| 1. |
- Eriksson, Johan, et al.
(författare)
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3,4,5,6-Tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O, 2,4,5,6-tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O and 2,3,5,6-tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O
- 2004
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Annan publikation (populärvet., debatt m.m.)
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| 2. |
- Äbelö, Angela, et al.
(författare)
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Pharmacodynamic modelling of reversible gastric acid pump inhibition in dog and man
- 2001
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Ingår i: European Journal of Pharmaceutical Sciences. - 0928-0987 .- 1879-0720. ; 14:4, s. 339-346
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Tidskriftsartikel (refereegranskat)abstract
- H 335/25, a 4-amino quinoline, belongs to a new class of reversible gastric acid pump inhibitors. A potential advantage of such drugs over the irreversible proton pump inhibitors (PPIs) is better control over the effect-time profile. Dose escalation studies were performed to characterize the effect on acid secretion in dogs (n=24) and healthy male subjects (n=12). The effect-time profile was delayed compared to the concentration-time profile. A model-based approach, using non-linear mixed effects modelling, was applied to quantify and elucidate the mechanism for the delayed effect. Three different models were investigated: (1) a slow equilibration preceding the formation of drug-enzyme complex, modelled by an effect-compartment, (2) a slow equilibration between free drug, free enzyme and drug-enzyme complex, described by a kinetic binding model, and (3) a delay between enzyme inhibition and the measured response, described by an indirect response model. Model 2 was shown to be superior to models 1 and 3, for both dog and human data. The dissociation rate constant, k(off), was estimated to be 0.85 and 0.88 h and the calculated equilibration constant, K(d), was 160 and 250 nM in dog and man, respectively. Simulations of the predicted time-course of the effect beyond the 4-5-h observation period was similar for the three models.
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| 3. |
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| 4. |
- Äbelö, Angela, et al.
(författare)
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A turnover model of irreversible inhibition of gastric acid secretion by omeprazole in the dog
- 2000
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Ingår i: Journal of Pharmacology and Experimental Therapeutics. - 0022-3565 .- 1521-0103. ; 295:2, s. 662-669
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Tidskriftsartikel (refereegranskat)abstract
- A turnover model for irreversible inhibition of gastric acid secretion by omeprazole in gastric fistula dogs was developed using data from studies with both short- and long-term measurement periods. In the short-term experiments, after stimulation of acid secretion with histamine, the dogs were infused i.v. with omeprazole and acid secretion was measured for 5 h. Dose and infusion times were varied to produce different concentration-time profiles and schedule dependence in the inhibitory effect of omeprazole was observed. In the long-term experiments, dogs were given single intraduodenal doses, which inhibited the acid secretion for several days. Combining the short-term and long-term data allowed the observation of a biphasic recovery of acid secretion that was described by the turnover model. Second order association rate constants (k(ome)) for the covalent binding of omeprazole to H(+),K(+)-ATPase were estimated to 11 and 3.0 l/micromol/h for the i.v. and intraduodenal experiments, respectively. The apparent turnover rate constant of the enzyme (k(out)) was 0.013 h(-1) and the corresponding half-life of inhibition of acid secretory capacity was 54 h. The potency, calculated as k(out) over k(ome), was 4.3 and 1.2 nM for the intraduodenal and i.v. doses, respectively. Allometric scaling of the model resulted in trustworthy predictions for observations previously done in humans. The model predicted a good correlation between maximal inhibitory effect and exposure (area under the plasma concentration curve). The time dependence in this relation was also predicted by the model.
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| 5. |
- Äbelö, Angela, et al.
(författare)
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Gastric acid secretion in the dog : a mechanism-based pharmacodynamic model for histamine stimulation and irreversible inhibition by omeprazole
- 2002
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Ingår i: Journal of Pharmacokinetics and Pharmacodynamics. - 1567-567X .- 1573-8744. ; 29:4, s. 365-382
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Tidskriftsartikel (refereegranskat)abstract
- A mechanism-based pharmacodynamic model was used to describe the inhibitory effect by omeprazole on gastric acid secretion measured after histamine stimulation in the dog. The model identifies parameters that are related to the physiological system, the histamine stimulation, and the irreversible effect of omeprazole on the H+, K(+)-ATPase enzyme. Four different experiments with omeprazole (Exps. 1-4) and two placebo experiments were performed in each of the four Heidenhain pouch dogs used. For placebo and experiments 1-3, saline or omeprazole 0.81 mumol/kg was infused during 3 hr with measurements of histamine-stimulated gastric acid secretion in two periods of 3.5-6.5 hr, one period starting just before the omeprazole infusion and a second later period up to 29 hr post infusion. In experiment 4, 0.18 mumol/kg of omeprazole was infused for 22.5 min and gastric juice was collected for 5 hr post infusion. The response data was well described by the model. Similar parameter estimates were obtained by three different analysis methods; naïve pooling, two-stage method and nonlinear mixed effects modeling. The elimination rate constant for the H+, K(+)-ATPase enzyme, kout, was estimated to be 0.040 hr-1, corresponding to a half-life of about 17 hr. This rate constant determines the duration of omeprazole inhibition after long-term exposure. For short-term omeprazole exposure the duration is determined by the rate constant for transfer of enzymes from active to resting state, estimated to be 1.88 hr-1. The second-order rate constant for histamine stimulation was estimated to be 0.064 hr-1 per histamine concentration unit and the maximum acid secretion was estimated to be 5.0 mmol H+/30 min. The second-order rate constant for the irreversible binding of omeprazole to H+, K(+)-ATPase, kome, was estimated to be 2.39 L/mumol.hr. By modeling the histamine-induced baseline response simultaneously with active treatment, predictions of the response are possible not only following different dosing regimens of omeprazole, but also following different degrees of histamine stimulation.
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