SD-3211, a novel benzothiazine calcium antagonist, alone and in combination with a beta-adrenoceptor antagonist, produces antihypertensive effects without affecting heart rate and atrioventricular conduction in conscious renal hypertensive dogs.
We compared the effects of SD-3211, a novel calcium antagonist, on blood pressure, heart rate, and atrioventricular conduction with those of diltiazem using conscious renal hypertensive dogs (one-kidney, one-clip type). We also examined the combined effects of these calcium antagonists with a beta-adrenoceptor antagonist, propranolol, on these variables. Oral administration of SD-3211 (1.25, 2.5, and 5 mg/kg) resulted in a dose-dependent decrease in blood pressure without affecting heart rate. SD-3211 at all three doses significantly decreased systolic blood pressure. At 2.5 and 5 mg/kg the compound elicited significant decreases in mean blood pressure and diastolic blood pressure. Hypotension obtained with the highest dose of SD-3211 lasted for at least 9 h. No significant alteration in PR interval was observed in electrocardiograms after administration of SD-3211. Diltiazem, given orally at doses of 2.5 and 5 mg/kg but not 1.25 mg/kg, produced significant hypotension with little change in heart rate. The duration of hypotension induced by the highest dose of diltiazem was only 3 h. Diltiazem prolonged PR interval in a dose-dependent manner, causing second-degree atrioventricular block in some dogs. Combined administration of SD-3211 or diltiazem (2.5 mg/kg) with propranolol (30 mg/kg) resulted in enhanced hypotension with no alteration in heart rate. SD-3211 plus propranolol had little effect on the PR interval, whereas diltiazem plus propranolol caused a markedly enhanced prolongation. These results indicate that SD-3211 is an antihypertensive agent with long-lasting action and little effect on heart rate and atrioventricular conduction and, when administered alone or in combination with propranolol, may be useful in the treatment of hypertension.
Kageyama
M
M
Central Research Laboratories, Santen Pharmaceutical Co., Ltd., Osaka, Japan.
Nishimura
K
K
Takada
T
T
Miyawaki
N
N
Yamauchi
H
H
D000284:Administration, Oral; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology; D001283:Atrioventricular Node / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000008:administration & dosage / Q000494:pharmacology*; D004110:Diltiazem / Q000008:administration & dosage / Q000494:pharmacology; D004285:Dogs; D004359:Drug Therapy, Combination; D004562:Electrocardiography / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006977:Hypertension, Renal / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D011433:Propranolol / Q000494:pharmacology*; D013844:Thiazoles / Q000008:administration & dosage / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D000959:Antihypertensive Agents; D002121:Calcium Channel Blockers; D013844:Thiazoles; D011433:Propranolol; C064356:sesamodil; D004110:Diltiazem