title: A pharmacodynamic model of the effects of controlled-onset extended-release verapamil on 24-hour ambulatory blood pressure.
abstract: OBJECTIVE
  To formulate and evaluate a pharmacodynamic model that characterizes the effects of S-verapamil on the circadian 24-hour ambulatory blood pressure (ABP).
  
  
  METHODS
  ABP was recorded in 19 hypertensive patients off drug, and following administration of the targeted dose of COER-V given once daily for at least 30 days. Blood samples were collected after the last dose for determination of the pharmacokinetic of S-verapamil. ABP vs. time was analyzed using a cosinor function, and the effects of S-verapamil on ABP were fitted using the pharmacodynamic model.
  
  
  RESULTS
  COER-V decreased average systolic and diastolic blood pressures (mesors): baseline, 142 +/- 10 and 90 +/- 7; treated, 132 +/- 8.8 and 83 +/- 6.6 mmHg, respectively (p < 0.001). COER-V had no effect on the amplitude, cycle or the time shift (acrophase). The mean +/- SD time to peak and maximal S-verapamil concentrations were 9.5 +/- 1.2 hours and 46.4 +/- 35.8 ng/ml, respectively. Model estimates of the maximal inhibited systolic (Emax S), diastolic. (Emax D) pressures and C50 were 101 +/- 14 mmHg, 61 +/- 9.9 mmHg and 32.9 +/- 22.8 ng/ml, respectively. The model fit of the data was satisfactory and parameter estimates were precise.
  
  
  CONCLUSIONS
  The model may be useful to characterize the relationship between plasma concentrations of verapamil and the antihypertensive effects of the drug and may be suitable for characterizing the effect of drugs on biological functions displaying oscillatory behavior.
authors.affiliation: Center for Clinical Pediatric Pharmacology & Pharmacogenetics, Nemours Children's Clinic, 807 Nira Street, Jacksonville, FL 32207, USA. Jlima@nemours.org
authors.forename: J J
authors.initials: JJ
authors.lastname: Lima
authors.forename: B Nhi
authors.initials: BN
authors.lastname: Beasley
authors.forename: R B
authors.initials: RB
authors.lastname: Parker
authors.forename: J A
authors.initials: JA
authors.lastname: Johnson
mesh_terms: D000959:Antihypertensive Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D018660:Blood Pressure Monitoring, Ambulatory; D002940:Circadian Rhythm; D003692:Delayed-Action Preparations; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D008954:Models, Biological; D016896:Treatment Outcome; D014700:Verapamil / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D000959:Antihypertensive Agents; D003692:Delayed-Action Preparations; D014700:Verapamil