Tolerability, pharmacokinetics and concentration-dependent hemodynamic effects of oral CF101, an A3 adenosine receptor agonist, in healthy young men

OBJECTIVES

To assess safety, tolerability, pharmacokinetics and hemodynamic effects of oral CF 101, an A3 adenosine receptor (A3AR) agonist, in healthy men.

METHODS

One single and 1 repeated dose, parallel-group, ascending dose, double-blind and placebo-controlled study in normal volunteers. In the single dose study, n = 15 subjects received 1, 5 or 10 mg oral CF101; in each group 1 subject received placebo, the remainder active CF101. In the repeat-dose study, n = 28 subjects received repeated 12-hourly oral doses of CF 101 (2, 3, 4 or 5 mg) for 7 days, in each group 2 subjects received placebo, the remainder active CF101. TEST MATERIALS: Single-dose study: CF101 in 30% Cremophor RH40. Multiple-dose sudy: CF101 in 0.5% methylcellulose suspension. Both studies: the corresponding vehicles were used as placebos. Galenicals were prepared remotely from the clinical study site to ensure double-blind nature of the study. RESULTS TOLERABILITY: Single doses up to 5 mg CF101 were safe and well-tolerated. However, the single dose of 10 mg CF101 was associated with flushing, tachycardia, nausea and vomiting, which were viewed as dose-limiting in normal volunteers. Single doses of CF101 (as well as the first of the multiple doses) were associated with increases in heart rate (8 - 24 beats/min after 5 mg and 18 - 55 beats/min after 10 mg). Multiple doses up to 4 mg 12-hourly for 7 days were safe and well-tolerated. However, the 5 mg multiple-dose group reported headache, drowsiness, hot flushes and dizziness on standing; this declined with dosing duration and was not dose-limiting in this study. Adverse events were commonest near t(max). RESULTS PHARMACOKINETICS: For oral CF101, the t(max) was always 1 - 2 h post-dose and t 1/2 about 9 h, in both the single- and multiple-dose studies. For a single 5 mg dose (mean +/- SD) C(max) = 81.6 +/- 23.6 ng/ml in the single dose study, and 63.6 +/- 22.0 ng/ml after the first of the multiple doses; AUC if was 904.0 +/- 221.9 ng.h/ml and 596.1 +/- 196.6 ng.h/ml for the 2 studies, respectively. After 7 days of multiple dosing there was little change, and AUC(0-24h) = 601.0 +/- 163.6 ng.h/ml. These pharmacokinetic parameters were linearly proportional to dose in the other treatment groups. RESULTS PHARMACODYNAMICS: Increases in heart rate were related to plasma concentration and evident only in the upper range of concentrations observed. There were no changes on ECG monitoring beyond sinus tachycardia, and, in particular, no evidence of PR prolongation in any subject (n = 43). In comparison with single doses, this response was almost absent after 7 days of dosing. Leucocytosis (increases up to about 1.5 x 10(9)/l after 5 and 10 mg) was similarly transient and reversible after multiple dosing.

CONCLUSIONS

Single oral doses up to 5 mg CF101 and repeated doses up to 4 mg 12-hourly for 7 days were safe and well-tolerated. Multiple-dose CF101 pharmacokinetics were unchanged and predictable from single-dose estimates, and were linearly proportional to dose. Increases in heart rate and neutrophil count were reversible during multiple dosing and were not dose-limiting in the repeat dose study. CF101 warrants further study for its efficacy in treating human disease.

Safety, tolerability and pharmacokinetics of subcutaneous Å6, an 8-amino acid peptide with anti-angiogenic properties, in healthy men

AIMS

To assess the safety, tolerability and pharmacokinetics of subcutaneous A6, an 8-amino acid peptide with anti-angiogenic properties, in healthy men.

METHODS

Double-blind, placebo-controlled, parallel-group, dose-rising, phase I study of single and repeated doses. In the single dose phase, successive groups of 5 subjects received A6 15, 35, 75, 150, 300 mg, or placebo, as subcutaneous injections in the upper thigh. In the repeat dose phase, 2 groups of 6 subjects received repeat doses of A6 35 mg and 75 mg, or placebo, and 1 group of 5 subjects received 150 mg, or placebo, 12-hourly for 6 days (11 doses in total). In each group, 4 subjects received active treatment, the remainder placebo. Pharmacokinetics of A6 were assessed up to 24 h after single doses, for 12 h after the first of the repeated doses, and up to 24 h after the last of the repeated doses.

MATERIALS

A6 for subcutaneous injection in phosphate buffer, pH 5.6-6.0. Phosphate-buffered saline was used as placebo.

RESULTS

All dose regimens of A6 were safe and well-tolerated, both systemically and locally. Time to peak plasma concentration was similar (0.5-2.1 h) in all dosage groups. Cmax and AUC(0-inf) were linearly proportional to dose. Mean Cmax ranged from 454-10,333 ng/ml and mean AUC(0-inf) from 1,690-43,371 ng x h/ml after the 15 and 300 mg single doses, respectively. Terminal t(1/2) was 1.4-1.8 h, and there was no evidence of unexpected drug accumulation. Urinary excretion of unchanged A6 was 94.6% (SD 20.7) after the 300 mg single dose (0-24 h collection), and 78.4% (SD 13.0) after the 150 mg repeated dose (0-12 h collection). A6 did not trigger production of anti-A6 IgG antibodies within 14 days of the first dose.

CONCLUSION

Single doses of A6 up to 300 mg, and repeated doses up to 150 mg, were well-tolerated and safe in healthy young men. A6 was rapidly absorbed; it was eliminated, mainly unchanged, in urine. Plasma concentrations were dose-proportional. A6 did not trigger an early immunogenic response.

Pharmacokinetics, safety and tolerability of three dosage regimens of buccal adhesive testosterone tablets in healthy men suppressed with leuprorelin

We used a randomised, double-blind, crossover design to evaluate the pharmacokinetics, safety and tolerability of three doses of buccal adhesive testosterone tablets (BATT). Twenty-four healthy men, whose endogenous testosterone was suppressed to </=5.38 nmol/l with leuprorelin acetate, took BATT (10, 20 or 30 mg) daily for 10 days. There was a 4-day washout between treatments. Substantial testosterone absorption occurred from BATT, and mean serum testosterone, free testosterone and dihydrotestosterone (DHT) concentrations over 24 h showed circadian variation. Steady state was reached by day 5. Average 24-h concentrations for the three BATT doses were within the normal range for eugonadal men: testosterone 11.67-14.57 nmol/l, free testosterone 0.026-0.33 nmol/l and DHT 1.66-2.03 nmol/l. On all three doses, peak testosterone and free testosterone was reached 8-9 h after tablet application; DHT peaked about 1-2 h later, and declined more slowly. Hormone concentrations increased with BATT dose, but increases were less than dose-proportional. There was no evidence of testosterone accumulation. BATT was well tolerated.

Bisoprolol: studies of potential interactions with theophylline and warfarin in healthy volunteers

Many patients receiving bisoprolol treatment might also require warfarin or theophylline therapy. Two studies were carried out in healthy volunteers to investigate the possibility that bisoprolol might interact with warfarin or theophylline, both of which have low therapeutic ratios. In a balanced, two-way, crossover study, eight men and four women took bisoprolol 10 mg daily for 14 days. They were divided into two groups of six volunteers. On the tenth day of treatment, six subjects received theophylline 375 mg (Nuelin tablets) by mouth and the pharmacokinetics of theophylline were determined. After a washout period of 7 days, they also underwent determination of single-dose theophylline kinetics. The other six subjects had single-dose theophylline kinetics determined 7 days before the first dose of bisoprolol, and then again after 10 days of bisoprolol treatment. Concurrent administration of bisoprolol did not influence the tolerability of theophylline and had no significant effect on any of the pharmacokinetic parameters for theophylline. In a separate study, 12 healthy men received warfarin daily until their prothrombin times were about 1.5 x control. They then received bisoprolol 10 mg daily p.o. for 10 days; warfarin was continued until 5 days after the end of bisoprolol treatment. Bisoprolol and warfarin treatments were well tolerated, and there was no effect on prothrombin times of either starting or stopping bisoprolol treatment. These studies show no effect of bisoprolol treatment upon theophylline pharmacokinetics, and no evidence of an effect of bisoprolol upon low-level anticoagulation with warfarin. Nevertheless, care should always be taken when changes are made in the medication of patients receiving theophylline or warfarin.

Effects of recombinant human interleukin-12 on eosinophils, airway hyper-responsiveness, and the late asthmatic response

BACKGROUND

Interleukin-12 (IL-12) is a macrophage-derived cytokine that modulates T lymphocyte responses and has the capacity to suppress allergic and eosinophilic inflammation.

METHODS

We carried out a double-blind, randomised, parallel group clinical study, in which patients with mild allergic asthma were given subcutaneous recombinant human IL-12 at increasing weekly injections of 0.1, 0.25, 0.5 microg/kg (n=19), or placebo (n=20). We compared responses to inhaled allergen challenge 24 h before the first injection and 24 h after the final injection. Airways hyper-responsiveness and concentrations of peripheral blood eosinophils and sputum eosinophils were also assessed.

FINDINGS

IL-12 caused a significant decrease from baseline in the main peripheral blood eosinophil count 24 h after the fourth injection compared with placebo (p=0.0001). Sputum eosinophils were also significantly decreased 24 h after allergen challenge when treated with IL-12 compared with placebo (p=0.024). IL-12 caused a non-significant trend towards improvement in airway hyper-responsiveness to histamine, but had no significant effect on the late asthmatic reaction after inhaled allergen challenge. After administration of IL-12, four of 19 patients withdrew prematurely; two with cardiac arrhythmias, one with abnormal liver function, and a single patient with severe flu-like symptoms.

INTERPRETATION

We have shown that IL-12 lowers numbers of blood and sputum eosinophils, but without any significant effects on airway hyper-responsiveness or the late asthmatic reaction. This questions the role of eosinophils in mediating these reactions, and has important implications for development of new anti-inflammatory treatments.

Pharmacokinetics of isosorbide dinitrate in healthy volunteers after 24-hour intravenous infusion

No studies have examined the pharmacokinetics of isosorbide dinitrate (ISDN) after infusion of long duration, even though such infusions are used in patients. We therefore measured ISDN and its active metabolites, isosorbide-5-mononitrate (IS5MN) and isosorbide-2-mononitrate (IS2MN), in plasma of 9 healthy volunteers who received a continuous intravenous infusion of ISDN for 24 hours at a dose rate that lowered diastolic blood pressure by 10% during the first 30 minutes of infusion. All subjects tolerated the infusion except one who experienced intolerable headache. Five subjects received 1 microgram.min-1.kg-1, one 2 micrograms.min-1.kg-1, and two 4 micrograms.min-1.kg-1 ISDN, whereas the full rate of 6 micrograms.min-1.kg-1 was used continuously in one subject. At all infusion rates the plasma concentrations of ISDN were higher at 24 hours than at earlier times, suggesting that a steady-state condition had not been reached at that time. The same was true for the mononitrate metabolites, which reached higher plasma concentrations and were cleared more slowly than the parent compound after the end of the infusion. Apparent elimination half-lives of ISDN, IS2MN, and IS5MN were 67 +/- 10 minutes, 115 +/- 13 minutes, and 272 +/- 38 minutes, respectively. Comparison of low-rate infusions (1 and 2 micrograms.min-1.kg-1) with high-rate infusions (4 and 6 micrograms.min-1.kg-1) showed that the plasma concentration ratios at 24 hours of mononitrate metabolites to parent drug and apparent plasma clearance of ISDN were almost halved at the higher infusion rates.

The time course of binding to striatal dopamine D2 receptors by the neuroleptic ziprasidone (CP-88,059-01) determined by positron emission tomography

Positron emission tomography (PET) and 11C-raclopride were used to assess the time course of binding to central dopamine D2 receptors by the novel neuroleptic ziprasidone. In a third party blind study, six healthy male control subjects received a predose of 40 mg ziprasidone and were scanned at an interval of between 4 and 36 h post-dose. One additional subject was assigned to placebo predose and was scanned at 4 h post-dose. Binding potential (BP) was compared with that seen in the subject predosed with placebo and with that seen in nine unmedicated normal volunteers. Subjects studied up to 12 h post-dose had BPs that were greater than 2 SD less than the mean BP, indicative of extensive D2 receptor binding by ziprasidone. With increasing time between dosing and PET scanning there was a curvilinear increase in BP, so that all studies performed at or after 18 h post-dose gave BPs in the normal range (mean +/- 2 SD). Elevated prolactin levels returned to within the normal range by 18 h post-dose. PET measures of binding potential correlated significantly with serum levels of ziprasidone at the time of scanning and less significantly with absolute prolactin levels at the same time.

Interrelationships between Helicobacter pylori infection, nonsteroidal antiinflammatory drugs and gastroduodenal disease. A prospective study in healthy volunteers

Helicobacter pylori and nonsteroidal antiinflammatory drugs independently cause gastroduodenal mucosal injury but the relationship between them remains unclear. We have performed a double-blind, parallel-group, placebo-controlled prospective study in 77 healthy volunteers aged 19-35 years who were randomly allocated to indomethacin (N = 15), one of three oxicams (piroxicam, chlortenoxicam, or CHF 1194; N = 36), or placebo (N = 26). Esophagogastroduodenoscopy was performed before and after four weeks of treatment and the mucosal appearances graded. Colonization with H. pylori was established at each endoscopy and gastrointestinal symptoms were assessed by daily diary card. Seven subjects (9%) were positive for H. pylori before treatment (one placebo, one indomethacin, and five an oxicam); their H. pylori status remained unchanged. Two of 70 H. pylori-negative subjects became H. pylori-positive (2.9%), both of whom had received placebo. The endoscopic score deteriorated in 1/6 drug-treated H. pylori-positive subjects and in 0/1 taking placebo. Of the H. pylori-negative subjects whose endoscopic score deteriorated, three (13%) were taking placebo, four (28.6%) indomethacin, and eight (25.8%) an oxicam. Upper gastrointestinal symptoms were reported in eight (30.8%) of the subjects taking placebo (one subject negative for H. pylori became positive), eight (53.3%) indomethacin (one H. pylori-positive), and 10 (27.8%) an oxicam (one H. pylori-positive). There were no statistically significant differences between the H. pylori-negative and H. pylori-positive groups whether on drug or placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose dependent occupancy of central dopamine D2 receptors by the novel neuroleptic CP-88,059-01: a study using positron emission tomography and 11C-raclopride

Positron emission tomography (PET) and 11C-raclopride were used to measure the occupancy of central dopamine D2 receptors by a new neuroleptic, CP-88,059-1. In a double blind dose escalation study, seven healthy male subjects received a predose of between 2 mg and 60 mg CP-88,059-1, 5 h before PET scanning. One additional subject was assigned to placebo predose. Receptor occupancy was defined as the percentage reduction in binding potential compared with that seen in the subject predosed with placebo and with that seen in seven unmedicated normal volunteers previously studied. Binding of 11C-raclopride decreased in a dose dependent manner, and 85% dopamine D2 receptor occupancy was achieved with the highest dose of CP-88,059-1. The findings confirm that brain dopamine D2 receptors are blocked by CP-88,059-1 and suggest that an effective antipsychotic dose will be between 20 mg and 40 mg. The study high-lights the potential of positron emission tomography in the preclinical evaluation of new drugs.

Renal and general tolerability of repeated doses of nimesulide in normal subjects

The renal and general tolerability of nimesulide was studied in 16 healthy men, randomised to 4 groups of 4 subjects. The groups all underwent 2 treatment periods of 7 days each, separated by a washout period of 14 days. The second treatment period was always at a higher dosage level than the first. There were 4 dosage regimens: placebo, and nimesulide 200, 300 and 400mg, all given twice daily by mouth according to a double-blind design. The tolerability of nimesulide was assessed by regular clinical examination, nondirected questions about adverse events, haematological and biochemical screening, and daily urine testing. Plasma and urinary concentrations of Tamm-Horsfall glycoprotein (THG), urinary retinol-binding protein (RBP) and beta-N-acetyl glucosaminidase (NAG) on days 1, 3, 7, and 10 of each period were used as selective indicators of nephrotoxicity. The highest dose of nimesulide (800mg daily) was associated with abdominal pain and indigestion in 5 of 8 recipients. The 400 and 600mg daily dosages were well tolerated. There were no clinically significant alterations in the haematological or biochemical screening tests during the study, and daily urinalysis remained normal throughout. The renal toxicity tests showed no evidence of nephrotoxicity associated with the administration of nimesulide in 14 subjects. The other 2 subjects each had modest increases in either urinary THG or NAG concentrations during treatment with nimesulide 800mg daily, but the results of their other tests remained normal. The study, therefore, showed only equivocal evidence of minor renal toxicity with nimesulide 800mg daily. Nimesulide 400 and 600mg daily were well tolerated in all respects, even though these dosages are higher than those recommended for clinical use.

Clinical implications of the pharmacology of serotonin reuptake inhibitors

The selective serotonin reuptake inhibitors (SSRIs) are a tribute to the ingenuity of pharmacologists and designers of molecules. Not only do these drugs have remarkable selectivity for the reuptake of serotonin compared with other monoamines, but also they have a commendable lack of affinity for receptors including the serotonin receptor. In contrast, the classical tricyclic antidepressants (TCAs) are less specific in their pharmacological action. In addition to inhibiting the reuptake of serotonin, TCAs inhibit the uptake of noradrenaline, dopamine and tyramine, and antagonize cholinergic (muscarinic), adrenergic and histaminergic receptors. Moreover, TCAs have quinidine-like anti-arrhythmic activity and lower the seizure threshold. Clinical investigations have shown that the SSRIs have equivalent therapeutic efficacy compared with the TCAs in the treatment of depression. However, the pharmacological specificity of the SSRIs is a clinical advantage since they lack the propensity to cause dry mouth, blurred vision, urinary hesitancy, constipation, hypotension and arrhythmia. Furthermore, the SSRIs are relatively safe in overdosage. The similarities between the SSRIs are more obvious than their differences: all are highly potent and selective inhibitors of serotonin reuptake with efficacy in the treatment of depression. Nevertheless, each has a distinctive pharmacological profile. In this review the characteristics desired in an "ideal" antidepressant are examined, and the ways in which the TCAs and SSRIs fit this ideal are compared.

Cardiovascular effects of antidepressants: studies of paroxetine in healthy men and depressed patients

The classical tricyclic antidepressant drugs effectively relieve the symptoms of depression, but they have the potential to be severely toxic to the cardiovascular system--including postural hypotension after therapeutic doses and lethal arrhythmias after overdosage. Paroxetine has been shown to be of similar efficacy to the tricyclic antidepressants but has lower cardiovascular toxicity in animal models and has no effects on heart rate, blood pressure or the electrocardiogram in healthy men receiving single 20-40 mg doses. The results of two contrasting studies in depressive patients and healthy men provide strong evidence that therapeutic doses of paroxetine lack any important haemodynamic or electrophysiological effects.

Clinical implications of the pharmacology of sertraline

Sertraline is slowly absorbed after oral administration, with peak plasma concentrations at 6-8 h. Plasma concentrations are linearly related to dose. The elimination half-life is about 32 h; metabolism is by demethylation to an inactive metabolite. Once-daily dosing is recommended, with steady state being reached after about 7 days. The kinetics of sertraline in the elderly and in patients with renal impairment are similar to those in young healthy female volunteers. In young male volunteers, peak plasma concentrations were lower, and elimination half-life shorter, than in elderly men or both groups of women. Nevertheless, no reduction in dosage is recommended for these groups. Sertraline is highly active in animal models of depression, and administration of the drug to healthy human beings causes a selective, dose-related inhibition of 5-hydroxytryptamine (5-HT) uptake into blood platelets. Single doses of sertraline in volunteers caused changes in the quantitative pharmaco-electroencephalogram suggesting antidepressant and anxiolytic actions, with sedative potential evident only at doses of 200 mg or more. Sertraline does not impair psychomotor performance, including simulated car driving, and overall seems neither stimulating nor sedating: an increase in critical flicker fusion threshold suggests a slight alerting effect, whereas subjective tests indicate an increase in perceived sedation at doses of 100 mg or more. No potentiation of the effects of ethanol has been noted in either young or elderly subjects. No adverse effects on the electrocardiogram, blood pressure, or systolic time intervals have been detected, and sertraline lacks anticholinergic action. These studies imply a low probability of adverse central nervous and cardiovascular effects. Sertraline is probably a weak inducer of hepatic microsomal enzyme activity. Sertraline does not affect the clearance of lithium but there may be a pharmacodynamic interaction which leads to increased tremor when the drugs are given together. No clinically relevant effects were noted in the interaction studies with digoxin, atenolol and diazepam. The pharmacokinetics and pharmacodynamics of sertraline are generally favourable. However, caution is needed when sertraline is given to patients receiving lithium or drugs with a low therapeutic ratio, such as corticosteroids, oral hypoglycaemic agents, and warfarin.

A pharmacokinetic and dynamic study of single nightly doses of conventional and controlled release formulations of trazodone

We studied the pharmacokinetics and dynamics of single evening oral doses of conventional capsules (100 mg) and a controlled release formulation (150 mg) of trazodone in 12 fasting and non-fasting young healthy volunteers. When corrected for the different doses used, there was no significant difference among the areas under the plasma concentration-time curves (AUC) for the conventional capsules and the controlled release tablets under fasting and non-fasting conditions. Both conventional and controlled release formulations were followed by a reduction in critical flicker fusion threshold (CFFT) and this effect was not influenced by the administration of food before dosing. After both conventional and controlled release formulations, blood pressure was significantly lower when medication had been given in the fasting state than when it had been given after food. The frequency of adverse symptoms was greater after the controlled release (150 mg) than after the conventional (100 mg) formulation. We conclude that there is no obvious advantage to the controlled release formulation (150 mg) and that conventional trazodone (100 mg) should be taken after food when it is given at night.

Ethics of evaluation of new drugs in human volunteers

Experiments in human volunteers are a vital part of the evaluation of most new drugs. Are such experiments ethical? This question is discussed in the light of four ethical principles: justice, beneficence, non-maleficence and respect for autonomy. Problem areas include recruitment of volunteers, obtaining consent, payment for participation and special groups such as students and staff of research institutions, the poor, women of child-bearing potential, children and elderly volunteers. Drug evaluation in volunteers does present ethical difficulties, but none of these is insurmountable.

Clinical pharmacology of moclobemide, a new reversible monoamine oxidase inhibitor

The clinical pharmacology of the new reversible monoamine oxidase (MAO) inhibitor, moclobemide, was examined in three separate studies in healthy male volunteers. In a single oral dose study, moclobemide (25-150 mg) was rapidly absorbed from the gastrointestinal tract and had a relatively short plasma half-life (mean 1.3 h after 150 mg). A decrease in the plasma concentrations of the noradrenaline metabolite 4- hydroxy-3-methoxyphenylglycol (HMPG), however, indicated a longer time to peak pharmacodynamic effect and longer duration of activity. Assay of platelet MAO activity did not reveal any evidence of irreversible inhibition of the B form of the isoenzyme. Single oral doses of moclobemide (150 and 300 mg) significantly lowered the threshold to the cardiovascular effects ('cheese reaction') of intravenous tyramine. However, after repeated administration of 100 mg three times daily for over 2 weeks, moclobemide caused significantly less potentiation than did phenelzine (15 mg three times per day) on the cardiovascular effects of oral tyramine, a clinically more relevant model. The MAO-B inhibitor, selegiline (5 mg once daily), also lowered the oral tyramine threshold significantly. Moclobemide was generally well tolerated by these healthy volunteers.

Betaxolol and glucose-insulin relationships: studies in normal subjects taking glibenclamide or metformin

1. The potential interaction between selective beta 1-adrenoceptor blockers and sulphonylureas or biguanides was studied by comparing the beta 1-adrenoceptor antagonist betaxolol with placebo in 12 normal subjects taking glibenclamide or metformin in a single-blind crossover group study. 2. After a 4 day run-in period on no treatment, six subjects took glibenclamide 2.5 mg twice daily, and six subjects took metformin 850 mg twice daily from day 5 to day 19. All subjects took betaxolol 20 mg daily from day 10 to day 13, and placebo from day 5 to day 10 and from day 13 to day 19. 3. Plasma glucose and insulin concentrations were measured fasting and 60 min after a standard breakfast for 3 successive days during each study treatment; plasma potassium, sodium and betaxolol concentrations were also measured. 4. Fasting glucose, insulin and potassium concentrations did not differ significantly between betaxolol and placebo treatment periods in either glibenclamide- or metformin-treated groups. Post-prandial glucose and insulin concentrations were lower and higher, respectively, relative to fasting concentrations but there was no significant difference between any of the treatment periods. Glibenclamide produced significant increases in insulin concentrations compared with drug-free periods (P less than 0.01). Plasma potassium and sodium concentrations were not affected by any of the treatments. 5. Plasma betaxolol concentrations were adequate for beta 1-adrenoceptor blockade. 6. This study suggests that selective beta 1-adrenoceptor blockade with betaxolol does not change fasting or post-prandial glucose-insulin relationships during simultaneous treatment with either the sulphonylurea glibenclamide or the biguanide metformin.

Lornoxicam, indomethacin and placebo: comparison of effects on faecal blood loss and upper gastrointestinal endoscopic appearances in healthy men

Forty-five healthy men aged 21-34 years took part in a double-blind, parallel-group, placebo-controlled study of the effects of 28 days' treatment with lornoxicam 4 mg twice daily or indomethacin 50 mg twice daily on faecal blood loss and the endoscopic appearances of gastric and duodenal mucosa. After an initial endoscopic examination, subjects received, intravenously, on day 0, autologous erythrocytes labelled with 51Cr. Complete daily faecal collections were then made from days 6-12, 20-26 and 34-40. The drug treatments or placebo were given from days 13-41. Faecal blood loss was calculated from 51Cr-specific activity of blood and faeces. Endoscopy was repeated 4-8 hours after the last dose of medication; mucosal appearance was graded on a 5-point scale. Lornoxicam caused no more adverse events than placebo; indomethacin caused more indigestion and central nervous system effects, and one subject in this group was withdrawn from the study. Median total blood losses during the pre-treatment and the second and fourth weeks of treatment were respectively 3.33, 3.95 and 5.71 ml for lornoxicam, 2.87, 7.04 and 7.75 ml for indomethacin, and 4.55, 3.64 and 4.13 ml for placebo. Differences between treatments were not statistically significant (P = 0.081 for second week of treatment, P = 0.383 for fourth week of treatment; Kruskal-Wallis test). The effect of chlortenoxicam on faecal blood loss in this study was thus intermediate between placebo and indomethacin, but within- and between-subject variability was such that the differences were not statistically significant. Endoscopic findings were normal in most subjects before and after all treatments, but indomethacin was associated with a slightly greater deterioration in endoscopic score and was the only treatment associated with Grade 3 appearance (in a single patient) in post-treatment endoscopy.

A double-blind placebo-controlled study of the efficacy and tolerability of ebastine against hayfever in general practice patients

Ebastine is an H1 antihistamine. Using a double-blind, parallel group randomized study design, the efficacy and the tolerability of oral ebastine (10 mg daily escalating to 40 mg daily according to clinical need) was compared over 4 weeks during 1986 with matching placebo in 40 general practice patients suffering from hayfever. Ebastine (19 patients) was more effective (P less than 0.05) than placebo (21 patients) against symptoms of running nose, itching nose, sneezing and blocked nose. Ebastine was superior to placebo in respect of the total symptom score as well as when judged by the investigators' and the patients' opinion of overall efficacy. Ebastine caused few adverse events, none of which resulted in a patient being withdrawn from treatment. Significantly more patients were withdrawn because of inefficacy from the placebo (n = 12) than from the ebastine (n = 3) treatment group (P less than 0.02). It is concluded that ebastine (10-40 mg daily) is an effective and well tolerated treatment for hayfever.

Oral and dermal pharmacokinetics of triclopyr in human volunteers

Blood levels and urinary excretion of triclopyr, the active ingredient in Garlon herbicides, were followed in six volunteers given single oral doses of 0.1 and 0.5 mg/kg body weight. Five of these volunteers later received dermal applications of Garlon 4 herbicide formulation equivalent to 3.7 mg triclopyr/kg body weight applied to the forearm. Following oral administration blood levels peaked at 2-3 h and declined to undetectable levels within 48 h; more than 80% of the dose was found as unchanged triclopyr in the urine. A two-compartment pharmacokinetic model was used to describe the time-course of triclopyr clearance; half-lives for the rapid initial and slower terminal phases were 1.3 h and 5.1 h respectively, and were independent of dose. Due to the slow half-life for dermal absorption (t1/2 = 16.8 h) the rapid initial elimination phase was obscured and the pharmacokinetics could be simplified by a one-compartment model. An average of 1.37% of the applied dose was recovered in the urine; when corrected for recovery after oral administration this was equivalent to an absorption of 1.65%. Triclopyr is slowly absorbed through skin and is rapidly eliminated. It has very low potential to accumulate in man or to be absorbed through the skin in acutely toxic amounts.

Research and development of new medicines

In order that a new chemical entity may be marketed as a drug its pharmacological effects must first be evaluated using animals. Its bioavailability must also be determined and toxicological studies are performed to assess its acute and chronic toxicity, mutagenicity, effects on fertility, perinatal effects, teratogenicity and carcinogenicity. If the results of efficacy and toxicity studies in animals are favourable, the drug is then tested in a few human volunteers, followed by pilot studies and large-scale clinical trials. Regulations that control how these trials are performed are considered. The licensing of drugs in the UK, USA and Europe is compared.

Cardiovascular (ECG and systolic time intervals) and anticholinergic effects of repeated doses of femoxetine--a comparison with amitriptyline and placebo in healthy men

1. The cardiovascular and anticholinergic effects of femoxetine and amitriptyline were compared with those of placebo in a double-blind cross-over trial in 12 healthy men. The daily doses administered were therapeutic: 600 mg femoxetine and 150 mg amitriptyline. Duration of treatment with each drug was 13 days. 2. The statistically significant effects on systolic time intervals and ECG comprised a larger decrease of QS2 index during femoxetine than during amitriptyline, and an increase of PEP/LVET ratio and QRS duration by amitriptyline. These results suggest that femoxetine and, to a lesser extent, amitriptyline increase contractility compared with placebo, and amitriptyline, but not femoxetine, causes delay in intracardiac conduction. 3. The effects of amitriptyline on the systolic time intervals are difficult to interpret because of the changes in heart rate and intracardiac electrical conduction caused by the drug. These problems of interpretation are discussed. 4. No significant changes in blood pressure were observed. The heart rate during both femoxetine and amitriptyline periods was significantly faster than during the placebo period, amitriptyline causing a significantly greater increase. 5. Salivary secretion was decreased more by amitriptyline (26%) than by femoxetine (8%), the latter being not significantly different from placebo. Femoxetine tended to increase pupil diameter and amitriptyline to increase accommodation near point, but no visual disturbances were reported on any treatment. Symptoms such as dry mouth, constipation and sedation were significantly less frequently reported during femoxetine than during amitriptyline treatment.

A multicentre open comparison of isosorbide-5-mononitrate and nifedipine given prophylactically to general practice patients with chronic stable angina pectoris

A total of 126 patients from general practice with chronic stable angina pectoris entered the treatment phase of this open, randomized, crossover comparison of 20 mg isosorbide-5-mononitrate, and 20 mg nifedipine. Both treatments were given orally, three times daily, for 4 weeks and sublingual administration of glyceryl trinitrate was allowed throughout. Over the whole treatment period, there was no statistically significant difference between treatments for anginal attacks. However, significantly fewer glyceryl trinitrate tablets were required by patients receiving prophylaxis with nifedipine, although this difference was too small to be of clinical significance. No statistical difference existed between treatments in respect of scores for 'overall intensity of pain', 'physical exercise ability' and 'general well-being'. Of those patients who expressed a preference, the majority preferred the second treatment with no statistically significant difference between isosorbide-5-mononitrate and nifedipine. Both treatments showed similar levels of adverse events, the major difference (not significant) being for flushing of the skin which occurred in five patients given nifedipine compared with one patient given isosorbide-5-mononitrate. It is concluded that, in clinical terms, the two treatments were similar. Headache and dizziness/giddiness were the most frequently recorded adverse events.

High-performance liquid chromatographic method for the radiometric determination of [14C] bucromarone in human plasma utilizing non-radiolabeled bucromarone as an internal standard

A novel radiometric high-performance liquid chromatographic (HPLC) method was developed for the determination of [14C]bucromarone in human plasma. The procedure involved the addition of non-radiolabeled bucromarone hydrochloride to each plasma sample as an internal standard; the plasma sample was then extracted, and the bucromarone was separated from its metabolites and endogenous compounds by reversed phase HPLC. The concentration of [14C]bucromarone in each plasma sample was calculated from the ratio of the amount of radioactivity in the eluate fraction corresponding to bucromarone and the peak height of the ultraviolet absorbance (210 nm) of the non-radiolabeled bucromarone used as an internal standard. The lower limit of quantitation for bucromarone free base in this assay was 8 ng/ml when [14C]bucromarone succinate had a specific activity of 0.5 microCi/mg. The coefficients of variation for the experimentally determined concentrations of bucromarone in spiked plasma samples were 6.8 and 14.3% at concentrations of 80 and 20 ng/ml, respectively. This method was used to determine concentrations of bucromarone in the plasma of healthy volunteers who were given intravenous infusions of [14C]bucromarone succinate. In general, the methodology should be applicable to any radiolabeled compound that possesses appreciable ultraviolet absorbance.

Alfuzosin and the venous reflex response: studies in normal subjects

1. Alfuzosin is a post-synaptic alpha-adrenoceptor antagonist with antihypertensive and peripheral vasodilator properties. 2. We measured the effect of alfuzosin, 5 mg, on sympathetically-mediated venoconstriction by changes in the venous reflex response (VRR) in a randomised, double-blind, placebo-controlled, crossover study in a group of 10 healthy volunteers. 3. There was a significant inhibition of the VRR after alfuzosin compared with placebo (P less than 0.001) which was present 1 h after the dose and still evident at 6 h. 4. Supine blood pressure was significantly lower (P less than 0.01) and supine heart rate was significantly higher (P less than 0.001) after alfuzosin compared with placebo. 5. Inhibition of the VRR by alfuzosin was observed to precede the development of reflex tachycardia.

Trazodone conventional and controlled-release formulations: pharmacodynamic effects after single and repeated administration

In a double-blind study, the pharmacodynamic effects of single and repeated doses of two formulations of trazodone were compared in 14 healthy young volunteers (6 men and 8 women). They received either 100 mg trazodone conventional capsules or 150 mg controlled-release tablets daily at 08.00 hours for two 7-day periods separated by a 'wash-out' period of 2 weeks. Blood pressure standing and lying, critical flicker fusion frequency and manual dexterity were measured on Days 1 and 7 of each session before and at intervals up to 8 hours after the dose. Manual dexterity was tested by measuring the time taken to drop 50 airgun pellets down a narrow tube. A daily pre-dose blood sample was also taken for measurement of trazodone to check compliance and to confirm that steady state had been achieved. Steady state plasma concentrations were reached by Day 2 of repeated dosing on both treatments. There was a trend towards shorter duration of the expected depressant effect of trazodone on critical flicker fusion frequency and manual dexterity on Day 7 for both treatments, which was significantly different between treatments for manual dexterity (p less than 0.001): for the controlled-release tablet, manual dexterity performance was better on Day 7 than on Day 1 at all times after dosing, whereas for the conventional capsule manual dexterity was worse on Day 7 than on Day 1 until 4 and 8 hours after dosing, when performance was better than on Day 1. In this study, both formulations of trazodone caused the expected negative effects on psychomotor function. Further studies would be required to confirm the apparent advantage of the controlled-release tablet in the test of manual dexterity.

The cardiovascular effects of antidepressants

This monograph comprises a review of the cardiovascular effects of the various types of antidepressant drugs in clinical use. The frequency, severity and clinical importance of these effects are placed in perspective. Most antidepressants can cause changes in blood pressure. Both the tricyclic type (TCA) and the monoamine oxidase inhibitors (MAOIs) can produce postural hypotension which may be dose-limiting. In addition, the MAOIs may be associated with severe hypertension when amine-containing foods or medicines are ingested. It is unlikely that therapeutic doses of any available antidepressant drug could impair cardiac contractility. Typical TCAs can cause abnormalities of cardiac conduction and arrhythmias, but this affects less than 5% of patients, mostly to a clinically insignificant extent. Newer compounds such as lofepramine, mianserin, trazodone and viloxazine seem safer in this respect. Reports of an association between therapeutic use of TCAs and sudden death are far from convincing. Overdosage with the MAOIs, lithium and carbamazepine is dangerous but not common; overdose with a TCA is a major source of morbidity and mortality. Lofepramine, mianserin and trazodone are relatively safe in overdose. The use of various antidepressants in patients with hypertension, cardiac failure, angina pectoris, myocardial infarction, or cardiac arrhythmias is discussed and guidelines suggested for the selection and use of antidepressant medication.

Chlortenoxicam pharmacokinetics in young and elderly human volunteers

The pharmacokinetics of chlortenoxicam, a new non-steroidal anti-inflammatory drug, have been compared in young and elderly healthy human volunteers. Chlortenoxicam was found to have a relatively short mean elimination half-life of about 4 hours, with considerable inter-subject variability, but there was no significant difference between young and elderly subjects. There was no evidence of accumulation with repeated administration. No unchanged chlortenoxicam was found in urine from any subject, suggesting that it undergoes extensive metabolism in man.

Correction of systolic time intervals for heart rate: a comparison of individual with population derived regression equations

1. We have examined the problem of how systolic time intervals (STI) should be corrected for heart rate in clinical pharmacological studies. 2. 'Individual' linear regression equations describing the relationship between STI and heart rate were derived for each of 43 healthy young adults (30 men and 13 women) by measuring STI at different heart rates produced by incremental doses of intravenous atropine. 'Population' equations for each sex were obtained by taking the mean of the 'individual' regression coefficients. 3. In order to assess which method more effectively reduced variability of the STI, 'individual' regression coefficients were derived for eight men who had previously participated in a placebo-controlled study which had used STI to test the cardiovascular effects of calcium antagonists alone and in combination with propranolol. 4. Within-subject variability in rate-corrected STI was similar after application of 'individual' and 'population' regression equations. Between-subject variability tended to be less after the use of 'population' equations. 5. 'Population' regression equations were more effective than 'individual' regression equations in allowing detection of differences between treatments, as judged by F values from ANOVA. 6. In clinical pharmacological studies including measurements of STI in healthy young subjects, 'individual' regression equations appear to have no advantage over 'population' equations derived in a group of subjects of similar age and sex.

Recent developments in the use of nitrates for treatment of angina pectoris

Organic nitrates are effective in the treatment and prophylaxis of angina pectoris. The major clinical problem of tolerance may be avoided if the daily plasma concentrations of the active metabolite, isosorbide-5-mononitrate are maintained at 100-300 ng/ml. The most promising development in achieving this is the use of sustained release preparations.

Pharmacokinetics of loxiglumide after single intravenous or oral doses in man

Loxiglumide (D,L-4-(3,4-dichlorobenzoylamino)-5-(N-3-methoxypropyl-pentylam ino)-5-oxo-pentanoic acid, CR 1505) was given intravenously to 8 male healthy volunteers in a single dose of 2 mg/kg body weight (b.w.) or orally in a single dose of 5 mg/kg b.w. Loxiglumide was measured in plasma and in urine by HPLC during 48 h following the administration. After i.v. infusion the plasma levels were consistent with an open two-compartment pharmacokinetic model represented by the equation C (mg/l) = 43.791 x e-2.652 x h + 2.657 x e-0.139 x h. In the urine, besides loxiglumide, two metabolites were found and in the 48 h following the i.v. administration the urinary excretion of loxiglumide and of its metabolites accounted for 11.13% of the administered dose. After oral administration loxiglumide appeared in plasma with a lag time of 14 min, reached the peak 34 min after administration, being eliminated with an initial fast and a terminal slow elimination rate. The plasma levels were consistent with an open two-compartment pharmacokinetic model represented by the equation C (mg/l) = -46.72 x e-8.765 x (h-0.23) + 40.660 x e-1.383 x (h-0.23) + 6.057 x e-0.120 x (h-0.23). In the urine, besides loxiglumide, two metabolites were found and in the 48 h following the oral administration the excretion of loxiglumide and of its metabolites accounted for 7.67% of the administered dose. The absolute bioavailability of loxiglumide was calculated comparing the AUC(0-inf) found after oral and after i.v. administration and was estimated as 0.967, with p = 0.05 fiducial limit of 0.656-1.278.

Pharmacokinetics of flupirtine in elderly volunteers and in patients with moderate renal impairment

The pharmacokinetics of flupirtine after a single oral dose of 100mg have been studied in patients with moderate renal impairment and in healthy elderly subjects aged 66-83 years. Mean elimination half-life of flupirtine was higher in elderly patients than in younger normal subjects, and this was associated with an increased maximum serum concentration and reduced clearance. The mean half-life in patients with renal impairment was higher than in normal subjects. There was no correlation between observed elimination half-life and degree of renal impairment, but the creatinine clearance of most patients fell in a narrow range between 43 and 60 ml/min. In the light of these results and until further information is available, it would be prudent to start treatment of patients who are elderly or have evidence of renal impairment with half the dose of flupirtine recommended for younger patients with normal renal function.

Pharmacokinetics of indoramin and its 6-hydroxylated metabolite after repeated oral dosing

The pharmacokinetics of indoramin and its active 6-hydroxylated metabolite have been studied in healthy male volunteers after repeated oral dosing with 37.5 mg twice daily for 2 weeks. Plasma concentrations of indoramin accumulated, on average, three to four-fold above those anticipated on the basis of the kinetics after the first dose, though steady state was achieved by the end of the first week and no further increase was observed after 2 weeks. The degree of accumulation was consistent between subjects, with a highly significant (p less than 0.001) correlation between the concentration 2 h after a single dose and the average steady-state concentration. Possible explanations for the accumulation of indoramin are discussed. Plasma concentrations of 6-hydroxyindoramin, in contrast, did not accumulate on multiple dosing. At steady state, concentrations of the metabolite, as represented by the AUC0-8h, were approximately 30-40 per cent of those of the unchanged drug. Since the two compounds are approximately equipotent the metabolite may accounts for 25 per cent of the hypotensive activity of indoramin during a typical clinical regime of 37.5 mg twice daily.

The effect of repeated oral doses of azelastine hydrochloride on antipyrine half-life in normal volunteers

Treatment with azelastine 4.4 mg twice daily for 21 days did not produce any change in salivary antipyrine elimination in 8 normal volunteers.

Comparison of gastrointestinal blood loss in healthy male volunteers during repeated administration of standard and sustained action tiaprofenic acid and sustained release indomethacin

Gastrointestinal blood loss was measured in 30 healthy male volunteers before and during 4 weeks of oral treatment with either tiaprofenic acid tablets 300 mg twice daily, tiaprofenic acid sustained action (SA) capsules 600 mg once daily, or indomethacin sustained release (SR) capsules 75 mg once daily, in an open parallel-group study of 38 days' duration. Autologous erythrocytes labelled with 51Cr were given intravenously on the first study day. Gastrointestinal blood loss was measured by comparing faecal and red blood cell 51Cr activity during the second and fourth weeks of drug treatment. Blood loss was significantly greater during treatment with all 3 active preparations than during the pretreatment period, but this comparison is of limited value because placebo was not given in parallel and because in 4 subjects, who had to have their erythrocytes relabelled, there was no pretreatment data. The tiaprofenic acid SA group had consistently lower blood loss than the tiaprofenic acid tablet group. Both these groups also had consistently lower blood loss than the indomethacin SR group, although the difference between the treatment groups was not significant. Blood loss during the fourth week of treatment was less than during the second week of treatment for both the tiaprofenic acid SA and indomethacin SR capsule groups. With tiaprofenic acid tablets, blood loss was very similar at weeks 2 and 4 but this result should be viewed with caution because data at week 2 were missing for 3 subjects. Thus, formulation of tiaprofenic acid as a sustained action capsule does not appear to increase gastric irritancy as measured by faecal blood loss.

Comparison of flupirtine and indomethacin on frusemide-induced diuresis

A single oral dose of flupirtine maleate, a novel analgesic agent, did not antagonize significantly the diuretic action of frusemide when compared with indomethacin and placebo in normal human volunteers.

Evaluation of possible interactions between ethanol and trazodone or amitriptyline

The pharmacodynamic effects of single doses of trazodone (100 mg), amitriptyline (50 mg) or placebo either alone or with ethanol (0.5 ml/kg) were investigated in 6 healthy volunteers in a double-blind crossover study. Plasma concentrations of the drugs and ethanol were also measured. Pharmacodynamic tests were critical flicker fusion frequency threshold (CFF), choice reaction time (CRT), manual dexterity, a digit span test and visual analogue scales. Blood ethanol concentrations were not influenced by the co-administration of either antidepressant. tmax for trazodone was prolonged by ethanol but the other pharmacokinetic parameters for trazodone and amitriptyline were not influenced by ethanol. Trazodone and amitriptyline caused the expected profound depressant effects on CFF, CRT, manual dexterity and on the rating scales for drowsiness, 'clearheadedness', aggression and disinhibition. Ethanol alone impaired manual dexterity, increased drowsiness, reduced 'clearheadedness' and also tended to reduce feelings of aggression. In combination with either trazodone or amitriptyline, ethanol caused little additional effect except in the case of manual dexterity, which was further impaired. This result may reflect the profound effects of the antidepressants alone and does not suggest that it is safe for patients receiving antidepressant medication to take ethanolic drinks.

The pharmacokinetics and dynamics of oxprenolol: a simulation study with six subjects

Experimental results of plasma concentration determinations and lowering of exercise heart rate for six subjects taking a conventional tablet and a sustained release preparation of oxprenolol have been analysed by a comprehensive computer simulation model. Individual plasma values were simulated using a lest squares procedure and the results were applied to evaluate individual release patterns following dosage with the sustained release preparation. Application of the model to the lowering of exercise heart rate indicated that the response is in a steady state with the plasma values and that the response-concentration relation is of the saturable, Emax, type. The parameters for this were evaluated for each subject for the results after a dose of a conventional tablet. These parameters were applicable to the results after dosage with a sustained release preparation. The method should be applicable to other sustained release preparations.

A multiple dose comparative study of the pharmacodynamic and pharmacokinetic behaviour of polymer-matrix and Oros dosage forms of oxprenolol in healthy volunteers

A new osmotic drug delivery system (Oros) has been evaluated in multiple-dose studies in young healthy volunteers as a sustained-release vehicle for once-daily administration of oxprenolol. Two Oros systems were examined in two separate studies, one containing 170 mg oxprenolol succinate with an initial zero-order release rate of 10 mg/h, and the other containing 260 mg oxprenolol succinate with an initial release rate of 16 mg/h. These were compared respectively with conventional oxprenolol hydrochloride (Trasicor) 80 mg twice daily and polymer-matrix oxprenolol hydrochloride (Slow Trasicor) 160 mg once daily. Variations in mean plasma levels and beta-adrenoceptor blockade (measured by inhibition of exercise tachycardia) were considerably reduced on the 10/170 Oros once-daily compared with the Trasicor 80 mg twice-daily regimen. With both formulations there was no significant change in mean plasma concentrations or areas under the curve after 8 days' treatment, and similar pre-dose plasma concentrations were obtained. There was significant inhibition of exercise tachycardia throughout 24 h after the 10/170 Oros on the eighth day. The 16/260 Oros system gave smoother pharmacokinetic and pharmacodynamic profiles, and on repeated dosing a higher mean pre-dose plasma oxprenolol concentration than Slow Trasicor. Drug availability was similar for the two dose forms, suggesting an acceptable level of absorption of oxprenolol from most of the gastrointestinal tract. On the eighth day exercise heart rate was significantly reduced throughout 24 h with 16/260 oxprenolol Oros, but only between 1 and 15 h with Slow Trasicor.

Single-dose pharmacokinetic and pharmacodynamic comparison of polymer-matrix (Slow Trasicor) and Oros dosage forms of oxprenolol in healthy volunteers

Oxprenolol was administered in single doses by mouth to healthy volunteers either in a polymer-matrix slow-release formulation (Slow Trasicor) or in osmotic drug-delivery systems (oxprenolol Oros). Plasma oxprenolol concentrations and heart rates after exercise were measured. Plasma concentrations of the drug were maximal at 3 h but negligible at 24 h after administration of Slow Trasicor. Following ingestion of the Oros systems measurable concentrations were maintained throughout 24 h. Significant reduction of exercise-induced tachycardia persisted for 24 h after administration of oxprenolol Oros. With Slow Trasicor heart rate responses had returned to baseline values by this time. The osmotic drug-delivery systems appear to sustain significant beta-adrenoceptor blockade for 24 h after a single oral dose.

Comparison of single-dose pharmacokinetic and pharmacodynamic properties of two metoprolol Oros systems with different initial zero-order release rates

Plasma concentrations and haemodynamic effects at rest and during exercise have been measured in six healthy volunteers after single oral dosing with two Oros drug delivery systems containing 190 mg metoprolol fumarate but with initial release rates of 14 and 19 mg/h, respectively. Sub-maximal exercise heart rates were attenuated by both Oros systems throughout most of the 30 h study period but no significant differences were detected between the 14/190 and 19/190 forms. Resting pulse rates and blood pressure were similarly affected by the Oros preparations. Approximately the same amount of drug reached the circulation from the Oros systems, but the 19/190 form produced higher peak concentrations at earlier times after dosing. At 24 h higher plasma concentrations were observed for the 14/190 preparation, reflecting its longer duration of drug release. There was no apparent advantage of one form over the other as regards haemodynamic response. The reduced peak plasma concentration with 14/190 Oros may, however, be an advantage in terms of tolerability.

Influence of site of drug delivery on the systemic availability of metoprolol: comparison of intragastric infusion and 14/190 Oros administration

The influence of the site of drug delivery on the systemic availability of metoprolol has been evaluated by measuring plasma drug concentrations in six healthy volunteers after administration of a continuous 13.5 h intragastric infusion and a 14/190 Oros controlled-release dosage form, on two separate occasions. The same total amount of drug was administered at the same rate on both occasions but the Oros system moved through the gut whereas the site of the infusion was constant. The differences between treatments were confined largely to the period 6-15 h after dosing when lower plasma concentrations were obtained after administration of the Oros system. The levels after 20 h were higher for Oros, however, reflecting its longer duration of drug release. The amount of drug reaching the circulation was 19.8% less for the Oros preparation compared with intragastric infusion but this was not due to incomplete release since the residual amounts of drug in three systems recovered from faeces corresponded to less than 12% of the administered dose. Analysis of the plasma profiles by the Wagner-Nelson method indicated a reasonable agreement between in vitro release and in vivo absorption. The appearance of drug in plasma was delayed for both treatments, and for Oros the apparent absorption rate slowed 6 h after dosing. Plasma profiles after 14/190 metoprolol Oros were consistent with prolonged in vivo delivery and absorption from the gut. The absorption process, however, was associated with some reduction both in the rate, after 6 h, and in the total amount reaching the circulation.

An evaluation of possible interactions between ethanol and trazodone or amitriptyline

The pharmacodynamic effects of single doses of trazodone (100 mg), amitriptyline (50 mg) or placebo either alone or with ethanol (0.5 ml/kg) were investigated in six healthy volunteers in a double-blind crossover study. Plasma concentrations of the drugs and ethanol were also measured. Pharmacodynamic tests were critical flicker fusion frequency threshold (CFF), choice reaction time (CRT), manual dexterity, a digit span test and visual analogue scales. Blood ethanol concentrations were not influenced by the co-administration of either antidepressant. tmax for trazodone was prolonged by ethanol but the other pharmacokinetic parameters for trazodone and amitriptyline were not influenced by ethanol. Trazodone and amitriptyline caused the expected profound depressant effects on CFF, CRT, manual dexterity and on the rating scales for drowsiness, 'clear-headedness', aggression and disinhibition. Ethanol alone impaired manual dexterity, increased drowsiness, reduced 'clear headedness' and also tended to reduce feelings of aggression. In combination with either trazodone or amitriptyline, ethanol caused little additional effect except in the case of manual dexterity which was further impaired. This result may reflect the profound effects of the antidepressants alone and does not suggest that it is safe for patients receiving antidepressant medication to take ethanolic drinks.