Drugs online research references
Br J Pharmacol. 1988 Feb;93(2):375-82.
The effects of the novel anti-anginal compound RS 43285 on myocardial conduction in the anaesthetized dog.
Allely MC, Alps BJ.
Department of Pharmacology, Syntex Research Centre, Riccarton, Edinburgh.
1. A pentobarbitone-anaesthetized canine model of myocardial conduction was developed to evaluate drug effects on intra-atrial (I-A), intra-ventricular (I-V) and atrioventricular (A-V) conduction parameters, both at rest and during electrical pacing of the right atrium or ventricle. Drug effects on the ability of the sino-atrial (SA) node to re-establish sinus rhythm on switching off electrical pacing were also considered. The effects of the novel anti-anginal compound RS 43285-193 ((+/-)-N-(2,6-dimethyl-phenyl)-4[2-hydroxy-3-(2-methoxyphenoxy)propyl] -1-piperazine acetamide dihydrochloride) were compared to those of the standard anti-anginal compounds nicardipine, nifedipine and verapamil. 2. In the dose range 15-7000 micrograms kg-1, RS 43285 had no significant effects on I-A, I-V or A-V conduction either at rest or during electrical pacing and did not affect the re-establishment of sinus rhythm. 3. Nicardipine had no effects on conduction parameters at resting heart rate. There were no effects on I-A or I-V conduction on electrical pacing but A-V conduction was increased at 200-500 micrograms kg-1 (with a 2:1 A-V conduction block in two out of six dogs); this was accompanied by a prolongation of the interval to reversion of sinus rhythm. 4. Nifedipine had no significant effects on I-A or I-V conduction but significantly prolonged A-V conduction at 1000 micrograms kg-1 and this dose also increased the interval to SA node recovery. 5. Verapamil did not effect I-A or I-V conduction.(ABSTRACT TRUNCATED AT 250 WORDS)
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3359110&dopt=Abstract
Res Commun Chem Pathol Pharmacol. 1986 Jan;51(1):59-64.
On the mechanism of the anti-hypertensive effect of Ca++-blockers.
Marmo E.
Cardiovascular effects induced by nifedipine and verapamil were examined in normo- and hypertensive animals to investigate the role of Ca++ -antagonists in antihypertensive therapy. Intra-arterial administration of nifedipine or of verapamil to anesthetized dogs by the intracerebroventricular (icv, 1 and 10 micrograms/kg in 1 min), or intravertebral (0.1 and 1 mg/kg in 5 sec) or intra common carotid artery (0.1 and 1 mg/kg in 5 sec) produced hypotension and sinus bradycardia and slightly reduced the pressor response induced by carotid occlusion. The latter effect was also reduced when the drugs were infiltrated into the walls of carotid sinuses (0.1 ml/sinus of a 1% solution). The antihypertensive effect of nifedipine and verapamil depends on their Ca++ antagonist and vasodilator properties. However, our study suggests CNS vasomotor involvement also.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3952371&dopt=Abstract
Am Rev Respir Dis. 1983 May;127(5):549-53.
Effects of nifedipine on antigen-induced bronchoconstriction.
Henderson AF, Heaton RW, Dunlop LS, Costello JF.
We have investigated the effects of the calcium antagonist nifedipine on antigen-induced bronchoconstriction in vivo and in vitro. Eight grass-pollen-sensitive asthmatics were given either nifedipine (20 mg sublingually) or placebo 30 min before antigen challenge. The fall in forced expiratory volume in one second after pretreatment with placebo was 42.8 +/- 10.1%. After nifedipine this fall was significantly reduced to 26.5 +/- 11.7% (p less than 0.005). Two in vitro models of allergic asthma have been studied: actively sensitized guinea pig tracheal strips (GPT) and passively sensitized human bronchial muscle (HBM). Contraction of GPT by acetylcholine, histamine, and antigen challenge was unaffected by nifedipine 10(-4)M. Contraction of HBM by acetylcholine, histamine and grass pollen antigen challenge was significantly reduced by nifedipine 10(-4)M and 10(-6)M. The magnitude of the reduction in contraction to antigen challenge was comparable to the inhibition of acetylcholine and histamine responses. It would appear most likely that nifedipine exerts its effect mainly on bronchial muscle contractility rather than by stabilizing mast cells.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6303164&dopt=Abstract
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