title: Correlation between verapamil plasma concentration and P-R prolongation in essential hypertension.
abstract: Plasma verapamil concentration was correlated with serial electrocardiographic P-R intervals in patients with essential hypertension receiving immediate-release (80 to 120 mg three times a day) or sustained-release (240 mg daily) verapamil. The mean P-R interval in 22 patients taking placebo and immediate-release verapamil was 0.18 second. The borderline first-degree atrioventricular block of three patients did not change during treatment. Plasma verapamil concentrations of patients with a P-R interval longer than 0.20 second and of those with a P-R interval of 0.20 second or less were 169 +/- 73 ng/mL and 63 +/- 8 ng/mL, respectively. Six patients taking sustained-release verapamil had a maximal mean P-R interval of 0.19 +/- 0.01 second during 24-hour ambulatory electrocardiographic monitoring. P-R intervals were 0.22 second or more in two patients, but they returned to normal by hour 7 for one and by hour 20 for the other patient. In summary, transient P-R prolongation occurred with oral verapamil therapy, but no patient, regardless of baseline P-R interval, developed high-grade atrioventricular block.
authors.affiliation: Division of Hypertension and Internal Medicine, Mayo Clinic, Rochester, MN 55905.
authors.forename: P K
authors.initials: PK
authors.lastname: Zachariah
authors.forename: C
authors.initials: C
authors.lastname: Shub
authors.forename: S G
authors.initials: SG
authors.lastname: Sheps
authors.forename: A
authors.initials: A
authors.lastname: Schirger
authors.forename: M K
authors.initials: MK
authors.lastname: Wolf
authors.forename: C A
authors.initials: CA
authors.lastname: Carlson
mesh_terms: D003692:Delayed-Action Preparations; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D014700:Verapamil / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*
chemical_list: D003692:Delayed-Action Preparations; D014700:Verapamil