title: The pharmacokinetics of extended-release formulations of calcium antagonists and of amlodipine in subjects with different gastrointestinal transit times.
abstract: The influence of gastrointestinal (GI) transit times on the pharmacokinetics (PK) of three calcium channel blockers (CCBs), recommended for once-daily dosing, was investigated. In a three-way crossover design, the single-dose PK of a controlled-delivery formulation of 240 mg diltiazem (DIL), an extended-release formulation of 10 mg felodipine (FEL), and 5 mg amlodipine (AML) were compared in two groups of healthy subjects, with either slow (> 35 h) or rapid (< 15 h) GI transit, as assessed by the metal detector method (EAS II). GI transit significantly affected the PK of DIL. Mean PK parameters in the rapid versus slow transit group were the following: trough levels (C24 h): 22.8 +/- 8.3 versus 49.5 +/- 35.7 ng/ml, p < 0.05; AUC 1134.4 +/- 512.7 versus 1704.7 +/- 1185.6 hng/ml, p < 0.05 (one-sided). Neither AUC nor trough levels of FEL and AML were significantly influenced by transit times, nor was Cmax after any of the three treatments. Variations in PK parameters, as indicated by coefficients of variation, were about twofold higher for both DIL and FEL, compared to AML. Variations in mean residence times were significantly lower for AML compared to DIL and FEL (7% vs. 30% and 17%, p < 0.001 and p < 0.002, respectively). Peak-to-trough ratios (Cmax/C24 h mean) were 1.8 +/- 0.9 for DIL, 7.6 +/- 3.5 for FEL, and 1.7 +/- 0.2 for AML. In conclusion, the predictability of pharmacokinetic behavior both in conditions of rapid or slow GI transit is optimized in drugs with intrinsically slow elimination such as amlodipine. The pharmacokinetics of the CCBs with formulation-based once-a-day characteristics are sensitive to GI transit if these processes are rapid enough to interfere with the formulation-specific release profile.
authors.affiliation: Department of Pharmacology, Pfizer R + D Laboratories, Illertissen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Zimmermann
authors.forename: H
authors.initials: H
authors.lastname: Laufen
authors.forename: R
authors.initials: R
authors.lastname: Yeates
authors.forename: F
authors.initials: F
authors.lastname: Scharpf
authors.forename: K D
authors.initials: KD
authors.lastname: Riedel
authors.forename: T
authors.initials: T
authors.lastname: Schumacher
mesh_terms: D000328:Adult; D017311:Amlodipine / Q000009:adverse effects / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001682:Biological Availability; D002121:Calcium Channel Blockers / Q000009:adverse effects / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D003692:Delayed-Action Preparations; D004110:Diltiazem / Q000009:adverse effects / Q000493:pharmacokinetics; D015736:Felodipine / Q000008:administration & dosage / Q000493:pharmacokinetics; D005260:Female; D005767:Gastrointestinal Diseases / Q000139:chemically induced; D005772:Gastrointestinal Transit / Q000502:physiology*; D006261:Headache / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D002121:Calcium Channel Blockers; D003692:Delayed-Action Preparations; D017311:Amlodipine; D004110:Diltiazem; D015736:Felodipine