title: Application of pharmacodynamic modeling for designing time-variant dosing regimens to overcome nitroglycerin tolerance in experimental heart failure.
abstract: OBJECTIVE
  Prolonged continuous administration of nitroglycerin (NTG) leads to hemodynamic tolerance. We used a previously developed pharmacokinetic-pharmacodynamic (PK/PD) model of NTG tolerance in experimental heart failure to test whether dosage regimens, designed from this model, may allow avoidance of tolerance development upon continuous NTG infusion.
  
  
  METHODS
  Simulation experiments (using ADAPT II) were performed to evolve a time-variant infusion regimen that would theoretically provide sustained hemodynamic effect (30% reduction in left ventricular end-diastolic pressure, LVEDP) throughout 10 hours of drug dosing. A computer controlled infusion pump was utilized to deliver this time-variant input. Infusion experiments were then conducted in CHF rats to challenge the predictability of the applied PK/PD model.
  
  
  RESULTS
  Simulations showed that exponentially increasing input functions provided more sustained LVEDP effects when compared to linear or hyperbolic input functions delivering the same total NTG dose. A computer-selected infusion regimen of 6.56e0.00156 x minutes micrograms/min was anticipated to provide the desired hemodynamic profile in our animal model. Experiments conducted in rats with congestive heart failure (n = 4) confirmed the prediction of sustained hemodynamic effect without tolerance (28 +/- 4% reduction in LVEDP at 10 hrs).
  
  
  CONCLUSIONS
  These findings support the utility of our PK/PD model of NTG tolerance in predicting NTG action, and serve as an example of therapeutic optimization through PK/PD considerations.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, State University of New York, Buffalo 14260, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Bauer
authors.forename: J P
authors.initials: JP
authors.lastname: Balthasar
authors.forename: H L
authors.initials: HL
authors.lastname: Fung
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D016503:Drug Delivery Systems; D015195:Drug Design; D004361:Drug Tolerance; D006333:Heart Failure / Q000188:drug therapy*; D008954:Models, Biological; D005996:Nitroglycerin / Q000493:pharmacokinetics*; D051381:Rats; D013997:Time Factors; D014665:Vasodilator Agents / Q000493:pharmacokinetics*
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin