Disposition of diazepam and its major metabolite desmethyldiazepam in patients with liver disease.

In six patients with cirrhosis and five patients with fibrosis of the liver elimination of diazepam (D) was compared after single and subchronic dosage. The pharmacokinetics of the major metabolite desmethyldiazepam (DD) was investigated in four healthy individuals and four patients with hepatic dysfunction and compared to its parent compound D. In the initial study, 11 patients with liver disease (cirrhosis and fibrosis) had a longer half-life (T 1/2(beta) of 99.2 +/- 23.2 hr after a single intravenous bolus of 0.1 mg/kg of D than to age-matched normal subjects (46.6 +/- 14.2). After subchronic treatment with 10 mg of D for 7 days T 1/2(beta) was prolonged only slightly (p = 0.043) in these patients (107.6 +/- 25.2 hr). Neither total plasma clearance (Cl) nor the apparent volume of distribution (VdSS or VdCl) showed significant changes. After intravenous injection of DD (0.1 mg/kg) plasma levels declined in the same biexponential manner as after D. The cross-over study in the four normal subjects demonstrated that DD was eliminated much more slowly than D. Whereas for D, T 1/2(beta) and Cl were 32.6 +/- 11.3 hr and 32.3 +/- 11.0 ml/min, respectively, the corresponding values for DD were 50.9 +/- 6.2 hr and 11.3 +/- 3.1 ml/min, respectively, the corresponding values for DD were 50.9 +/- 6.2 hr and 11.3 +/- 3.1 ml/min. The accumulation of DD after multiple dosage could be explained by the fact that it is formed faster from D than it is eliminated. In four patients with liver disease the elimination of D and the elimination of DD were altered. In these patients T 1/2(beta) for DD was prolonged (p = 0.015) to 108.2 +/- 40.3 hr. This prolongation was caused by a decrease in Cl of 4.6 +/- 1.1 ml/min, (p = 0.003) whereas Vd(Cl) did not change significantly. This indicates that at least two steps in diazepam metabolism are impaired in patients with liver disease.

Tyramine kinetics and pressor sensitivity during monoamine oxidase inhibition by selegiline.

The effect of the monoamine oxidase inhibitor selegiline on tyramine metabolism and intravenous and oral tyramine pressor sensitivity was studied in healthy subjects. After oral doses of tyramine, which caused systolic blood pressure to increase by 30 mm Hg, we determined plasma concentrations of p-hydroxyphenylacetic acid (HPAA) and of conjugated and unconjugated tyramine. When 20 mg/day of selegiline was administered, the AUCspec of HPAA decreased from 86% to 64% and the AUCspec of conjugated tyramine increased from 13% to 35% of the sum of total tyramine and HPAA. Pressor sensitivity was enhanced more with oral administration of tyramine than with intravenous administration of tyramine. After the drug was discontinued, initial values were reached within 4 days (one subject) and 2 weeks (two subjects). Fifty-five percent of the selegiline dose was eliminated in urine as amphetamine and methamphetamine. The findings support the assumption that selegiline does not selectively inhibit monoamine oxidase-B (MAO-B) when administered in doses of 20 mg/day and higher.

Monoamine oxidase inhibition by phenelzine and brofaromine in healthy volunteers.

The two monoamine oxidase (MAO) inhibitors phenelzine and brofaromine given for 2 to 3 weeks were compared in six volunteers. Blood pressure sensitivity to intravenous tyramine increased 2.6-fold during phenelzine (60 mg/day) and 4.8-fold during brofaromine, whereas sensitivity to oral tyramine increased more during phenelzine (15.7-fold vs 8.5-fold). After withdrawal of phenelzine, pressor sensitivity to oral tyramine returned to control values within 2 and for more than 8 weeks. Relative bioavailability of conjugated tyramine was elevated sixfold by brofaromine and 11.6-fold by phenelzine. Urinary elimination of tryptamine increased during phenelzine and brofaromine to 12.7-fold and threefold, respectively. 3-Methoxy-4-hydroxyphenylglycol (MHPG) and 3-methoxy-4-hydroxymandelic acid (VMA) excretion decreased during brofaromine significantly by 72% and 49%, respectively. The nonsignificant decrease of MHPG excretion and the increase of intravenous tyramine pressor sensitivity caused by phenelzine are significantly related. The data suggest that the selective reversible MAO-A inhibitor brofaromine has a larger therapeutic safety than phenelzine.

The beta-adrenoceptor-coupled adenylate cyclase system in rat C6 glioma cells. Deamplification by isoproterenol and oxaprotiline.

The beta-adrenoceptor-coupled adenylate cyclase system in rat C6 glioma cells displays many characteristics observed in brain tissue: using nonlinear regression analysis of agonist competition binding curves, we demonstrated that the bulk of beta-adrenoceptors show high nanomolar affinity for isoproterenol; like in brain tissue, Gpp(NH)p does not shift agonist competition binding curves to the right; and the agonist isoproterenol rapidly downregulates the number of beta-adrenoceptors and deamplifies the norepinephrine signal. However, unlike in brain tissue, where (-)-oxaprotiline fails to decrease the number of beta-adrenoceptors and to desensitize the cyclic adenosine monophosphate generating system, it desensitizes the beta-adrenoceptor-coupled adenylate cyclase system in C6 glioma cells. Determination of the relative steady-state levels of beta-adrenoceptor messenger ribonucleic acid (mRNA) by Northern blot analysis showed a twofold increase in the steady-state levels of the mRNA at 30 minutes following exposure to (-)-isoproterenol or (-)-oxaprotiline. At 48 hours, basal values of mRNA were observed at a time when beta-adrenoceptors were maximally decreased. Further experiments on transcriptional activation, and mRNA stability and translation will be required to unravel the complexity of agonist-dependent and agonist-independent regulation of beta-adrenoceptor density and function.

The 'serotonin/norepinephrine link' beyond the beta adrenoceptor.

C6 rat glioma cells were utilized as a model system to probe the 'serotonin/norepinephrine link' at the level of preproenkephalin (PPE) gene expression. The beta adrenoceptor mediated increase in PPE mRNA was attenuated by the selective beta 1 adrenoceptor antagonist metoprolol which blocked the isoproterenol induced cyclic AMP generation by 97%. The subtype nonspecific antagonist propranolol blocked both the isoproterenol induced increase in cyclic AMP and the increase in the PPE mRNA steady-state levels. Serotonin (5-HT) had no effect on the density of beta adrenoceptors or their down-regulation by isoproterenol and did not alter the PPE gene expression in the absence of the beta signal. However, 5-HT significantly deamplified the beta signal mediated enhancement of the PPE mRNA thus indicating that the aminergic link occurs beyond the beta adrenoceptor.

Interaction of alcohol and transdermally administered scopolamine.

In a placebo-controlled, randomized, double-blind cross-over study in 12 healthy volunteers the effect of acute alcohol intake during treatment with transdermally administered scopolamine (TTS-scopolamine) was investigated. One group of six subjects reached maximal blood alcohol concentrations (BAC) of 80 mg/dL and another group of six subjects a BAC of 130 mg/dL. There was no significant potentiation of alcohol effects on critical flicker fusion frequency by TTS-scopolamine. Sensorimotor function (choice reaction task) was also not significantly more influence by the combination. There was no effect of scopolamine on the elimination of alcohol. The urinary excretion of scopolamine was not influenced by oral intake of alcohol. TTS-scopolamine caused only minor side effects in a few volunteers, such as dry mouth (2 of 12) and blurred vision (1 of 12).

Dose-dependent down-regulation of beta-adrenoceptors by isoproterenol in rat C6 glioma cells.

Nano- and micromolar isoproterenol concentrations were compared by studying cyclic AMP, beta-adrenoceptor density and beta 1-adrenoceptor mRNA in rat C6 glioma cells. 1 microM isoproterenol significantly changed all parameters at 15-30 min. The beta 1-antagonist metoprolol attenuated the response. No effects of nanomolar isoproterenol on these early changes were observed, although the density of beta-adrenoceptors was significantly reduced beginning at 12 h. The results indicate a different process for beta-adrenoceptor desensitization in C6 cells following physiologically low agonist concentrations.

Effect of brofaromine and pargyline on human plasma melatonin concentrations.

1. Plasma melatonin was used to determine the influence of two monoamine oxidase inhibitor drugs in 11 normal subjects. 2. Acute oral administration of the selective reversible MAO-A inhibitor brofaromine but not of the - in low doses - selective MAO-B inhibitor pargyline increased daytime melatonin with large variations in onset, degree and duration. 3. Further investigation of this selective action on melatonin might help to better understand the action of the therapeutically effective antidepressive therapy with selective MAO-A inhibitors.

Tyramine potentiation during treatment with MAO inhibitors: brofaromine and moclobemide vs irreversible inhibitors.

Healthy ambulatory subjects were treated p.o. for 2 to 4 weeks with 6 different MAO inhibitors (MAOI). MAOI drugs were given to (n) subjects. Brofaromine (Brof): 100-150 mg/d (39); moclobemide (Mocl): 450 mg/d (8); clorgyline (Clor): 5, 10, 15 mg/d (5); selegiline (Sel): 5, 20 mg/d (7); phenelzine (Phen): 30, 45, 60 mg/d (6); tranylcypromine (TCP): 20 mg/d (12). Pressor responsiveness to oral tyramine (TYR) was assessed before, during, and after treatment. In unmedicated subjects (Cont), doses of TYR to raise systolic blood pressure by at least 30 mm Hg (PD30), ranged between 200 and 800 mg. During treatment with MAOIs, the PD30 decreased. The median effective doses (ED 50) of TYR were: Cont (n = 55): 437 mg; Sel, 20 mg/d: 96 mg; Mocl 450 mg/d: 63 mg; Brof: 100-150 mg/d: 44 mg; Phen, 60 mg/d: 33 mg; Clor, 10 mg/d: 43 mg; CP: 8 mg. Pressor responsiveness to oral TYR normalized within 3 d (Mocl), 8 d (Brof), and 30 d (TCP). After Phen, in 2 subjects the potentiation persisted for 2 and 4 weeks, in 4 volunteers for 8 and more weeks. After Clor, only one of 4 subjects reached 83% of his early pressor sensitivity within 15 weeks. The results suggest that the two reversible MAO-A inhibitors Mocl and Brof may lessen the liability to TYR-related hypertensive reactions.

Effect of the new selective COMT inhibitor CGP 28014 A on the formation of 3-O-methyldopa (3OMD) in plasma of healthy subjects.

CGP 28014 A is a specific inhibitor of catechol-O-methyl transferase (COMT). The effect on COMT was assessed with the levodopa test in 5 unmedicated subjects and after pretreatment with 200-600 mg CGP 28014 p.o. Plasma concentrations of DOPA, 3-O-methyldopa (3OMD), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid were measured. CGP 28014 A decreased 3OMD not dose-related by 67% (p less than 0.05). This, and an increase of DOPAC shows COMT inhibition by this compound in humans.

Clinical pharmacology of reversible monoamine oxidase-A inhibitors.

Traditional monoamine oxidase inhibitors (MAOIs) have long been associated with tyramine-related hypertension--the cheese effect. Despite their undoubted clinical efficacy, this problem has restricted their use. New, selective, and reversible MAO-A inhibitors--which act only on the A isoenzyme--appear not to have this effect. Our investigations of these drugs, exemplified by brofaromine, have shown a reduced and more rapidly reversed tyramine pressor sensitivity. Moreover, we were unable to detect any clinically significant food interaction, following ingestion of a quantity of cheese containing sufficient tyramine to increase systolic blood pressure by at least 30 mm Hg. These results confirm the improved safety of brofaromine, and other drugs in this class, when compared with classic MAOIs.

Intra-subject variability of platelet alpha 2-adrenoceptor binding sites in healthy volunteers.

The specific alpha 2-adrenoceptor binding (Bmax and KD) of (3H-methyl)yohimbine to intact platelets of healthy young volunteers was not significantly different in 7 males and 7 females. Its extent was not dependent on the menstrual cycle. The intraindividual variability was relatively high with means between 6% and 38% for Bmax and between 10% and 39% for KD, respectively. An intra-assay variation of 5.4 to 12.4% for Bmax and of 5.1 to 19.6% for KD contributed to this variability. Therefore, drug effects on platelet alpha 2-adrenoceptor binding in intraindividual cross-over studies are evidential only if the drug-induced changes exceed the intra-subject variability. This should be examined by at least 3 estimates of pre-drug values.

[Hypertensive crises with reversible inhibitors of monoamine oxidases? Results of tyramine interaction studies]. / Hypertensive Krisen unter reversiblen Hemmstoffen der Monoaminoxidase? Ergebnisse von Tyramin-Interaktionsstudien.

Healthy ambulatory subjects took 6 different MAO inhibitors (MAOIs) orally for 2 to 4 weeks. The new reversible MAO-A inhibitors brofaromine and moclobemide were compared with the irreversible MAOIs clorgyline, selegiline, phenelzine and tranylcypromine. Pressor responsiveness to oral tyramine was assessed before, during and after treatment. In unmedicated subjects, doses of tyramine to raise systolic blood pressure by at least 30 mmHg (PD30) ranged between 200 and 800 mg. During treatment with MAOIs, the PD30 decreased. The ratio of median effective doses (ED50) of tyramine (pre- vs post-treatment) was: selegiline 5, moclobemide 7, brofaromine 10, clorgyline 10, phenelzine 13 and tranylcypromine 55. Pressor responsiveness normalized within 8 days after stopping the reversible MAOIs and 30 days after tranylcypromine. The increased sensitivity after phenelzine persisted for longer than 8 weeks and after clorgyline for longer than 15 weeks. The results suggest that the two reversible MAO-A inhibitors moclobemide and brofaromine carry a much reduced liability to tyramine-related hypertensive reactions.