Drugs online research references
Nippon Yakurigaku Zasshi. 1986 Dec;88(6):433-41.
[Alpha-adrenoceptor blocking action of terazosin]
[Article in Japanese]
Hanazuka M, Horii D, Mizogami S.
alpha-Adrenoceptor blocking activities and vascular relaxation activities of terazosin, a new antihypertensive agent, were studied. Terazosin had no effect on Ba2+, serotonin, angiotensin II and Ca2+ induced contractions in the isolated rat aorta. Terazosin competitively inhibited norepinephrine (NE) and phenylephrine (PE) induced contractions of the isolated rat aorta, and their pA2 values were 9.28 and 8.74, respectively. The potency of terazosin in the NE induced contraction was about 0.11, 8 and 176 times more than prazosin, phentolamine and yohimbine, respectively. The potency of terazosin in the PE induced contraction was about 0.09, 6 and 60 times more than prazosin, phentolamine and yohimbine. Terazosin (i.v.) competitively inhibited the PE induced pressor response. The "pA2" values of postsynaptic alpha-adrenoceptor blocking activity was 5.22, and its potency was about 0.05, 5 and 62.5 times more than prazosin, phentolamine and yohimbine, respectively. Terazosin (0.3 mg/kg, i.v. or less) did not show any significant effect on clonidine induced bradycardia during electrical stimulation of cardiac sympathetic nerve, whereas prazosin (0.3 mg/kg), phentolamine (0.1 mg/kg) and yohimbine (0.1 mg/kg) antagonized the effect of clonidine by 37%, 80.6% and 63.3%, respectively. Terazosin, 0.3 and 1 mg/kg, p.o., antagonized the PE (3 micrograms/kg, i.v.) induced pressor response in conscious unrestrained rats. This effect lasted for 8 hr in the case of 0.3 mg/kg and lasted for 12 hr in the case of 1 mg/kg. Thus, it is strong suggested that the antihypertensive effect of terazosin is based on the postsynaptic alpha-adrenoceptor blocking action.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2881853&dopt=Abstract
J Toxicol Sci. 1987 Feb;12 Suppl 1:35-47.
[Antigenicity study of terazosin]
[Article in Japanese]
Hasegawa T, Takahashi K.
Antigenicity of terazosin was studied in the experimental animals and the following results were obtained. Terazosin was shown to be non-immunogenic in guinea-pigs and mice when immunized alone or with mixture of terazosin and protein as immunogen. Protein-conjugate of terazosin induced responses of hapten specific antibody when guinea pigs and mice were immunized. However, terazosin alone was shown to be not capable of eliciting any allergic responses. In conclusion, terazosin lacks immunogenicity and eliciting antigenicity in these experimental conditions and this suggests that drug allergic response would either not occur or be minimal, if any, when terazosin is administered clinically.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2883325&dopt=Abstract
Naunyn Schmiedebergs Arch Pharmacol. 1987 Jan;335(1):44-9.
Pharmacological characterization of the postsynaptic alpha-adrenoceptors in isolated canine mesenteric arteries and veins.
Itoh H, Kohli JD, Rajfer SI.
This investigation was undertaken to characterize the postsynaptic alpha-adrenoceptors in isolated canine mesenteric arterial and venous preparations. Contractile responses to cumulative additions of phenylephrine (selective alpha 1-adrenoceptor agonist), UK-14,304 (selective alpha 2-adrenoceptor agonist), noradrenaline (non-selective alpha-adrenoceptor agonist), and dopamine (non-selective alpha-adrenoceptor agonist) were measured in the presence and absence of rauwolscine, a selective alpha 2-antagonist, and terazosin, a selective alpha 1-antagonist. Phenylephrine was a more potent agonist in the mesenteric artery than in the mesenteric vein; UK-14,304 exhibited the opposite profile of activity. Terazosin was a more potent antagonist than rauwolscine against each of the agonists, except dopamine, in the mesenteric artery but rauwolscine was more potent than terazosin in the vein. Terazosin and rauwolscine were equipotent in inhibiting the contractile responses to dopamine in the artery while rauwolscine was more potent than terazosin in the vein. The pA2 values measured in both vessels failed, however, to demonstrate a high selectivity for either alpha-adrenoceptor antagonist. These results suggest that the alpha-adrenoceptors in the canine mesenteric artery and vein exhibit pharmacological characteristic typical of both alpha 1- and alpha 2-adrenoceptor subtypes.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2883585&dopt=Abstract
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