10 mg/kg, Myambutol (EMB) 25 mg/kg. Neben einer viel höheren Inzidenz der Isoniazidhepatitis (SGOT, SGPT 〉 200 U/l) von 12,6% der Behandelten — verglichen zur Häufigkeit der Isoniazidhepatitis während Chemoprophylaxe mit Isoniazid als Monotherapie von 0,5–1% (IUAT 1969, U.S.P.H.S. 1971) — stellten wir bei der Kombinationstherapie ein signifikant höheres Risiko schwerer INH-induzierter Leberschädigungen bei Langsamacetylierern fest (p 〈 0,01): von 56 Langsamacetylierern entwickelten 26 (=46,4%) Transaminasenerhöhungen 〉 50 U/l, von 30 Schnellacetylierern dagegen nur 4 (=13,3%). Unter den 12 Patienten mit Isoniazidhepatitis befanden sichnur Langsamacetylierer. Frauen waren von der Isoniazidhepatitis häufiger betroffen als Männer (p 〈 0,05). Bei der Isoniazidhepatitis wurde entweder die Therapie vorübergehend abgesetzt oder als Zweierkombination RMP, EMB fortgesetzt. Bei leichterem Verlauf der Leberschädigung wurde die Therapie unverändert fortgesetzt. In allen Fällen normalisierten sich die Transaminasen innerhalb 2–4 Wochen. Die anschließende Wiederaufnahme der Dreifachtherapie ohne Dosisreduktion führte zu keinem erneuten Transaminasenanstieg. Das konstante Auftreten der INH-Hepatitis in der 2.–4. Woche (19±7 Tage) sowie die ohne Reaktion vertragene spätere Reexposition der vollen Dreifachtherapie sprechen für eine zeitlich begrenzte Interaktion des Rifampicin mit dem Isoniazid-Metabolismus in der Anfangsphase der tuberkulostatischen Therapie.
    Notes: Summary In 95 patients with active tuberculosis, we investigated in a prospective study the influence of the acetylator phenotype on the hepatotoxic side effects of the antituberculous regimen isoniazid (INH) 10 mg/kg, rifampicin (RMP) 10 mg/kg, and ethambutol (EMB) 25 mg/kg. Besides a much higher incidence of isoniazid hepatitis (SGOT, SGPT 〉 200 U/l) in 12.6% of patients treated — as compared to the incidence reported in large chemoprophylaxis trials with isoniazid monotherapy in the range of 0.5%–1% (IUAT 1969, U.S.P.H.S. 1971) — we observed a significant, higher risk of isoniazid-induced hepatotoxicity in slow acetylators (p 〈 0.01): in 26 of 56 slow acetylators (=46.4%), but only in 4 of 30 rapid acetylators (=13.3%) were transaminases in the serum elevated 〉 50 U/l. The 12 patients with the most severe hepatotoxic side effects (SGOT, SGPT 〉 200 U/l) were all slow acetylators. Women developed severe hepatic injury more often than men (p 〈 0.05). In cases with isoniazid hepatitis, triple therapy was either stopped or reduced to a combination RMP, EMB. In cases with less severe liver injury, triple therapy was continued. In all patients transaminases normalized within 2–4 weeks. On return to full triple therapy, none of the patients developed new elevation of transaminases. The constant occurrence of isoniazid hepatitis during the 2nd–4th week (19±7 days) as well as the normalization without any new hepatotoxic reaction suggest that there may be an interaction between RMP and isoniazid metabolism limited to the early phase of chemotherapy.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 63 (1985), S. 1180-1186 
    ISSN: 1432-1440
    Keywords: N-propylajmaline ; Pharmacokinetics ; Genetic polymorphism ; Sparteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to determine whether the metabolism of the antiarrhythmic drug N-propylajmaline is under the same genetic control as sparteine metabolism, the pharmacokinetics of this antiarrhythmic drug were studied in a group of six extensive and four poor metabolizers of sparteine. Pronounced differences in terminal half-life, total plasma clearance, metabolic clearance and urinary excretion of N-propylajmaline were observed between extensive and poor metabolizers. A close relationship between the total clearance and metabolic clearance of N-propylajmaline and sparteine could be demonstrated. Clinically available N-propylajmaline is a 55% to 45% mixture of thei-andn-diastereomers. The extensive metabolizers exhibited stereoselective metabolism; thei-diastereomer was preferentially metabolized. Poor metabolizers were characterized by a loss of this stereoselective metabolism. Five subjects were treated for 7 days with a daily N-propylajmaline dosage of either 60 mg or 20 mg. Since a close relationship between the clearance of N-propylajmaline and the metabolic ratio of sparteine had been observed after single dosing the metabolic ratio of sparteine was used to predict N-propylajmaline steady-state plasma concentrations during multiple dosing. Only in two extensive metabolizers with a metabolic ratio 〈0.4 predicted and observed, steady-state plasma concentrations were in good agreement. In the other three subjects observed steady-state plasma concentrations were appreciably higher than predicted. In these three subjects metabolic N-propylajmaline clearance decreased indicating saturation of N-propylajmaline metabolism during multiple dosing. The data indicate that N-propylajmaline metabolism is subject to a genetic polymorphism controlled by the sparteine/debrisoquine gene locus.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 46 (1968), S. 93-97 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In two normal subjects and ten patients the gastric secretory response to pentagastrin has been determinated. Pentagastrin is a synthetic polypeptide with an aminoacid sequence equal to that of the biologically active component of human gastrin. After intravenous application, a dose responcee relationship has been established between pentagastrin and gastric acid secretion over a range of 0,6 to 6,0γ/kg/hr of the polypeptide. As anticipated, both electrolyte composition and secretory volume change depending on the acid concentration. Subcutanously administered pentagastrin stimulated acid secretion with a correlation to time similar to that after histamine injection. The acid secretory capacity of pentagastrin reaches an average of 89% of that of 1.5 mg/kg of histolog showing, in single cases, a different relation to the histolog response. Only negligible side effects, as nausea and vomiting, have been observed after intravenous injection of pentagastrin. When pentagastrin was given subcutanously side effects, were more pronounced in a few cases, but temporary.
    Notes: Zusammenfassung Die Einwirkung von Pentagastrin, einem Pentapeptid, welches aus der biologisch wirksamen Aminosäuresequenz des menschlichen Gastrins besteht, auf die Magensaftsekretion wurde bei 2 Normalpersonen und 10 Patienten untersucht. Bei intravenöser Verabreichung besteht in einem Bereich von 6,0–0,6γ/kg/h eine Dosis-Wirkungs-Beziehung zwischen Pentagastrin und Säuresekretion. Die Elektrolytzusammensetzung des Magensaftes und das Sekretionsvolumen verändern sich erwartungsgemäß in Abhängigkeit von der Säurekonzentration. Pentagastrin subcutan verabreicht, verursacht eine Säuresekretion, deren zeitlicher Ablauf der Säuresekretion nach Histamin ähnlich ist. Die Säuresekretionsleistung nach Pentagastrin beträgt im Durchschnitt 89% der Säuresekretion nach subcutaner Belastung mit 1,5 mg je Kilogramm Histalog, zu der sie in Einzelfällen größere Unterschiede aufweist. Die Nebenwirkungen in Form von Übelkeit und Brechreiz waren bei intravenöser Verabreichung nur in Einzelfällen stärker und klangen rasch ab.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1440
    Keywords: Verapamil i.v. ; oral ; Plasmaspiegel ; Δ PQ ; Konzentrationswirkungsbeziehung ; Verapamil i.v. ; oral ; Plasma levels ; Δ PR ; Differences concentration-response curve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A close relationship between verapamil plasma concentration and effect on P–R interval could be established both after single i.v. and oral administration and during chronic oral treatment. After i.v. administration a linear relationship between verapamil plasma concentration and Δ P–R (y=x (0.74)+1.8) with a small between subject variation in the slope of the regression (%coefficient of variation 18.7, range 0.71–1.10) was observed. The slope of the oral plasma concentration response regression (y=x (0.33)−3.0) was statistically significantly (p〈0.05) less than the slope of the i.v. plasma level response regression. Interindividual variation in the slope was most pronounced (range 0.13 to 0.47). On average two to three times higher verapamil plasma levels were required after oral administration in order to produce the same increase in Δ PR as after intravenous administration. The most plausible explanation for the different slopes of the plasma level response regression seems to be stereo-selective presystemic elimination. Since after oral administration the plasma level response curve is less steep than after i.v. administration this indicates that the more active l-isomer is preferentially metabolized during hepatic first-pass metabolism.
    Notes: Zusammenfassung Sowohl nach intravenöser und oraler Einzelgabe als auch während chronischer oraler Behandlung mit Verapamil ließ sich eine signifikante Beziehung zwischen Verapamil-Plasmakonzentration und der Wirkung auf die PQ-Zeit feststellen. Nach intravenöser Verabreichung fand sich eine lineare Beziehung zwischen Verapamil-Plasmaspiegel und Δ PQ (y=x (0,74) + 1,8), wobei die Variation der Steilheit der Konzentrationswirkungsbeziehung nur geringe interindividuelle Unterschiede aufwies. (Variationscoeffizient 18,7%; 0,71–1,10). Die Steilheit der nach oraler Gabe beobachteten Plasmakonzentrationswirkungsbeziehung (y=x (0,33)−3,0) unterschied sich statistisch signifikant (p〈0,05) von der Steilheit der intravenösen Konzentrationswirkungsbeziehung. Erhebliche interindividuelle Schwankungen in der Steilheit dieser Konzentrationswirkungsbeziehung wurden nach oraler Gabe beobachtet (Bereich 0,13–0,47). Im Mittel waren nach oraler Gabe 2–3mal höhere Verapamil-Plasmaspiegel notwendig, um die gleiche Zunahme der PQ-Zeit wie nach intravenöser Applikation zu erzielen. Die plausibelste Erklärung für diese Unterschiede in der Steilheit der Plasmakonzentrations-wirkungsbeziehung dürfte in einem stereo-selektiven Firstpass Metabolismus nach oraler Gabe zu suchen sein. Da nach oraler Applikation die Steilheit der Plasmaspiegelwirkungsbeziehung wesentlich flacher als nach intravenöser Applikation verläuft, muß man annehmen, daß das pharmakologisch wesentlich wirksamere L-Isomer einen wesentlich stärkeren First-Pass Metabolismus als das D-Isomer unterliegt.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 62 (1984), S. 394-398 
    ISSN: 1432-1440
    Keywords: Gentamicin serum concentration ; Intratracheal administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In artificially ventilated patients, intratracheal aminoglycoside administration is used as a form of prophylaxis of broncho-pulmonary infections. In artificially ventilated patients with multiple organ failure, serum gentamicin concentrations were measured dependent on renal function after endotracheal administration. A standard commercial ampule of 40 mg gentamicin in a 1 ml solution was injected in undiluted form, intratracheally through the tubus, every 6 h. In the patients without renal failure, values over 1 µg/ml were only found in certain individual cases and reached a maximum of 1.5 µg/ml. In patients with renal failure even after prolonged application, the average serum concentrations were between 2 and 3.5 µg/ml. In a very few cases, however, levels of up to 10.5 µg/ml were measured. The daily serum pattern revealed a distinct dependence on the administration; 1 h after administration there was an increase in the serum concentrations which decreased to the initial levels after 6 h. When patients with renal impairment are given an aminoglycoside intratracheally, serum levels of up to 10.5 µg/ml may be reached and thus additional systemic aminoglycoside therapy should be avoided.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 42 (1978), S. 223-223 
    ISSN: 1432-0738
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 8 (1975), S. 33-39 
    ISSN: 1432-1041
    Keywords: m-octopamine ; metabolism ; first-pass effect ; man ; enteric absorption ; monohydroxylated phenylalkylamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The diminished sympathomimetic pressor activity of monohydroxylated phenylalkylamines after oral administration has been attributed to incomplete enteric absorption. Therefore, urinary excretion of the unchanged drug and its metabolites has been compared after intravenous and oral administration of3H-m-octopamine to eight patients. Identical amounts of3H-activity (80% of the dose) were excreted after the two routes of dosing, so enteric absorption has been assumed to be complete. Significant differences were found in the fraction of free urinarym-octopamine, which amounted to 10.5% of the dose after infusion and 0.58% after oral administration. The only metabolic pathways form-octopamine are deamination and conjugation. Following oral administration the percentage of conjugates was considerably higher than after intravenous infusion. This metabolic pattern appears typical of all phenylalkylamines with a hydroxyl group in themeta position. Ring hydroxylation to catecholamines was not observed. The enzymes mainly responsible for conjugation after oral administration are located in the gut wall. The resulting “first pass effect”, i.e. metabolism prior to the access to the central compartment, can account for the diminished pharmacodynamic effect after dosing by this route.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 8 (1975), S. 337-341 
    ISSN: 1432-1041
    Keywords: Carbamazepine ; carbamamazepine-10,11-epoxide ; pharmacokinetics ; induction of metabolism ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Carbamazepine (Tegretol®) was administered orally to four patients as a single dose, and one week later three times daily for 15–21 days. The plasma half-lives of the drug were shorter in all patients after multiple doses (20.9±5.0 hours) than after the initial single dose (35.6±15.3 hours). During multiple doses the plasma concentrations of the metabolite carbamazepine-10,11-epoxide followed those of the parent drug. The steady-state plasma concentrations expected during multiple doses were calculated from the pharmacokinetic parameters obtained in the single dose studies. The calculated levels were higher (17.2±7.2 µg/ml) than the observed maximal concentrations (8.4±1.6 µg/ml on day 4), which were obtained 3–4 days after starting the multiple doses. The levels tended to decrease further during the experimental period. The results suggest that carbamazepine induces its own metabolism in man.
    Type of Medium: Electronic Resource
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