Studies on Core-Shell Nanocapsules of Felodipine: In Vitro-In Vivo Evaluations.

The present study aimed for in vitro-in vivo-in silico simulation studies of experimentally designed (32-factorial) Capmul PG-8-cored, Eudragit RSPO-Lutrol F 127 nanocapsules to ferry felodipine using GastroPlus™. The in silico parameter sensitivity analysis for pharmacokinetic parameters was initially assessed to justify the preparation of felodipine-loaded nanocapsules (FLNs) with enhanced solubility to overcome the bioavailability issues of felodipine. The overall integrated desirability ranged between 0.8187 and 0.9488 for three optimized FLNs when analyzed for mean particle size, zeta potential, encapsulation efficiency, and in vitro dissolution parameters. The morphological evaluation (SEM, TEM, and AFM) demonstrated spherical nanoparticles (200-300 nm). Validated LC-MS/MS analysis demonstrated enhanced relative bioavailability (13.37-fold) of optimized FLN as compared to suspension. The simulated regional absorption of the FLN presented significant absorption from the cecum (26.3%) and ascending colon (20.1%) with overall absorption of 67.4% from the GIT tract. Furthermore, in vitro-in vivo correlation demonstrated the Wagner-Nelson method as the preferred model as compared to mechanistic and numerical deconvolution on the basis of least mean absolute prediction error, least standard error of prediction, least mean absolute error, and maximum correlation coefficient (r 2 = 0.920). The study demonstrated enhanced oral absorption of felodipine-loaded nanocapsules, and GastroPlus™ was found to be an efficient simulation tool for in vitro-in vivo-in silico simulations.

Coffee-Antihypertensive Drug Interaction: A Hemodynamic and Pharmacokinetic Study With Felodipine.

OBJECTIVES: A period of abstinence from coffee to permit caffeine elimination appears to enable increased blood pressure on subsequent exposure. We hypothesized that this would offset the antihypertensive effect of the dihydropyridine calcium channel blocker felodipine. METHODS: A randomized, single-dose, crossover study assessed hemodynamic and pharmacokinetic effects following 2 days without coffee and caffeine-containing foods. Consistently brewed black coffee (2×300ml), felodipine maximum recommended dose (10mg), and coffee plus felodipine were tested in middle-aged normotensive subjects. RESULTS: Pretreatment plasma caffeine concentrations were unquantifiable. After coffee, blood pressure changes (mm Hg) averaged over study hours 1-4 were increased for brachial systolic (7.6, P < 0.001) and diastolic (4.9, P < 0.001) and aortic systolic (7.4, P < 0.001), pulse (3.0, P < 0.05) and augmentation (1.4, P < 0.05) relative to baseline. After coffee plus felodipine, they were higher for brachial systolic (4.0, P < 0.05) and diastolic (3.9, P < 0.001) and aortic systolic (4.6, P < 0.05) compared to felodipine alone. The pressor effects of coffee and its modulation by felodipine were variable among individuals. Coffee containing caffeine (127mg) caused maximum pressor effect. Caffeine and felodipine pharmacokinetics were similar for coffee and felodipine given alone or in combination indicating an interaction having a pharmacodynamic basis. Plasma felodipine concentration-diastolic blood pressure reduction relationship shifted with coffee such that doubling the felodipine concentration would eliminate the pressor effect. However, this may increase the risk of adverse drug events particularly during the timeframe without coffee. CONCLUSION: Intermittent coffee ingestion might complicate hypertension diagnosis and management for many individuals.

Evaluation of first-pass cytochrome P4503A (CYP3A) and P-glycoprotein activities using felodipine and hesperetin in combination in Wistar rats and everted rat gut sacs in vitro.

The effects of hesperetin on the pharmacokinetics and the role of P-glycoprotein (P-gp) in the transport of felodipine were investigated in rats and in vitro. Felodipine was administered orally (10 mg/kg) without or with hesperetin (25, 50 and 100 mg/kg) to rats for 15 consecutive days. Blood samples were collected at different time intervals on 1(st) day in single dose pharmacokinetic study (SDS) and on 15(th) day in multiple dose pharmacokinetic study (MDS). The area under the plasma concentration-time curve (AUC0-∞ ) and the peak plasma concentration (Cmax ) of felodipine were dose-dependently increased in SDS and MDS with hesperetin compared to control ( p < 0.001). The half-life (t1/2 ) and mean residence time was longer than the control group in both studies. The role of P-gp determined using everted rat gut sacs in vitro by incubating felodipine with or without hesperetin and verapamil (typical P-gp and CYP3A4 inhibitor). The in vitro experiments revealed that the verapamil and hesperetin increased the intestinal absorption of felodipine (p < 0.01). Concurrent use of hesperetin dramatically altered the pharmacokinetics of felodipine leading to an increase in systemic exposure. The likely mechanism is inhibition of CYP3A4-mediated first-pass metabolism and P-gp in the intestine and the liver.

Evaluation of peppermint oil and ascorbyl palmitate as inhibitors of cytochrome P4503A4 activity in vitro and in vivo.

OBJECTIVES: Our study was designed to determine the effect of peppermint oil and ascorbyl palmitate on cytochrome P4503A4 (CYP3A4) activity in vitro and oral bioavailability of felodipine in humans. METHODS: Reversible and mechanism-based inhibitions of nifedipine oxidation were studied in human liver microsomes. The oral pharmacokinetics of felodipine and its dehydrofelodipine metabolite were determined in 12 healthy volunteers after administration of felodipine, 10-mg extended-release tablet, with grapefruit juice (300 mL), peppermint oil (600 mg), ascorbyl palmitate (500 mg), or water in a randomized 4-way crossover study. RESULTS: Peppermint oil (inhibition constant [K(i)] = 35.9 +/- 3.3 microg/mL, mean +/- SEM) and 2 constituents, menthol (K(i) = 87.0 +/- 7.0 micromol/L), and menthyl acetate (K(i) = 124.0 +/- 7.0 micromol/L), produced reversible inhibition of nifedipine oxidation. Ascorbyl palmitate was more potent (K(i) = 12.3 +/- 0.5 micromol/L). None of these substances were mechanism-based inhibitors. Grapefruit juice and peppermint oil increased the area under the curve (AUC) values of felodipine to 173% (range, 94%-280%; P <.01) and 140% (range, 77%-262%; P <.05), respectively, of those with water. They augmented the peak plasma concentration (C(max)) of felodipine and the AUC and C(max) of dehydrofelodipine but did not alter the half-life (t(1/2)) of either substance. Grapefruit juice decreased the dehydrofelodipine/felodipine AUC ratio, but peppermint oil did not. Ascorbyl palmitate did not change the pharmacokinetics of felodipine or dehydrofelodipine compared with water. CONCLUSIONS: Peppermint oil, menthol, menthyl acetate, and ascorbyl palmitate were moderately potent reversible inhibitors of in vitro CYP3A4 activity. Grapefruit juice increased the oral bioavailability of felodipine by inhibition of CYP3A4-mediated presystemic drug metabolism. Peppermint oil may also have acted by this mechanism. However, this requires further investigation. Ascorbyl palmitate did not inhibit CYP3A4 activity in vivo.

Felodipine (once daily) versus nifedipine (four times daily) for Prinzmetal's angina pectoris.

In 30 consecutive patients with Prinzmetal's angina pectoris, the antiischemic effect of felodipine, a new long-acting vasoselective calcium antagonist, administered at doses of 10 and 20 mg once daily was compared with that of the well-established therapeutic regimen with nifedipine administered at a dose of 20 mg 4 times daily. Twenty-four-hour Holter monitoring was performed during a 2-day placebo run-in and at the end of each of 3 consecutive 6-day periods during which the 3 active treatments were administered in randomized sequence. Three patients withdrew, whereas 27 completed the study. The therapeutic regimens tested proved to be similarly effective; primary end points (ischemic episodes recorded by Holter monitoring, and anginal attacks reported on diary cards) occurred in 5 patients (19%) during nifedipine treatment, and in 7 (26%) and 3 (11%) during felodipine treatment with 10 and 20 mg, respectively (p = not significant). The distribution of residual ischemic episodes demonstrated that treatment with felodipine once daily provides 24-hour antiischemic protection. Twenty-six patients were followed up with 20 mg of felodipine once daily for a mean of 6 +/- 5 months, and 21 of them (81%) remained free of symptoms and Holter-recorded ischemic attacks. It is concluded that for Prinzmetal's angina pectoris, 24-hour antiischemic protection may be achieved with administration of felodipine once daily. The availability of a simplified therapeutic approach may constitute a real advantage in terms of patient compliance and improving the quality of life.

Acute renal tubular and hemodynamic effects of the calcium antagonist felodipine in healthy volunteers.

To evaluate the renal tubular effects of felodipine in a low (1.25-mg) and a high (10-mg) dose, lithium clearance was measured and related to renal hemodynamics in 10 healthy volunteers. After felodipine (1.25 mg), mean blood pressure decreased 4 mm Hg and heart rate increased 4 beats per minute. GFR and renal hemodynamics were unaltered. Natriuresis and diuresis increased and lithium clearance and fractional excretion of lithium were unchanged as compared with placebo. Felodipine (10 mg) decreased mean blood pressure 8 mm Hg; heart rate increased 16 beats per minute, and plasma catecholamines were elevated. GFR was unaltered, whereas RBF increased and renal vascular resistance decreased. Natriuresis and diuresis were further increased, and lithium clearance and fractional excretion of lithium were elevated. In conclusion, felodipine in a low dose of 1.25 mg, which did not change renal hemodynamics, had natriuretic and diuretic effects at a predominantly postproximal tubular site, whereas a high dose of 10 mg, which increased RBF and decreased renal vascular resistance, had additional natriuretic and diuretic effects in the proximal tubule.

Felodipine in the treatment of patients with severe hypertension and impaired renal function.

Twenty-three patients with severe hypertension and impaired renal function were included in an open study of the efficacy and tolerance of felodipine treatment over 6 months. All patients were previously treated with a diuretic, a beta blocker, and a vasodilator, and eight of them also received an ACE inhibitor. At the start of felodipine treatment the previously used vasodilator was withdrawn. In nine patients the concomitant antihypertensive treatment was reduced during the study. The glomerular filtration rate (GFR), as 51Cr EDTA clearance, was determined before and at the end of the study. The blood pressure (BP) and heart rate (HR) were recorded at all clinical visits in the morning 12 hours after the evening dose of felodipine and 2 hours after the morning dose. Plasma concentrations of felodipine were measured at every visit before the morning dose and 2 hours after dose. The BP was reduced after felodipine was substituted for the previously used vasodilator. A significant additional anti-hypertensive effect was recorded 2 hours after the dose and amounted to -37 +/- 22/-15 +/- 12 mmHg (p = 0.0001/p = 0.0002) at 6 months. The effect measured 12 hours after the dose was less pronounced and was -11 +/- 28/-6 +/- 10 mmHg (p = 0.15/p = 0.03). Mean GFR was unchanged during the study, 38 +/- 19 versus 38 +/- 19 ml/min (n = 16). There was a sixfold interindividual variation in the trough plasma concentrations at steady state at the same drug dosage. Higher plasma concentrations seemed to be required to achieve the same antihypertensive effects as in patients with less severe hypertension and normal renal function.(ABSTRACT TRUNCATED AT 250 WORDS)