Stereoselective disposition of racemic E-10-hydroxynortriptyline in human beings

The disposition and elimination kinetics of the enantiomers of E-10-hydroxynortriptyline (E-10-OH-NT) were studied in six rapid and four slow hydroxylators of debrisoquin after a single oral dose of 75 mg racemic E-10-OH-NT hydrogen maleate. The plasma levels and the AUC of unconjugated (-)E-10-OH-NT were two to five times higher than those of (+)E-10-OH-NT. The plasma half-lives of both enantiomers were 8 to 9 hours. A significantly higher proportion of the given dose of (+)E-10-OH-NT (64.4% +/- 12.1%) than of (-)E-10-OH-NT (35.3% +/- 9.7%) was recovered in urine as glucuronide conjugate, but more (-)E-10-OH-NT was recovered unchanged in urine. The total oral plasma clearance and the metabolic clearance by glucuronidation were significantly (p less than 0.0001) higher for (+)E-10-OH-NT than for (-)E-10-OH-NT. The findings indicate that first-pass glucuronidation of E-10-OH-NT is enantioselective in human beings in vivo, with preference for (+)E-10-OH-NT. The renal clearance of unbound (-)E-10-OH-NT (0.57 +/- 0.16 L.kg-1.hr-1), on the other hand, exceeded that of (+)E-10-OH-NT (0.44 +/- 0.14 L.kg-1.hr-1) (p less than 0.005), which suggests enantioselective tubular secretion. The debrisoquin hydroxylation status was not associated with any of the investigated kinetic processes that relate to E-10-OH-NT.     

Effect of cimetidine or ranitidine administration on nifedipine pharmacokinetics and pharmacodynamics

The effect of cimetidine or ranitidine administration on responses to single and multiple doses of nifedipine were studied in 11 subjects who received cimetidine (300 mg q.i.d.) and 12 who received ranitidine (150 mg b.i.d.) in combination with nifedipine. After single doses of nifedipine, cimetidine decreased apparent oral clearance (dose/AUC) from 66 +/- 32 L/hr to 33 +/- 14 L/hr (p less than 0.01); elimination half-life increased from 4.0 +/- 2.2 to 4.9 +/- 2.9 hours (p less than 0.07). Increases in heart rate were greater (26 +/- 13 vs 13 +/- 11 beats/min standing; 19 +/- 11 vs 9 +/- 9 beats/min supine) and lasted longer than after nifedipine alone. Hypotensive effects were similar (10 +/- 7 mm Hg decrease vs 9 +/- 9 mm Hg). During nifedipine multiple-dose administration, cimetidine decreased the apparent oral clearance from 76 +/- 39 to 43 +/- 20 L/hr (p less than 0.01). Blood pressure responses were not altered by cimetidine but heart rate increased more (18 +/- 9 vs 9 +/- 9 beats/min supine; 18 +/- 13 vs 13 +/- 14 beats/min standing). Ranitidine coadministration did not alter nifedipine elimination or dynamic responses. During administration of nifedipine alone, the ratio of oral clearances (multiple to single doses) was 1.1 +/- 0.5. Thus (1) cimetidine but not ranitidine alters responses to nifedipine and (2) nifedipine kinetics do not differ between single- vs multiple-dose conditions.     

Therapeutic drug monitoring of amitriptyline: impact of age, smoking and contraceptives on drug and metabolite levels in bulimic women

Concentrations of amitriptyline (AT), nortriptyline (NT) and E-10-hydroxynortriptyline (E-10-OH-NT) were measured in 18 women with bulimia receiving 100 mg AT/day for at least 6 wk. After onset of treatment between days 36 and 57 there is a decrease in AT and an increase in E-10-OH-NT concentrations, probably due to an autoinductive effect on hydroxylation. The estimated mean (+/- SD; range; n) elimination half-life time of AT was 14.0 (+/- 7.8 h; 7.5-38.5 h; 14). On day 36, AT concentrations in females using oral contraceptives (OC) were higher than in non-users of OC, which indicates inhibition of AT metabolism by OC. In all smokers the E-10-OH-NT concentrations on day 36 were lower than in non-smokers. Our findings suggest induction of N-demethylation and glucuronidation by smoke components.     

Nadolol antihypertensive effect and disposition in young and elderly adults with mild to moderate essential hypertension

Nadolol was effective and well tolerated as once-daily monotherapy for mild to moderate essential supine diastolic hypertension (SDBP) in 10 young (mean age, 39 years) and 12 elderly (mean age, 68 years) patients in a single-blind, placebo-baseline, escalating-dose study. Doses required to reduce SDBP to 90 mm Hg were not different in young (1.08 +/- 0.21 mg/kg/day) and elderly (0.82 +/- 0.14 mg/kg/day) patients (mean +/- SE). Trough plasma nadolol concentrations at steady state were similar and were linearly related to dose in both groups. More unchanged nadolol was recovered in 24-hour urine samples from young subjects (15.6% +/- 1.9%) than from elderly ones (10.7% +/- 1.1%) (p = 0.028). With increasing nadolol doses, plasma norepinephrine concentration increased and isoproterenol sensitivity decreased in both young and elderly subjects, and creatinine clearance and plasma active renin levels were unchanged; plasma inactive renin levels increased in the young, and aldosterone concentration declined in the elderly with the lowest nadolol dose.     

Analgesic and antidepressive effects of low-dose amitriptyline in relation to its metabolism in patients with chronic pain

The analgesic and antidepressive effects of amitriptyline (AT) in relation to its kinetics and metabolism were studied in 19 outpatients with chronic pain who received a daily dose of 75 mg AT for at least 6 weeks. Riboflavin was added to the medication to check compliance. On days 0, 4, and 8 and weeks 3, 6, 9, and 12 after the start of dosing, blood samples were drawn from the patients 10 +/- 1 hours after the first morning dose and a sample of the first morning urine was taken to check riboflavin. Serum levels of AT and its metabolites, especially nortriptyline (NT) and E-10-hydroxy-nortriptyline (E-10-OH-NT), were measured by HPLC. On day 0 and at 3, 6, and 12 weeks the severity of depression was scored by means of a self-rating depression scale and pain intensity scores were measured. In addition, after 6 weeks of dosing patients estimated their percentage of pain in comparison with baseline. Mean (+/- SD) steady-state concentrations of AT, NT, and E-10-OH-NT were 36 +/- 23.5, 28 +/- 14.9, and 52 +/- 23.7 micrograms/L, respectively, in male patients (n = 8; age 45 +/- 7.4 years) and 34 +/- 14.6, 45 +/- 25.1, and 40 +/- 15.6 micrograms/L, respectively, in female patients (n = 11; age 46 +/- 6.8 years). There was a significant sex-related difference in the NT/AT ratio, which was higher in women.(ABSTRACT TRUNCATED AT 250 WORDS)     

Little anticholinergic effect of E-10-hydroxynortriptyline compared with nortriptyline in healthy subjects

Six healthy male subjects were randomly given nortriptyline (NT) (25 and 50 mg) and placebo in a double-blind, crossover study. An NT dose of 50 mg (but not 25 mg) clearly reduced saliva flow (P less than 0.05) and was therefore used for comparison with the major and active metabolite of NT, E-10-hydroxynortriptyline (E-10-OH-NT). Equimolar doses of both compounds (and placebo) were randomly given to eight healthy male subjects in another double-blind, crossover study aimed to assess the reduction of saliva flow. NT significantly depressed saliva flow compared with both placebo (P less than 0.01) and E-10-OH-NT (P less than 0.05). By contrast, there was no difference between E-10-OH-NT and placebo. This study confirms previous indications that the anticholinergic effect of E-10-OH-NT is considerably less than that of the parent drug NT.     

Nortriptyline and debrisoquine hydroxylations in Ghanaian and Swedish subjects

Eleven Ghanaian and 12 Swedish subjects phenotyped with a debrisoquine (D) hydroxylation test were given a single oral dose of nortriptyline (NT). Much the same percentage of the given NT dose was excreted as 10-hydroxy-NT (10-OH-NT) by Ghanaians (43.1%) and Swedes (49.2%). There was a close correlation between plasma clearance of NT by 10-hydroxylation and the D metabolic ratio (D/4-OH-D in urine) in the Ghanaians (rs = -0.95; P less than 0.01) and Swedes (rs = -0.84; P less than 0.01). The E-isomer of 10-OH-NT is the major isomer in both Ghanaians (76% to 92% of total 10-OH-NT) and Swedes (78% to 95%). It is suggested that the E-10-hydroxylation of NT and the 4-hydroxylation of D are similarly coregulated in Ghanaians and Swedes.     

Relationship between infusion rates, plasma concentrations, and cardiovascular and metabolic effects during the infusion of norepinephrine in healthy volunteers.

OBJECTIVE: To determine the relationship between iv infusion rate, plasma concentrations, and hemodynamic and metabolic actions of norepinephrine. DESIGN: Norepinephrine was administered by using five iv infusion rates (0.01 to 0.2 micrograms/kg/min) for 30 mins each to eight volunteers, for the purpose of constructing cumulative plasma concentration-response curves. SETTING: Laboratory of the Department of Anesthesiology at a university hospital. MEASUREMENTS AND MAIN RESULTS: Systolic and diastolic BP, heart rate, and the plasma concentrations of norepinephrine, glucose, nonesterified fatty acids, and insulin were measured at the end of each infusion rate. During the highest infusion rate, plasma norepinephrine concentrations increased from 199 +/- 75 to 7475 +/- 1071 pg/mL (1.18 +/- 0.44 to 44.18 +/- 6.33 nmol/L). Typical hemodynamic responses, such as increases in BP and decreases in heart rate, were seen, while the plasma concentrations of glucose and nonesterified fatty acids increased from 92 +/- 10 to 132 +/- 17 mg/dL (5.1 +/- 0.6 to 7.3 +/- 0.9 mmol/L) and 11 +/- 4 to 34 +/- 6 mg/dL (0.11 +/- 0.04 to 0.34 +/- 0.06 g/L), respectively, during the 0.2 micrograms/kg/min infusion rate (p less than .05). Despite the increase in glucose concentration, insulin remained at baseline values. Metabolic and hemodynamic effects occurred at similar plasma concentrations throughout the study. CONCLUSIONS: Administration of norepinephrine showed no selective hemodynamic actions. The metabolic responses observed in this investigation were similar to those responses seen during increased endogenous sympathetic nervous system activity, such as stress, exercise, or trauma.     

Effects of desmethylimipramine on plasma norepinephrine, pulse, and blood pressure

We followed the effects of a tricyclic antidepressant selective for norepinephrine (NE) uptake inhibition, desmethylimipramine (DMI), on blood pressure, heart rate, and plasma NE level in healthy subjects. After a single oral dose of 100 mg DMI, supine systolic and diastolic blood pressure and supine and upright heart rate rose, and there was an increment in heart rate with standing. After long-term low doses of the drug (mean daily dosage 67.5 mg), the upright level and increment with standing in plasma NE also rose. Supine NE levels also rose after the long-term higher dose (mean daily dosage 125 mg). No differences in any measures were detected between the short- and the two long-term dose levels of DMI. Our findings suggest that NE uptake inhibition induces physiologic elevation of NE concentration in the sympathetic neuroeffector region. A similar effect at synapses in the CNS might be involved in the mechanism of antidepressant action.     

Kinetics of alpha-difluoromethylornithine: an irreversible inhibitor of ornithine decarboxylase

We gave alpha-difluoromethylornithine (DFMO), a selective, irreversible inhibitor of ornithine decarboxylase, to six health men in single intravenous doses of 5 and 10 mg/kg body weight and oral doses of 10 and 20 mg/kg. Plasma concentrations were monitored during the 24 hr after each dose. Urine was collected from 0 to 24 hr after drug and amount of unchanged drug excreted was determined. Peak plasma concentrations were reached within 6 hr after oral doses. The decay of the plasma concentrations followed first-order kinetics with a mean half-life (t 1/2) for all four doses studied of 199 +/- 6 min (+/- SD). Mean total body clearance (ClT) for the four doses was 1.20 +/- 0.06 ml . min-1 . kg-1. Mean renal clearance was determined as 0.99 +/- 0.03 ml . min-1 . kg-1, accounting for 83% of drug elimination. Mean apparent volume of distribution (aVD) was 0.337 +/- 0.031 l/kg-1, corresponding to 24 l for 70 kg of body weight. The amount of unchanged drug in 24-hr urine samples was 47 +/- 7% and 40 +/- 11% after 10 and 20 mg/kg orally, and 78% and 81 +/- 8% after 5 and 10 mg/kg intravenously. Bioavailability of the 10 mg/kg dose was estimated as 58% from the urinary recoveries and as 54% from the areas under the plasma concentration curves (AUC 0 leads to infinity). Since doubling of the dose resulted in a doubling of the mean AUC 0 leads to infinity and since other kinetic parameters, such as aVD, t 1/2, ClT, and the urinary recovery of unchanged drug, were essentially the same at all doses, DFMO kinetics follow a dose-linear model.     

Clinical and biochemical effects during treatment of depression with nortriptyline: the role of 10-hydroxynortriptyline

Plasma concentrations of nortriptyline (NT) and its major metabolite 10-hydroxy-NT (10-OH-NT) were measured in 30 patients with depression, treated with NT for 3 weeks. Nine patients who recovered completely had plasma concentrations of NT and 10-OH-NT ranging from 358 to 728 nmol/L and from 428 to 688 nmol/L, respectively. Of the 21 patients who did not recover completely, only four had plasma concentrations within the window limited by these two plasma concentration ranges. A correlation was found between the degree of amelioration and the plasma concentration of NT (rs = 0.469; P less than 0.01). Lumbar punctures were performed in 26 patients before and after 3 weeks of NT treatment. During treatment there was a 30.9% mean decrease in the noradrenaline metabolite 4-hydroxy-3-methoxyphenylglycol (HMPG) in cerebrospinal fluid (CSF). We could not evaluate the extent to which this decrease was caused by NT or 10-OH-NT, respectively, because both are strong inhibitors of noradrenaline uptake. The ratio between the concentration of NT and 10-OH-NT in CSF correlated to the reduction of HMPG in CSF (r = 0.397; P less than 0.05) and to the amelioration of depression (rs = 0.623; P less than 0.001). This might indicate that NT and 10-OH-NT interact on the noradrenaline system in a nonadditive way. During treatment there was a 15.2% decrease in CSF concentration of the serotonin metabolite 5-hydroxyindoleacetic acid. The reduction was significantly correlated to the CSF concentration of NT but not to that of 10-OH-NT. This is in accordance with the fact that NT is a more potent inhibitor of serotonin uptake than is 10-OH-NT. The dopamine metabolite homovanillic acid in CSF decreased significantly by 10.0%. The biochemical data indicate that noradrenergic, serotoninergic, and dopaminergic systems are affected by NT treatment and that 10-OH-NT might be more selective on noradrenergic neurons than the parent drug.     

Cerebrospinal fluid penetration and pharmacokinetics of levofloxacin in an experimental rabbit meningitis model

This study was designed to investigate the penetration across the blood-brain barrier of three doses of levofloxacin using a microdialysis probe implanted into the cerebrospinal fluid (CSF) of a rabbit pneumococcal meningitis model. The microdialysis guide cannula was implanted into rabbit subarachnoid space using a stereotaxic frame. After 3 days, 10(4) cfu Streptococcus pneumoniae serotype 3 in 0.3 mL saline was injected via intracisternal puncture and animals were allowed to incubate the organisms for 16-18 h. Groups of animals (n = 5) then received 7, 10.5 or 14 mg/kg iv of the drug over 10 min. Plasma samples were obtained via an ear vein 0, 0.25, 0.5, 0.75, 1, 2, 4, 6 and 8 h after the antibiotic infusion. CSF microdialysis effluent samples were collected every 0.5 h for the entire experiment. Plasma and microdialysis effluent samples were analysed by HPLC. AUC(0-8) in plasma and CSF were computed using the trapezoid rule. The elimination half-life in plasma and CSF was calculated using non-linear regression analysis. The unbound peak plasma concentrations for the three doses studied were 3.9, 6.4 and 10.3 mg/L, respectively. There was a significant increase in the plasma AUC(0-8) [29.7 +/- 6.3, 49.1 +/- 19.1 and 67.6 +/- 8.9 mg x h/L (P < 0.005)]. The unbound peak CSF concentrations were 3.8, 5.7 and 8.6 mg/L and occurred at 0-0.5 h after the administration of the dose. The AUC(CSF(0-8)) was significantly higher as the dose was increased (7 mg/kg, 15.8 +/- 6.6; 10.5 mg/kg, 37.3 +/- 7.8; and 14 mg/kg, 46.4 +/- 20.9 mg x h/L; P < 0.03). The penetration of levofloxacin averaged 53% for the 7 mg/kg dosage group, 76% for the 10.5 mg/kg group and 68% for the 14 mg/kg group. Our results demonstrate that levofloxacin penetration into the CSF averages 66% for the doses that would be used in clinical practice.     

Clinical pharmacologic observations on atenolol, a beta-adrenoceptor blocker.

The effects of oral and intravenous administration of atenolol were studied in healthy volunteers. The oral administration of a series of single doses of atenolol reduced an exercise tachycardia. After a 200-mg dose, the effect on an exercise tachycardia was maximal at 3 hr and declined linearly with time at a rate of approximately 10% per 24 hr. The peak plasma atenolol concentration occurred at 3 hr and thereafter declined exponentially with time with an elimination half-life of 6.36 +/- 0.55 hr: 43 +/- 3.9% of the dose was excreted in the urine within 72 hr. There was a correlation between the reduction in an exercise tachycardia and the logarithm of the corresponding plasma concentration. The intravenous administration of atenolol reduced exercise tachycardia with a significant correlation between effect and plasma concentration. After 50 mg intravenously, 100% of the dose was recovered from the urine, and the clearance was 97.3 ml/min. Comparison of AUC O leads to chi after oral and intravenous administration of 50 mg showed the bioavailability to be 63% after oral drug. Repeated oral administration of atenolol 200 mg daily either as a single dose or in divided 12 hourly doses for 8 days maintained reduction of an exercise tachycardia of at least 24% during the period of drug administration. The plasma elimination half-life, area under the plasma concentration-time curve, and peak plasma concentration after 200 mg atenolol were not changed by chronic dosing for 8 days.     

Evaluation of isradipine (PN 200-110) in mild to moderate hypertension

The efficacy and safety of isradipine (PN 200-110), a new dihydropyridine calcium antagonist, was evaluated in 87 hypertensive patients in a placebo-controlled, double-blind, randomized multicenter trial. After a 3-week single-blind washout phase, isradipine (or matching placebo) was administered for 4 weeks, beginning at 2.5 mg b.i.d. with increments of 2.5 mg b.i.d. at weekly intervals if supine diastolic blood pressure remained greater than or equal to 90 mm Hg. At the end of 1 week average supine blood pressure in the isradipine group (n = 45) fell from a baseline of 156 +/- 13/104 +/- 4 mm Hg to 146 +/- 14/97 +/- 7 mm Hg. By week 4 blood pressure was reduced by 19/14 mm Hg compared with 4/5 mm Hg in the placebo group (P less than 0.001 between groups). Supine and standing pulse rates were slightly increased initially with isradipine therapy but returned to baseline with increasing isradipine doses. Blood pressure responses at week 4 were good or excellent (supine diastolic less than or equal to 90 mm Hg or greater than or equal to 10 mm Hg decrease from baseline) in 87% of isradipine-treated patients and in 26% of placebo-treated patients. Headache, edema, abdominal discomfort, and constipation occurred slightly more frequently in isradipine-treated patients than in placebo-treated control subjects. The results indicate that isradipine, administered as monotherapy in doses of 2.5 to 10 mg b.i.d., is safe and effective in patients with mild to moderate essential hypertension.     

Clinical pharmacology of doxazosin in patients with essential hypertension

Doxazosin is a new quinazoline derivative that, like prazosin, has selectivity for alpha 1-receptors. A three-way crossover, randomized, open study in 18 patients with essential hypertension was conducted to investigate the clinical pharmacokinetics of 2, 4, and 8 mg doxazosin at steady state. The pharmacokinetics of the initial 2 mg dose was also studied. Doxazosin showed linear pharmacokinetics. Increases in doses from 2 to 8 mg (steady state) produced proportional increases in doxazosin serum levels (maximum plasma drug concentration [Cmax] minimum plasma drug concentration [C min], and O-24-hour area under the curve [AUC(p-24)], whereas half-life (t1/2) (19.4, 18.7, and 19.7 hours, respectively), volume of distribution (3.4, 3.4, and 3.6 L/kg, respectively), clearance from serum (2.2, 2.2, and 2.1 ml/min/kg, respectively), and degree of protein binding (1.2%, 1.0%, and 1.0% unbound, respectively) were dose independent. Similar t1/2 and time to reach peak concentration (tmax) were obtained with 2 mg initial dose and 2 mg steady state. alpha 1-Acid glycoprotein levels were unchanged during doxazosin treatment. Doxazosin lowered supine and standing systolic and diastolic blood pressure. The blood pressure reduction was associated with an increase in heart rate. Peak hypotensive and tachycardic effects occurred 5.7 +/- 0.1 hours after administration, whereas Cmax was achieved at 2.4 +/- 0.7 hours (tmax). Greater decreases in systolic blood pressure and increases in heart rate were seen in standing than in supine position. The reduction in standing systolic and diastolic blood pressure with 8 mg was greater than with 2 mg (P less than 0.05); however, the increases in heart rate were not different. Dizziness, headaches, and dry mouth were the most frequent side effects. This study indicates that doxazosin shows linear pharmacokinetics between 2 and 8 mg and that because of its long t1/2, once-a-day administration should be adequate for the treatment of hypertension.     

Nifedipine tablet vs. hydralazine in patients with persisting hypertension who receive combined diuretic and beta-blocker therapy

The antihypertensive effects of a 20 mg tablet of nifedipine were compared with those of hydralazine in a randomized, double-blind, placebo-controlled study. Nineteen patients with a diastolic blood pressure (BP) between 95 and 120 mm Hg despite combined diuretic and beta-blocker therapy completed the protocol. After 2 weeks of placebo each subject received increasing doses of nifedipine (20, 40, and 60 mg b.i.d.) and hydralazine (25, 50, and 100 mg b.i.d.) if tolerated or until goal BP (supine and standing diastolic BP less than 85 mm Hg) was achieved. Both nifedipine and hydralazine significantly lowered supine BP from placebo baseline (146 +/- 3/96 +/- 2 mm Hg) to 119 +/- 3/80 +/- 2 and 129 +/- 2/81 +/- 2 mm Hg, respectively. The decrease in systolic BP with nifedipine was significantly lower than that with hydralazine at 9 weeks. Neither drug significantly altered heart rate. Mean left ventricular ejection fractions were similar for nifedipine (67% +/- 2%), hydralazine (69% +/- 3%), and placebo (66% +/- 2%). The nifedipine tablet appears to be an effective antihypertensive agent in patients whose BP remains high despite combined diuretic and beta-blocker therapy.     

Hemodynamic effects of reboxetine in healthy male volunteers.

BACKGROUND: Reboxetine [(R,S)-2[(R,S)-alpha-(2-ethoxyphenoxy)benzyl]morpholine methanesulfonate] is a racemic compound that consists of equal proportions of R,R- and S,S-enantiomers. This study investigated the hemodynamic effects of reboxetine and the R,R-enantiomer compared with placebo in volunteers. The pharmacokinetics of reboxetine and its enantiomers were also investigated in the study. METHODS: Nine healthy, male volunteers received single doses of 4 mg reboxetine, 2 mg R,R-enantiomer, and placebo at weekly intervals. Reboxetine and the R,R-enantiomer were well tolerated in all volunteers. RESULTS: The heart rates of patients in the supine and standing positions were increased after reboxetine administration compared with the R,R-enantiomer (P < .05, except supine heart rate at 6 hours) and placebo (P < .05). Supine systolic and diastolic blood pressure was also increased by 3 +/- 4 and 1 +/- 4 mm Hg, respectively, after reboxetine compared with R,R-enantiomer (-2 +/- 4 and -4 +/- 3 mm Hg) and placebo (-4 +/- 4 and -4 +/- 4 mm Hg) administration. The systolic and diastolic blood pressure measurements for subjects while standing did not differ significantly among treatments. There was no significant difference between the maximum plasma concentration, mean time to maximum plasma concentration, plasma half-life, or area under the plasma concentration-time curve (AUC) of the R,R-enantiomer after reboxetine or R,R-enantiomer administration. The ratio of the mean AUC values for the R,R- and S,S-enantiomers was 2.1. CONCLUSION: These findings suggest that the S,S-enantiomer is responsible for the hemodynamic effects of reboxetine in humans. Increases in supine blood pressure after reboxetine administration may be interpreted as regression to the mean value and not caused by any treatment effect.     

Differences in lithium effects in depressed and healthy subjects

To evaluate the neurotransmitter actions of lithium without the confounding biochemical abnormalities associated with affective disorders, Li was given to 12 hospitalized healthy young men. After a 600-mg loading dose, subjects were placed on "therapeutic" Li doses averaging 1225 +/- 300 mg for 1 wk, reaching steady-state plasma levels of 0.82 +/- 0.17 mEq/l. Cardiovascular function at rest and diastolic blood pressure and pulse on standing were not altered by Li. Average baseline plasma norepinephrine (NE) concentration in the supine position (1.07 +/- 0.50 pmol/ml) did not change after 1 wk of Li dosing (1.16 +/- 0.57 pmol/ml). There was similar variability, without mean change, in plasma NE increments after orthostatic challenge and in plasma 3-methoxy-4-hydroxyphenylglycol concentrations before and during Li dosing. Urine volume was stable throughout the week of drug dosing, during which daily NE excretion was constant. In contrast to earlier data obtained in patients with depression receiving Li, there were no Li-related decrements in average whole-body NE or dopamine turnover. Mean daily urinary excretion rates of serotonin and its major metabolite 5-hydroxyindoleacetic acid did not change throughout the study. Our and other studies suggest that Li has a corrective action in patients with depression and hypothesized neurotransmitter abnormalities, but Li does not affect individuals without affective disorders.     

Effect of apolipoprotein E polymorphism on serum uric acid levels in healthy subjects.

BACKGROUND: We have previously shown that apolipoprotein E (apo E-) polymorphism may affect serum creatinine concentration and predicted glomerular filtration rate in healthy individuals. On the other hand, there are limited data regarding the possible influence of apo E- polymorphism on serum uric acid (SUA) levels. METHODS: Two hundred ninety (148 male, 142 female) apparently healthy white individuals were studied. apo E- genotypes, serum lipid parameters including apolipoproteins, insulin resistance using the homeostasis model assessment (HOMA) as a marker, serum and urine creatinine levels, and serum and urine uric acid concentration were determined in all participants. RESULTS: The apo E-2 allele was associated with lower serum levels of total cholesterol, higher levels of triglycerides and apo E-, and increased serum creatinine concentration compared with the apo E-3 and apo E-4 alleles in our population. Furthermore, the apo E-2 allele was associated with higher SUA levels (321.3+/-101.1 micrmol/L [5.4+/-1.7 mg/dL]) compared with the apo E-3 allele (261.8+/-89.2 micromol/L [4.4+/-1.5 mg/dL]; p= .012) and the apo E-4 allele (243.9+/-65.4 micromol/L [4.1+/-1.1 mg/dL]; p= .010), whereas the apo E-2 allele was associated with a nonsignificantdecrease in the fractional renal excretion of uric acid (FEUA) compared with the apo E-3 and apo E-4 alleles (7.9+/-2.2% vs 8.7+/-4.2% vs 8.9+/-5.1%, respectively; p = .53). These observations remained statistically significant when the effect of apo E- polymorphism on SUA levels was adjusted for gender, age, systolic and diastolic blood pressure, body mass index, serum creatinine, and triglyceride and apo E- levels, as well as for HOMA index and FEUA. CONCLUSIONS: Our data provide evidence, for the first time, that the apo E-2 allele is independently associated with increased SUA levels in healthy individuals.     

Kinetics and absolute bioavailability of atenolol.

Twelve healthy volunteers received four single doses of atenolol (25-, 50-, and 100-mg oral solutions and a 50-mg intravenous infusion), each dose separated by at least one week. Blood and urine assayed for atenolol by a high pressure liquid chromatography (HPLC) method. Kinetic analysis of the intravenous data indicates a three-compartment model with elimination from the central compartment. The mean (+/- SD) terminal elimination half-life is 6.06 +/- 2.02 hr, the mean volume of the central compartment is 0.173 L/kg, and 94.1 +/- 8.0% of the intravenous dose is excreted in the urine. The mean value of the plasma clearance is 10.7 +/- 1.27 L/hr and of the renal plasma clearance, 10.4 +/- 1.14 L/hr. The mean absolute bioavailability for the 25-, 50-, and 100-mg oral doses is 0.52 +/- 0.18, 0.54 +/- 0.12, and 0.58 +/- 0.16, respectively. The maximum plasma concentration varies as a linear function of dose. Time to mean maximum plasma concentration (3.0 hr) and the time for half of the bioavailable dose to be absorbed (2.0 hr) do not differ significantly with dose. The mean renal plasma clearance after oral doses (9.49 +/- 1.6 L/hr) is in the same range as renal clearance after intravenous doses.