Drugs online research references
J Clin Pharmacol. 1989 Feb;29(2):107-11.
Hemodynamic and endocrine effects of acute and chronic administration of nifedipine.
Parent R, Chiasson JL, Larochelle P.
Clinical Research Institute of Montreal, Quebec, Canada.
Although it is well known that calcium channel blockers can influence contraction of vascular smooth muscle, there is less knowledge on its effect on excitation contraction coupling in the endocrine glands and more specifically on insulin and glucagon release. In this study, nifedipine was administered in doses of 40 to 80 mg/day to 14 patients with essential hypertension, and its hemodynamic effects were evaluated by non-invasive methods, and its effect on glucose metabolism by an arginine infusion test. Nifedipine produced a significant reduction in systolic and diastolic blood pressure, both after the first dose (30/12 mm Hg) and after 8 weeks of administration (19/12 mm Hg). There were no significant changes in cardiac output (5.1 to 4.9 L/min), muscle (2.4 to 3.2 mL/sec/min) or cutaneous basal flow (9.8 to 8.6 mL/100 mL) as measured non-invasively by echocardiogram and by plethysmography. Insulin and glucagon release were evaluated by the arginine infusion test. Nifedipine produced a tendency towards an increase in glucagon release and a reduction in insulin release although these changes did not reach statistical significance. In this group of patients, nifedipine produced a significant reduction in systolic and diastolic pressure, but no significant changes in insulin or glucagon plasma levels.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2654199&dopt=Abstract
Drugs Exp Clin Res. 1985;11(9):645-51.
An investigation into the effects of nifedipine and nimodipine on platelet function and vascular prostacyclin synthesis.
Jeremy JY, Barradas MA, Mikhailidis DP, Dandona P.
Department of Chemical Pathology and Human Metabolism, Royal Free Hospital, London, UK.
The effect of two calcium-channel blockers (nifedipine; nimodipine) on in vitro platelet function and prostacyclin (PGI2) synthesis was investigated. Platelet aggregation and thromboxane A2 release in platelet-rich plasma were inhibited by both drugs, but the effective concentrations (20 mg/l) were considerably higher than the reported therapeutic levels of the drugs (60 micrograms/l). Platelet impedance aggregometry (PIA) in whole blood was a more sensitive (4-fold) index of the effect of nifedipine on platelets, but inhibitory concentrations of the drug were still considerably higher (5 mg/l) than therapeutic concentrations. Neither nifedipine nor nimodipine had any effect on PGI2 synthesis, which was assessed in terms of conversion of arachidonic acid to PGI2 (in rat aortic and human umbilical tissue) and spontaneous release of PGI2 from rat aortae following in vitro incubations or in vivo administration of nifedipine. The mechanism responsible for the reported inhibition of platelet function following administration of nifedipine remains unclear, but does not appear to involve acute direct effects on platelets or vascular PGI2 production. The authors' PIA findings also indicate that: (a) PIA may be a more sensitive method than conventional (PRP) aggregometry to demonstrate platelet antiaggregatory effects of drugs; and (b) erythrocytes and leucocytes may be involved in the mechanism underlying the antiaggregatory effect of nifedipine.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3939725&dopt=Abstract
Am J Obstet Gynecol. 1985 Apr 15;151(8):1134-40.
Tocolytic and hemodynamic effects of nifedipine in the ewe.
Golichowski AM, Hathaway DR, Fineberg N, Peleg D.
The ability of the calcium antagonist nifedipine to inhibit uterine contractions during labor and in the postpartum period was measured in the ewe. The hemodynamic effects of tocolytic doses of this drug were measured and compared with the hemodynamic effects of equivalent doses of ritodrine. Intravenous nifedipine was found to be a potent tocolytic agent that completely inhibited uterine activity even in advanced labor when administered at infusion rates that resulted in only mild hemodynamic effects. At tocolytically similar infusion rates nifedipine produced significantly less increase in maternal heart rate than did ritodrine.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3985070&dopt=Abstract
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