Pharmacodynamic methods for investigating antiasthma drugs in healthy volunteers.

The investigation of bronchoactive drugs in healthy volunteers may be divided into studies on the drug effects on basal airway calibre, the effects on induced bronchoconstriction and the examination of the pharmacokinetic and side effect profile of new chemical entities. In the studies presented in this paper, whole body plethysmography was used to assess the pharmacological activity of three new development compounds. In the first example, bronchodilatation was measured after administration of an anticholinergic drug. In two further examples, the bronchial effects were studied in asthma models in which an increase in airflow resistance was produced using inhaled methacholine and platelet activating factor (PAF). The method applied in these tests allowed the antagonistic effects of drugs on the constrictor effect of individual agents to be followed. Antiasthmatic drugs can also have a systemic effect on different physiological and biochemical parameters. These parameters can be applied as useful tools in the determination of the pharmacological activity of a given drug, irrespective of the conventional methods used to evaluate the efficacy of bronchodilators by the degree of bronchial muscular relaxation. A complex nonbronchial model is shown in order to demonstrate how it is possible to identify the pharmacologically effective dose of a new beta 2-adrenoceptor agonist.

Phase I clinical trials with WAL 2014, a new muscarinic agonist for the treatment of Alzheimer's disease.

The safety, tolerability and pharmacological activity of WAL 2014, a new centrally-acting M1 agonist were examined in two clinical studies (0.5-80 mg and 100-160 mg). Single increasing p.o. doses were administered to groups of 8 volunteers (6 verum, 2 placebo) each. Both studies were placebo controlled with single-blind observation within the respective dose groups. Vital functions (BP, HR, resp. rate) did not reveal any clinically significant substance-induced changes up to a dose level of 60 mg. A slight, but obvious increase in HR was measured with a dose of 80 mg and higher; a slight increase in systolic BP was registered at the dose levels of 120 and 160 mg. No substance-related alterations were observed in the laboratory tests (exception: a significant, reversible increase of the salivary fraction of alpha-amylase in 3 volunteers at the dose levels 100 mg-140 mg). The majority of volunteers reported an increased salivary secretion with doses of 40 mg and higher; this was confirmed by the greater volume of measured saliva. Furthermore, with doses of 100 mg upwards there were isolated reports of side effects such as a desire to urinate, a burning sensation on urination, increased lacrimation and nasal secretion, disturbances of accommodation, heartburn, rumbling of the stomach as well as cramps, nausea, diarrhoea, excessive sweating and palpitation. WAL 2014 did not cause any abnormal changes in the EEG. Dose dependent central effects were observed with 40, 60, 80, 100 and 140 mg treatments. Pharmacokinetic data indicate a rapid and good absorption and an absolute bioavailabitlity > or = 70%. The pharmacodynamic and side effects observed in both studies are regarded as being drug-dependent and might be due to the cholinergic activity of the compound and a weak sympathetic activation via M1 receptors. In summary, the substance did not produce any effects in the dose range tested to suggest further use in man might be inadvisable.

Neuroendocrine and side effect profile of pramipexole, a new dopamine receptor agonist, in humans.

The effects and tolerability of pramipexole, a new dopamine D2-receptor agonist, on prolactin, human growth hormone, thyrotropin, cortisol, and corticotropin levels were investigated in a randomized, double-blind, crossover study in 12 healthy volunteers. Single oral doses of 0.1, 0.2, and 0.3 mg pramipexole and placebo were studied over a period of 24 hours. Pramipexole decreased serum prolactin levels in a dose-dependent manner, with a maximum effect after 2 to 4 hours. Serum levels of human growth hormone were dose-dependently increased; however, this effect was only significant 2 hours after drug administration. Furthermore, a slight increase in serum cortisol levels and a slight decrease in serum thyrotropin levels was observed. Our findings show for the first time pharmacodynamic effects of pramipexole after single oral doses in healthy volunteers. The compound was well tolerated and showed an endocrine profile similar to other dopamine D2-agonists.

Pharmacodynamics, pharmacokinetics and safety profile of the new platelet-activating factor antagonist apafant in man.

Platelet-activating factor (PAF) is a unique phospholipid mediator with multifunctional properties. Evidence generated in experimental studies suggests that PAF plays a pathogenetic role in anaphylactic, inflammatory and immunogenic reactions. Apafant (WEB 2086, CAS 105219-56-5), a novel synthetic PAF receptor antagonist, was administered to a total of 101 healthy volunteers within 5 studies to investigate its pharmacologic activity, pharmacokinetic behaviour and safety profile. Pharmacologic activity was monitored by inhibition of 5 x 10(-8) mol/l PAF-induced platelet aggregation ex vivo. The following treatment schedules were studied: oral single dose 1.25 to 400 mg; oral multiple dose 100 mg t.i.d. over 7 days; i.v. infusion 0.5 to 50 mg (over 30 min); inhalative administration up to 1.0 mg. PAF induced platelet aggregation was virtually completely inhibited by single oral doses of 20 mg upwards, throughout during the multiple oral dose study, at all dose levels tested in the i.v. study and (significantly but not completely) at 0.5 and 1.0 mg in the inhalative study. Following oral administrations (capsules) apafant is absorbed rapidly (tmax 1 to 2 h), there is linear pharmacokinetics for the mean plasma concentrations of apafant measured by RIA as well as for the areas under the curve (AUCs). Approximately 60% of apafant is bound to plasma protein, the mean volume of distribution is 28 l, about 44% of an oral dose is excreted in the urine, the mean renal clearance is 192 ml/min. No accumulation of the drug occurred in volunteers with normal kidney function. No clinically relevant drug related adverse events or changes in laboratory or vital parameters such as blood pressure, heart rate, respiratory rate and ECG were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihistaminic activity and side effect profile of epinastine and terfenadine in healthy volunteers.

New H1-receptor antagonists are assessed not only for their H1 antihistaminic activity but also for their central nervous system (CNS) side effects. Fifteen healthy subjects received a once daily dose of 5 mg, 10 mg or 20 mg of epinastine, or a twice daily dose of 60 mg of terfenadine or placebo in a randomized double-blind (double-dummy) crossover study. The response to histamine-induced skin wheals was compared. CNS effects were evaluated by a multiple reaction time task, a finger tapping test and a self-rating scale (Bf-S von Zerssen) to assess mood state. Epinastine attenuated the wheal size in response to histamine in a dose-dependent manner. In addition, all epinastine dosages had a distinctly faster onset of action than terfenadine. All active treatments (5 mg, 10 mg, 20 mg epinastine and 60 mg terfenadine) attained their maximum effects 4 h after administration. At this time point and also 12 h after administration, 20 mg of epinastine were significantly more effective than 60 mg of terfenadine. Single 10 mg and 20 mg doses of epinastine were as effective as terfenadine given twice daily, and significantly more effective than placebo 24 h after drug administration (i.e. 12 h after the second dose of terfenadine). The psychometric tests for CNS effects did not reveal any difference among epinastine, terfenadine and placebo. In conclusion, epinastine is one of the most effective peripherally acting H1 antagonist which lacks significant CNS side effects and is suitable as a once daily dosage regimen.

Inhibitory effects of the new PAF acether antagonist WEB-2086 on pharmacologic changes induced by PAF inhalation in human beings.

Recent research on asthma mediators has concentrated more and more on platelet-activating factor (PAF), which is one of the most potent bronchoconstrictors known thus far. Inhalant PAF challenge in healthy volunteers may provide a mean of testing PAF antagonists. The usefulness of the PAF provocation test in measuring the pharmacologic activity of a new PAF antagonist, WEB-2086, has been examined in 12 healthy volunteers in a double-blind, placebo-controlled, within-subject crossover study. PAF-induced immediate bronchoconstriction, slight hemodynamic changes, and PAF-related subjective side effects. Premedication with WEB-2086 (40 mg) completely prevented any increase in airway resistance after PAF inhalation, as well as development of most of the cardiovascular and side effects induced by PAF. The clear protection against PAF-induced pharmacologic effects can be explained by the specific PAF-antagonistic activity of WEB-2086. The method described in this article may be applied as a useful tool for looking at PAF-antagonistic activity in healthy volunteers.

PAF-induced platelet aggregation ex vivo as a method for monitoring pharmacological activity in healthy volunteers.

Platelet aggregation induced ex vivo by aggregating factors such as adrenaline, ADP, collagen or PAF may be useful as a model for describing drug effects in humans. In the two studies reported here, PAF-induced platelet aggregation ex vivo was used as an indicator of the pharmacological activity in healthy volunteers of the newly developed specific PAF-antagonist WEB 2086. In intravenous and inhalative single rising dose tolerance trials this method proved useful for monitoring the pharmacological action of the compound tested. After administration of placebo no relevant pharmacological activity was observed. In both studies increasing dosages of the test substance showed clear, dose-related inhibition of PAF-induced platelet aggregation. Ex vivo PAF-induced platelet aggregation thus provides a simple and rapid means of assessing functional PAF antagonism during trials of PAF-antagonists in human volunteers.

Safety, tolerability, and pharmacologic activity of multiple doses of the new platelet activating factor antagonist WEB 2086 in human subjects.

The safety, tolerability, and pharmacologic activity of WEB 2086, a novel, specific platelet activating factor antagonist, were examined in two double-blind, placebo-controlled, within-subject crossover studies. In each study, WEB 2086 (three times 40 mg/day or three times 100 mg/day) was administered for 7 days to 12 healthy volunteers. Pharmacologic activity of the compound was monitored with ex vivo platelet activating factor-induced platelet aggregation. Multiple administration of WEB 2086 resulted in a continuous, almost complete inhibition of this aggregation. Nevertheless, no clinically significant drug-related effects on vital and laboratory parameters or obvious drug-dependent adverse reactions were observed. In conclusion, the performed studies confirmed earlier findings that WEB 2086 was an effective platelet activating factor antagonist in human beings and, furthermore, showed no side effects that would provide objections against further clinical trials with this substance in patients.

Non-invasive evaluation of hemodynamic, tremorogenic and biochemical effects in response to beta-adrenoceptor stimulation.

1, 4, 12 and 24 micrograms SOM 1397 CL, a new beta 2-adrenergic bronchodilator, were administered by inhalation to 10 healthy volunteers in a double-blind, placebo-controlled, within-subject crossover study in order to assess circulatory, tremorogenic and biochemical effects. 1 microgram SOM 1397 CL did not cause any relevant changes in the measured parameters. After administration of 4 micrograms a slight but continuous increase in tremor amplitude and c-AMP was observed. The effects on hemodynamics and other laboratory values could be considered negligible. Overdoses of 12 and 24 micrograms resulted in a dose-dependent increase in systolic blood pressure, pulse rate, tremor amplitude, alpha-AMP and lactic acid, as well as in a decrease of diastolic blood pressure and potassium. These effects may be partly attributable to beta 2-receptor stimulation. The method described in this paper can be applied as a useful tool for determination of beta 2-adrenergic activity in healthy volunteers, independent of the conventional methods which are used to evaluate efficacy of bronchodilators by the degree of bronchial muscular relaxation.

Bronchospasm induced by methacholine inhalation as a model for testing of bronchospasmolytics in healthy volunteers.

Provocation tests with acetylcholine, methacholine, histamine and carbachol are used as models for measuring bronchospasmolytics in patients with bronchial hyperreactivity. The possibilities of the methacholine provocation test for the measurement of bronchospasmolytic agents in healthy volunteers have been examined. The relevance of this method will be shown by the example of the effects of two beta 2-mimetics in comparison to placebo. Under placebo conditions, methacholine provocation resulted in an increase of bronchial resistance of approximately 200% in volunteers. The various dosages of the two test substances showed a clear, dose-related bronchospasmolysis. The described method can be used as a model of investigation for testing bronchospasmolytics in healthy volunteers.

Inhibitory effect of oral WEB 2086, a novel selective PAF-acether antagonist, on ex vivo platelet aggregation.

WEB 2086 is a novel PAF-acether antagonist, whose pharmacological action in man has only been preliminarily defined. Twelve healthy male volunteers received oral doses of 5, 30 and 90 mg and over the following 24 h inhibition of 5 x 10(-8) M PAF-acether-induced platelet aggregation ex vivo was studied as an indicator of pharmacological activity. WEB 2086 inhibited PAF-acether-induced platelet aggregation in all the doses tested, with the maximum effect 1 to 2 h after administration. After 2 h 5- 30- and 90-mg doses caused, respectively, 87, 98 and 100% inhibition. The magnitude and duration of the inhibitory effect was dose-dependent, with a significant action still detectable 10 h after administration of all three doses, and 12 h after administration of the two highest doses (30 and 90 mg). The subjects did not complain of any significant adverse effect and all completed the study.

Pharmacodynamics of the new H1-antagonist 3-amino-9,13b-dihydro-1H-dibenz[c,f]imidazo[1,5-a]azepine hydrochloride in volunteers.

The inhibitory effects of 3-amino-9,13b-dihydro-1H-dibenz[1,5-a]azepine hydrochloride (WAL 801 CL), a new H1-receptor antagonist, on histamine-induced skin wheals were studied in 9 volunteers. The study was a double-blind, randomized (Latin square) change-over, intraindividual comparison of the effects of single doses of 2,6 and 18 mg WAL 801 CL and of placebo and 2 mg ketotifen on skin wheals induced by intradermal injections of 5 micrograms hystamine 1, 2, 4, 6 and 8 h after administration of the drugs. The injection of 5 micrograms was also made prior to each drug administration. The effects on psychological performance and the subjective state were also evaluated. The following tests were employed: simple visual reaction time (RT), critical flicker fusion frequency (C3F) and von Zerssen's self-rating scale Bf-S, assessing state of mood. There was a washout period of at least 72 h between each course of treatment. A decrease in the size of the histamine wheal was observed 1 h after WAL 801 CL and was maintained for at least 8 h. The reduction in the size of the histamine wheal was between 44% (2.0 mg) and 71% (18.0 mg). After ketotifen a marked decrease in the wheal area was observed between 4 and 8 h after administration of the drug, with maximum histamine antagonism of 59% after 6 h. The inhibitory effects of 6 and 18 mg WAL 801 CL and 2 mg ketotifen were statistically significant compared with placebo. 8 of 9 subjects felt tired (subjective report) after ketotifen, corresponding changes could be detected by Zerssen's state of mood scale Bf-S, but not by other psychological performance measures (RT, C3F).(ABSTRACT TRUNCATED AT 250 WORDS)

Antihistamine activity and central effects of WAL 801 CL in man.

The tolerability and antihistaminic activity of WAL801 CL, a new, peripherally acting H1-receptor antagonist, have been evaluated in a double-blind, placebo-controlled, within-subject cross-over study. WAL801 CL 8 mg b.d. was given to 10 healthy volunteers for 15 days. It resulted in a distinct reduction in histamine wheal size and a decreased bronchoconstrictor response to histamine inhalation. No cardiovascular side effects were observed. Transient and slight fatigue was observed in 3 subjects. Psychological tests, such as simple visual reaction time, critical flicker fusion frequency and mood self rating scale, showed that WAL801 CL had no sedative side effects and that it did not alter psychomotor performance.