Pharmacokinetics and pharmacodynamics of nifedipine in patients at steady state

Nifedipine Potentiates Susceptibility of Salmonella Typhimurium to Different Classes of Antibiotics

The calcium channel blocker nifedipine induces cellular iron export, thereby limiting the availability of the essential nutrient iron for intracellular pathogens, resulting in bacteriostatic activity. To study if nifedipine may exert a synergistic anti-microbial activity when combined with antibiotics, we used the mouse macrophage cell line RAW267.4, infected with the intracellular bacterium Salmonella Typhimurium, and exposed the cells to varying concentrations of nifedipine and/or ampicillin, azithromycin and ceftriaxone. We observed a significant additive effect of nifedipine in combination with various antibiotics, which was not observed when using Salmonella, with defects in iron uptake. Of interest, increasing intracellular iron levels increased the bacterial resistance to treatment with antibiotics or nifedipine or their combination. We further showed that nifedipine increases the expression of the siderophore-binding peptide lipocalin-2 and promotes iron storage within ferritin, where the metal is less accessible for bacteria. Our data provide evidence for an additive effect of nifedipine with conventional antibiotics against Salmonella, which is partly linked to reduced bacterial access to iron.

Nitric oxide inhibits androgen receptor-mediated collagen production in human gingival fibroblasts

Lin S-J, Lu H-K, Lee H-W, Chen Y-C, Li C-L, Wang L-F. Nitric oxide inhibits androgen receptor-mediated collagen production in human gingival fibroblasts. J Periodont Res 2012; 47: 701-710. © 2012 John Wiley & Sons A/S Background and Objective:  In our previous study, we found that flutamide [an androgen receptor (AR) antagonist] inhibited the up-regulation of collagen induced by interleukin (IL)-1β and/or nifedipine in gingival fibroblasts. The present study attempted to verify the role of nitric oxide (NO) in the IL-1β/nifedipine-AR pathway in gingival overgrowth.

MATERIAL AND METHODS

  Confluent gingival fibroblasts derived from healthy individuals (n = 4) and those with dihydropyridine-induced gingival overgrowth (DIGO) (n = 6) were stimulated for 48 h with IL-1β (10 ng/mL), nifedipine (0.34 μm) or IL-1β + nifedipine. Gene and protein expression were analyzed with real-time RT-PCR and western blot analyses, respectively. Meanwhile, Sircol dye-binding and the Griess reagent were, respectively, used to detect the concentrations of total soluble collagen and nitrite in the medium.

RESULTS

  IL-1β and nifedipine simultaneously up-regulated the expression of the AR and type-I collagen α1 [Colα1(I)] genes and the total collagen concentration in DIGO cells (p < 0.05). IL-1β strongly increased the expression of inducible nitric oxide synthase (iNOS) mRNA and the nitrite concentration in both healthy and DIGO cells (p < 0.05). However, co-administration of IL-1β and nifedipine largely abrogated the expression of iNOS mRNA and the nitrite concentration with the same treatment. Spearman's correlation coefficients revealed a positive correlation between the AR and total collagen (p < 0.001), but they both showed a negative correlation with iNOS expression and the NO concentration (p < 0.001). The iNOS inhibitor, 1400W, enhanced IL-1β-induced AR expression; furthermore, the NO donor, NONOate, diminished the expression of the AR to a similar extent in gingival fibroblasts derived from both healthy patients and DIGO patients (p < 0.05).

CONCLUSION

  IL-1β-induced NO attenuated AR-mediated collagen production in human gingival fibroblasts. The iNOS/NO system down-regulated the axis of AR/Colα1(I) mRNA expression and the production of AR/total collagen proteins by DIGO cells.

Comparative pharmacokinetics of two nifedipine products in capsule form following single oral administration in healthy volunteers

The pharmacokinetic parameters (AUC, Cmax, Tmax, and t1/2) of nifedipine following single oral administration of a 10 mg capsule of test product were compared to those of the same amount of a reference product. The two products in capsule form were administered according to a randomized two-way crossover design in 22 healthy male volunteers. Nifedipine plasma concentrations were determined using a rapid, sensitive and precise high performance liquid chromatography (HPLC) method with ultraviolet (UV) detection at 235 nm. The parametric 90% confidence intervals of the mean value of the ratio [Myogard (test product) /Adalat (reference product)] for pharmacokinetic parameters were 0.90-1.08, 0.80-1.07, and 0.93-1.12 for AUC0-->infinity, Cmax and t1/2, respectively. In each case, values were within the acceptable bioequivalence range of 0.8-1.25. Distribution free point estimate for the difference in expected medians of Tmax of the two products (Myogard-Adalat) was 0.00 h with a 90% confidence interval of 0.00-0.13 which is greater than the accepted bioequivalence of +/- 0.12. The kinetic parameters were comparable to those reported for nifedipine, and no statistically significant differences were found in any of them when comparing the two products by analysis of variance (ANOVA) on log-transformed data. Thus, the two products could be considered bioequivalent regarding absorption rate (Cmax and Tmax), extent of absorption (Cmax and AUC) and elimination (t1/2).

Serum nifedipine concentrations and response of patients with pulmonary hypertension

In patients with primary pulmonary hypertension who respond to nifedipine during acute drug testing, there is a significant linear correlation of serum nifedipine concentration with pulmonary artery pressure and resistance. Although most demonstrate an initial response at readily attainable nifedipine concentrations with conventional dosages, a subset of patients seem to display delayed or incomplete oral absorption; these results may facilitate the clinical use of nifedipine in patients with primary pulmonary hypertension.

Comparative effects of felodipine, nitrendipine and nifedipine in healthy subjects: concentration-effect relationships of racemic drugs and enantiomers

The effects of racemic (rac) felodipine, rac-nitrendipine and nifedipine (all 20 mg solution p.o.) on non-invasively measured blood pressure and heart rate were investigated in a randomised, double-blind, cross-over study in 12 normotensive, young, healthy males. Compared to baseline values, heart rate increased more after rac-felodipine treatment (+47% at maximum) than rac-nitrendipine (+40%) and nifedipine (+38%); only small and variable changes in blood pressure were observed with any of the drugs. The baseline-corrected area under the heart rate-time curve up to 4 h after the administration of rac-felodipine was 197% and 180% larger than after nifedipine and rac-nitrendipine treatment, respectively. The effects on heart rate could be fitted individually to a sigmoidal Emax-model without hysteresis for all drugs under investigation. The relative potencies of the unbound drugs for their indirect effects on heart rate were 1:7:43 for nifedipine, rac-nitrendipine and rac-felodipine, respectively. The active (S)-enantiomers of felodipine and nitrendipine appeared to be 9- and 60-times as potent as nifedipine in this respect, assuming no (inter)activity of the (R)-enantiomers. Individual and mean changes in blood pressure were small, they were not related to plasma concentrations, and did not differ between treatments.

Transcranial Doppler to evaluate the effects of antihypertensive medication on cerebral blood flow velocity

The effect of oral nifedipine on cerebral blood flow velocity was studied in six elderly hypertensive patients using transcranial Doppler. Serial measurements of blood pressure (BP), middle cerebral artery (MCA) flow velocity and nifedipine serum concentrations were obtained over an 8-hour period. The authors found a significant inverse relationship between MCA velocities and nifedipine concentrations, independent of BP changes. These results are consistent with a direct vasodilatory effect of nifedipine on cerebral vessels and support the use of TCD in pharmacodynamic investigations of the cerebral vasculature.

The calcium channel blocker nifedipine attenuates slow excitatory amino acid neurotoxicity

High concentrations of potent N-methyl-D-aspartate (NMDA) agonists can trigger degeneration of cultured mouse cortical neurons after an exposure of only a few minutes; in contrast, selective non-NMDA agonists or low levels of NMDA agonists require exposures of several hours to induce comparable damage. The dihydropyridine calcium channel antagonist nifedipine was used to test whether this slow neurotoxicity is mediated by a calcium influx through voltage-gated channels. Nifedipine had little effect on the widespread neuronal degeneration induced by brief exposure to high concentrations of NMDA but substantially attenuated the neurotoxicity produced by 24-hour exposure to submaximal concentrations of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate, kainate, or quinolinate. Calcium ion influx through dihydropyridine-sensitive, voltage-dependent calcium channels may be an important step in the neuronal injury induced by the prolonged activation of NMDA or non-NMDA glutamate receptors.

The calcium channel blocker nifedipine attenuates slow excitatory amino acid neurotoxicity

High concentrations of potent N-methyl-D-aspartate (NMDA) agonists can trigger degeneration of cultured mouse cortical neurons after an exposure of only a few minutes; in contrast, selective non-NMDA agonists or low levels of NMDA agonists require exposures of several hours to induce comparable damage. The dihydropyridine calcium channel antagonist nifedipine was used to test whether this slow neurotoxicity is mediated by a calcium influx through voltage-gated channels. Nifedipine had little effect on the widespread neuronal degeneration induced by brief exposure to high concentrations of NMDA but substantially attenuated the neurotoxicity produced by 24-hour exposure to submaximal concentrations of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate, kainate, or quinolinate. Calcium ion influx through dihydropyridine-sensitive, voltage-dependent calcium channels may be an important step in the neuronal injury induced by the prolonged activation of NMDA or non-NMDA glutamate receptors.

Effects of cardiovascular disease on pharmacokinetics

The pathophysiologic changes occurring in cardiovascular disease can affect the kinetics of drugs in several different ways. The present review examines these modifications and the underlying mechanisms. The kinetics of specific agents, such as antiarrhythmic, antihypertensive, cardiotonic, and other drugs are considered, and the clinical implications are outlined. The clinician should be aware of these modifications, because they require an adjustment of the dosage regimen. A rational basis for a correct therapeutic choice can be provided by adequate knowledge of these modifications.

Pharmacokinetics of oral nifedipine: relevance of the distribution phase

Pharmacokinetics of oral Nifedipine was studied in 12 Mexican young healthy volunteers, six men and six women, who received a 10 mg capsule. Plasma levels were determined by a nifedipine specific HPLC assay. Experimental data were fitted and pharmacokinetic parameters were calculated using an open two compartment model. No statistically significant difference was detected between men and women, thus both sexes were considered as a single population. Nifedipine plasma levels rose rapidly (ka = 8.46 +/- 1.96 h-1) reaching a maximum concentration of 145 +/- 23 ng/ml in 0.61 +/- 0.07 h. Plasma levels then decayed with a distribution phase (alpha = 1.98 +/- 0.40 h-1, t1/2 alpha = 0.46 +/- 0.06 h) and a terminal elimination phase (beta = 0.17 +/- 0.03 h-1, t1/2 beta = 4.98 +/- 0.55 h). AUC was 384 +/- 41 ng h/ml. Values of AUC and t1/2 beta were higher than those reported by other authors. Differences in the AUC could be due to ethnic origin, environmental factors or nutritional habits. Ten subjects presented plasma concentration-time curves in which the distribution phase was clearly distinguishable, having a ka/alpha relationship higher than 1.5. For the other two subjects, the distribution phase was not apparent and ka/alpha was lower than 1.5. The results show that an adequate characterization of the distribution phase is required if one pretends to use pharmacokinetic data for dosage regimen design.

Influence of nifedipine therapy on indocyanine green and oral propranolol pharmacokinetics

Nine healthy adults were administered indocyanine green (ICG) 0.5 mg.kg-1 IV alone and after the administration of the following oral drugs: nifedipine 10 mg, propranolol 80 mg, propranolol 80 mg and nifedipine 10 mg, and propranolol 80 mg after nifedipine 10 mg every 8 h for 5 days. Heart rate and mean arterial blood pressure (MAP) were also determined. Nifedipine increased ICG clearance by 14% and decreased t1/2 by 26%. Propranolol decreased ICG clearance by 21% and increased t1/2 42%. Nifedipine and propranolol given together increased ICG clearance 63% and decreased t1/2 by 19%. All changes were statistically significant. Propranolol given after multiple doses of nifedipine did not change ICG kinetic parameters. Propranolol Cmax, tmax, oral clearance, and t1/2 did not change after nifedipine therapy. However, partial propranolol AUC values between 0-0.33, 0-0.5, 0-1.0 and 0-1.5 h were significantly larger after single and multiple doses of nifedipine indicating higher propranolol concentrations during the absorption phase. Heart rate and MAP did not change after nifedipine treatment. Similar declines in heart rate and MAP occurred after propranolol alone and propranolol after single and multiple doses of nifedipine.