Stealth Amphotericin B nanoparticles for oral drug delivery: In vitro optimization

Purpose

Amphotericin B (AmB) is an effective anti-fungal and anti-leishmanial agent. However, AmB has low oral bioavailability (0.3%) and adverse effects (e.g., nephrotoxicity). The objectives of this study were to improve the oral bioavailability by entrapping AmB in pegylated (PEG) poly lactide co glycolide copolymer (PLGA–PEG) nanoparticles (NPs). The feasibility of different surfactants and stabilizers on the mean particle size (MPS) and entrapment efficiency were also investigated.

Materials and methods

NPs of AmB were prepared by a modified emulsification diffusion method employing a vitamin E derivative as a stabilizer. Physicochemical properties and particle size characterization were evaluated using Fourier Transform Infra-Red spectroscopy (FTIR), differential scanning calorimetry, scanning electron microscopy and transmission electron microscopy. Moreover, in vitro dissolution profiles were performed for all formulated AmB NPs.

Results

MPS of the prepared spherical particles of AmB ranged from 26.4 ± 2.9 to 1068 ± 489.8 nm. An increased stirring rate favored AmB NPs with a smaller MPS. There was a significant reduction in MPS, drug content and drug release, when AmB NPs were prepared using the diblock polymer PLGA–PEG with 15% PEG. Addition of three emulsifying agents poly vinyl pyrrolidone (PVP), Vitamin E (TPGS) and pluronic F-68 to AmB formulations led to a significant reduction in particle size and increase in drug entrapment efficiency (DEE) compared to addition of PVP alone. FTIR spectroscopy demonstrated a successful loading of AmB to pegylated PLGA–PEG copolymers. PLGA–PEG copolymer entrapment efficiency of AmB was increased up to 56.7%, with 92.7% drug yield. After a slow initial release, between 20% and 54% of AmB was released in vitro within 24 h phosphate buffer containing 2% sodium deoxycholate and were best fit Korsmeyer–Peppas model. In conclusion, PLGA–PEG diblock copolymer with 15% PEG produced a significant reduction (>70%) in MPS with highest drug content. The percentage of PEG in the copolymer and the surfactant/stabilizer used had a direct effect on AmB release in vitro, entrapment efficiency and MPS. These developed formulations are feasible, effective and improved alternatives to other carriers for oral delivery of AmB.     

Proliposomes for oral delivery of dehydrosilymarin: preparation and evaluation in vitro and in vivo

Aim:

To formulate proliposomes with a polyphase dispersed system composed of soybean phospholipids, cholesterol, isopropyl myristate and sodium cholate to improve the oral bioavailability of dehydrosilymarin, an oxidized form of herbal drug silymarin.

Methods:

Dehydrosilymarin was synthesized from air oxidation of silymarin in the presence of pyridine, and proliposomes were prepared by a film dispersion-freeze drying method. Morphological characterization of proliposomes was observed using a transmission electron microscope. Particle size and encapsulation efficiency of proliposomes were measured. The in vitro release of dehydrosilymarin from suspension and proliposomes was evaluated. The oral bioavailability of dehydrosilymarin suspension and proliposomes was investigated in rabbits.

Results:

The proliposomes prepared under the optimum conditions were spherical and smooth with a mean particle size in the range of 7 to 50 nm. Encapsulation efficiency was 81.59%±0.24%. The in vitro accumulative release percent of dehydrosilymarinloaded proliposomes was stable, which was slow in pH 1.2, and increased continuously in pH 6.8, and finally reached 86.41% at 12 h. After oral administration in rabbits, the relative bioavailability of proliposomes versus suspension in rabbits was 228.85%.

Conclusion:

Proliposomes may be a useful vehicle for oral delivery of dehydrosilymarin, a drug poorly soluble in water.     

16α-Hydroxycleroda-3,13 (14)Z-dien-15,16-olide from Polyalthia longifolia: a safe and orally active antileishmanial agent

Background and purpose:

New antileishmanials from natural products are urgently needed due to the emergence of drug resistance complicated by severe cytotoxic effects. 16α-Hydroxycleroda-3,13 (14)Z-dien-15,16-olide (Compound 1) from Polyalthia longifolia was found to be a potential antileishmanial and non-cytotoxic, as evidenced by long-term survival (>6 months) of treated animals. This prompted us to determine its target and, using molecular modelling, identify the interactions responsible for its specific antileishmanial activity.

Experimental approach:

In vitro activity of compound was assessed using intracellular transgenic green fluorescent protein-stably expressed Leishmania donovani parasites. In vivo activity and survival of animals post-treatment were evaluated in L. donovani-infected hamsters. Known property of clerodane diterpenes as potent human DNA topoisomerase inhibitors led us to evaluate the inhibition of recombinant L. donovani topoisomerase I using relaxation assay. Mode of cell death induced by Compound 1 was assessed by phosphotidylserine exposure post-treatment. Molecular modelling studies were conducted with DNA topoisomerase I to identify the binding interactions responsible for its activity.

Key results:

Bioassay-guided fractionation led to isolation of Compound 1 as a non-cytotoxic, orally active antileishmanial. Compound 1 inhibited recombinant DNA topoisomerase I which, ultimately, induced apoptosis. Molecular docking studies indicated that five strong hydrogen-bonding interactions and hydrophobic interactions of Compound 1 with L. donovani DNA-topoisomerase are responsible for its antileishmanial activity.

Conclusions and implications:

The data reveal Compound 1 is a potent and safe antileishmanial. The study further exploited the structural determinants responsible for its non-cytotoxic and potent activity, to raise the feasibility of specifically targeting the target enzyme responsible for its activity through rational drug design.     

Enhancement of oral bioavailability of the poorly water-soluble drug silybin by sodium cholate/ phospholipid-mixed micelles

Aim:

To evaluate a mixed micellar drug delivery system composed of sodium cholate and phospholipid for oral administration of silybin, a promising hepatoprotectants.

Methods:

The optimum formulation of sodium cholate/phospholipid-mixed micelles containing silybin was obtained based on the study of pseudo-ternary phase diagram. The dissolution of silybin-mixed micelles was investigated. The pharmacokinetic characteristics and bioavailability after oral administration of silybin-mixed micelles and silybin-N-methylglucamine were compared in dogs.

Results:

The mean particle size of prepared mixed micelles was 75.9±4.2 nm. The largest solubility of silybin was found to be 10.0±1.1 mg/mL in the optimum formulation of mixed micelles. The silybin-sodium cholate/phospholipid-mixed micelles showed a very slow release of silybin 17.5% (w/w) within 72 h in phosphate buffer (pH 7.4) and 15.6% (w/w) in HCl solution (pH 1.2). After oral administration to dogs, the relative bioavailability of mixed micelles versus silybin-N-methylglucamine in dogs was 252.0%.

Conclusion:

Sodium cholate/phospholipid-mixed micelles are promising carriers in orally delivery of silybin, considering their capability of enhancing bioavailability and large-scale production.     

Simultaneous oral therapeutic and intravenous 14C‐microdoses to determine the absolute oral bioavailability of saxagliptin and dapagliflozin

Aim

To determine the absolute oral bioavailability (F_p.o.) of saxagliptin and dapagliflozin using simultaneous intravenous ¹⁴C‐microdose/therapeutic oral dosing (i.v.micro + oraltherap).

Methods

The F_p.o. values of saxagliptin and dapagliflozin were determined in healthy subjects (n = 7 and 8, respectively) following the concomitant administration of single i.v. micro doses with unlabelled oraltherap doses. Accelerator mass spectrometry and liquid chromatography‐tandem mass spectrometry were used to quantify the labelled and unlabelled drug, respectively.

Results

The geometric mean point estimates (90% confidence interval) F_p.o. values for saxagliptin and dapagliflozin were 50% (48, 53%) and 78% (73, 83%), respectively. The i.v.micro had similar pharmacokinetics to oraltherap.

Conclusions

Simultaneous i.v.micro + oraltherap dosing is a valuable tool to assess human absolute bioavailability.     

Oral diacetylmorphine (heroin) yields greater morphine bioavailability than oral morphine: bioavailability related to dosage and prior opioid exposure

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Venosclerosis prevents many opioid addicts in heroin substitution programmes from injecting intravenously, which makes consideration of other routes of administration necessary.
• Even high doses of oral diacetylmorphine are completely converted to morphine presystemically.
• Morphine bioavailability in heroin addicts after high-dose oral diacetylmorphine administration is considerably higher than expected based on prior data obtained with relatively low oral diacetylmorphine or morphine doses in healthy subjects or patients receiving treatment for pain (64–72% vs. 20–25%).

WHAT THIS STUDY ADDS

• Morphine influx into systemic circulation is more rapid after oral diacetylmorphine than after oral morphine, resulting in earlier and more than double maximal concentrations.
• In opioid-dependent people, bioavailability of morphine from oral doses of diacetylmorphine is also 37% higher than that of oral morphine.
• Morphine bioavailability is two and 1.5 times higher in chronic users than in opioid-naive subjects after low oral doses of diacetylmorphine or morphine, respectively.
• Oral absorption of morphine from diacetylmorphine is dose dependent, i.e. bioavailability increases with diacetylmorphine dose.

AIMS

In the Swiss heroin substitution trials, patients are treated with self-administered diacetylmorphine (heroin). Intravenous administration is not possible in patients that have venosclerosis. Earlier studies have demonstrated that oral diacetylmorphine may be used, although it is completely converted to morphine presystemically. Morphine bioavailability after high-dose oral diacetylmorphine is considerably higher than would be predicted from low-dose trials. The aim was to investigate whether the unexpectedly high bioavailability is due to a difference in the drug examined, and whether it depends on previous exposure or on dose.

METHODS

Opioid-naive healthy volunteers and dependent patients from the Swiss heroin trials (n = 8 per group) received low doses of intravenous and oral deuterium-labelled morphine and diacetylmorphine, respectively. Patients also received a high oral diacetylmorphine dose.

RESULTS

The maximum plasma concentration (C_max) of morphine was twofold higher after oral diacetylmorphine than after morphine administration in both groups. However, morphine bioavailability was considerably higher in chronic users [diacetylmorphine 45.6% (95% confidence interval 40.0, 51.3), morphine 37.2% (30.1, 44.3)] than in naive subjects [diacetylmorphine 22.9% (16.4, 29.4), morphine 23.9% (16.5, 31.2)] after low oral doses (48.5 µmol) of either diacetylmorphine or morphine. Morphine clearance was similar in both groups. Moreover, oral absorption of morphine from diacetylmorphine was found to be dose dependent, with bioavailability reaching 64.2% (55.3, 73.1) for high diacetylmorphine doses (1601 µmol).

CONCLUSIONS

Oral absorption of opioids is substance-, dose- and patient collective-dependent, suggesting that there may be a saturation of first-pass processes, the exact mechanism of which is not yet understood.     

Sublingual administration of furosemide: new application of an old drug

What is already known about this subject

• Furosemide is an effective diuretic, but its absorption may be too slow to allow oral treatment in certain patients.

What this study adds

• In healthy volunteers, sublingual administration is associated with a higher C_max, a higher bioavailability and a more accentuated initial natriuretic response than oral furosemide. Sublingual administration may offer advantages over oral administration of furosemide in certain clinical situations.

Background

In patients with decompensated heart failure, absorption of orally administered furosemide may be delayed, possibly leading to impaired pharmacodynamic effects. Sublingual administration may represent an alternative in such situations.

Methods

In a crossover study including 11 healthy men, 20 mg furosemide was administered intravenously, orally and sublingually on three different days. Pharmacokinetics and pharmacodynamics were assessed from repeated blood and urine samples.

Results

Compared with oral administration, sublingual administration was associated with 43% higher C_max[difference 215 ng ml⁻¹, 95% confidence interval (CI) 37, 392], a higher urinary recovery (8.9 vs. 7.3 mg, difference 1.6 mg, 95% CI 0.3, 2.9), an 28% higher AUC (difference 328 ng h⁻¹ ml⁻¹, 95% CI 24, 632) and a higher bioavailability of furosemide (59 vs. 47%, difference 12.0%, 95% CI −1.2, 25.2). Sodium excretion was higher after sublingual compared with oral administration (peak excretion rate 1.8 vs. 1.4 mmol min⁻¹, P < 0.05), whereas urine volume did not differ significantly between the two application modes. In comparison, intravenous administration showed the expected more rapid and intense response.

Conclusion

Sublingually administered furosemide tablets differ in certain kinetic and dynamic properties from identical tablets given orally. Sublingual administration of furosemide may offer therapeutic advantages in certain groups of patients.     

Relative bioavailability of terbutaline to the lung following inhalation, using urinary excretion

AIMS

The aim of the study was to determine the relative lung and systemic bioavailability of terbutaline.

METHODS

On separate days healthy volunteers received 500 µg terbutaline study doses either inhaled from a metered dose inhaler or swallowed as a solution with and without oral charcoal. Urine samples were provided at timed intervals post dosing.

RESULTS

Mean (SD) urinary terbutaline 0.5 h post inhalation, in 12 volunteers, with (IC) and without (I) oral charcoal and oral (O) dosing was 7.4 (2.2), 6.5 (2.1) and 0.2 (0.2) µg. I and IC were similar and both significantly greater than O (P < 0.001). Urinary 24 h terbutaline post I was similar to IC + O. The method was linear and reproducible, similar to that of the urinary salbutamol method.

CONCLUSIONS

The urinary salbutamol pharmacokinetic method post inhalation applies to terbutaline. Terbutaline study doses can replace routine salbutamol during these studies when patients are studied.     

Influence of food intake on the bioavailability and efficacy of oral calcitonin

AIMS

To investigate the influence of food intake on the bioavailability and pharmacodynamic effects of salmon calcitonin (sCT).

METHODS

A single-blind, randomized, partly placebo-controlled study was conducted in 36 healthy postmenopausal female volunteers aged 62–74 years. The influence of food intake on oral dosing with 0.8 mg of sCT at 22.00 h was evaluated for a (i) predose meal at 18.00 h, (ii) predose meal at 20.00 h, (iii) predose meal at 21.00 h, (iv) postdose meal at 22.10 h, (v) no meal, and (vi) meal at 20.00 h and placebo at 22.00 h. Study biomarkers were plasma sCT levels and changes in the bone resorption marker CTX-I (C-terminal telopeptide of collagen type I).

RESULTS

The predose meal at 18.00 and 21.00 h significantly decreased relative oral bioavailability of sCT to 26% [95% confidence interval (CI) 0.09, 0.73 and 0.09, 0.75, P= 0.009 and P= 0.01]. The meal consumed 10 min after dosing decreased the oral bioavailability of sCT to 59% (95% CI 0.21, 1.68), although nonsignificant (P= 0.48). This decreased bioavailability led to lower relative suppression of serum CTX-I, with an AUC of the 4-h efficacy response of −91%–×–hours for those receiving a meal at 18.00 h, compared with −238%–×–hours for fasting subjects. The Dunnett-adjusted difference between these two treatment sequences was 147%–×–hours (95% CI 68, 225) (P= 0.0003). The AUC was comparable among fasting subjects and those consuming a meal 10 min after dosing.

CONCLUSIONS

Postprandial dosing may limit the bioavailability of orally administered sCT. Maximal benefit can be achieved by dosing at least 10 min prior to meal time.     

Single and multiple dose intravenous and oral pharmacokinetics of the hedgehog pathway inhibitor vismodegib in healthy female subjects

AIM

Vismodegib has demonstrated clinical activity in patients with advanced basal cell carcinoma. The pharmacokinetics (PK) of vismodegib are non-linear. The objective of this study was to determine whether vismodegib PK change following repeated dosing by administering a tracer intravenous (i.v.) dose of ¹⁴C-vismodegib with single and multiple oral doses.

METHODS

Healthy post menopausal female subjects (n= 6/group) received either a single or daily 150 mg vismodegib oral dose with a ¹⁴C-labelled 10 µg i.v. bolus dose administered 2 h after the single or last oral dose (day 7). Plasma samples were assayed for vismodegib by LC-MS/MS and for ¹⁴C-vismodegib by accelerator mass spectrometry.

RESULTS

Following a single i.v. dose, mean clearance, volume of distribution and absolute bioavailability were 43.4 ml h⁻¹, 16.4 l and 31.8%, respectively. Parallel concentration–time profiles following single oral and i.v. administration of vismodegib indicated elimination rate limited PK. Following i.v. administration at steady-state, mean clearance and volume of distribution were 78.5 ml h⁻¹ and 26.8 l, respectively. Comparison of i.v. PK parameters after single and multiple oral dosing showed similar half-life, increased clearance and volume of distribution (81% and 63% higher, respectively) and decreased bioavailability (77% lower) after repeated dosing. Relative to single dose, the unbound fraction of vismodegib increased 2.4-fold with continuous daily dosing.

CONCLUSION

Vismodegib exhibited a long terminal half-life after oral and i.v. administration, moderate absolute bioavailability and non-linear PK after repeated dosing. Results from this study suggest that the non-linear PK of vismodegib result from two separate, non-linear processes, namely solubility limited absorption and high affinity, saturable plasma protein binding.     

Opposite malaria and pregnancy effect on oral bioavailability of artesunate – a population pharmacokinetic evaluation

Aim

The aim was to compare the pharmacokinetic properties of artesunate and dihydroartemisinin in the same women: i) pregnant with acute uncomplicated malaria on day 1 and 2, ii) pregnant with convalescent malaria on day 7 and iii) in a healthy state 3 months post-partum on day 1, 2 and 7.

Methods

Non-linear mixed-effects modelling was used to compare plasma concentration–time profiles of artesunate and dihydroartemisinin over 7 days of treatment following oral and intravenous artesunate administration to pregnant women with uncomplicated Plasmodium falciparum malaria during their second or third trimesters of pregnancy. The same women were restudied 3 months after delivery when fully recovered. Non-compartmental results of the same study have been published previously.

Results

Twenty pregnant patients on the Thailand-Myanmar border were studied and 15 volunteered to be restudied 3 months post-partum. Malaria and pregnancy had no effect on the pharmacokinetic properties of artesunate or dihydroartemisinin after intravenous artesunate administration. However, malaria and pregnancy had opposite effects on the absorption of orally administered artesunate. Malaria increased the absolute oral bioavailability of artesunate by 87%, presumably by inhibiting first pass effect, whereas pregnancy decreased oral bioavailability by 23%.

Conclusions

The population pharmacokinetic analysis demonstrated opposite effects of malaria and pregnancy on the bioavailability of orally administered artesunate. Lower drug exposures during the second and third trimesters of pregnancy may contribute to lower cure rates and thus the development of drug resistance. Dose optimization studies are required for artesunate containing artemisinin-based combination therapies (ACTs) in later pregnancy.     

Novel gastroretentive sustained-release tablet of tacrolimus based on self-microemulsifying mixture: in vitro evaluation and in vivo bioavailability test

Aim:

To develop a novel gastroretentive drug delivery system based on a self-microemulsifying (SME) lipid mixture for improving the oral absorption of the immunosuppressant tacrolimus.

Methods:

Liquid SME mixture, composed of Cremophor RH40 and monocaprylin glycerate, was blended with polyethylene oxide, chitosan, polyvinylpyrrolidone and mannitol, and then transformed into tablets via granulation, with ethanol as the wetting agent. The tablets were characterized in respect of swelling, bioadhesive and SME properties. In vitro dissolution was conducted using an HCl buffer at pH 1.2. Oral bioavailability of the tablets was examined in fasted beagle dogs.

Results:

The tablet could expand to 13.5 mm in diameter and 15 mm in thickness during the initial 20 min of contact with the HCl buffer at pH 1.2. The bioadhesive strength was as high as 0.98±0.06 N/cm². The SME gastroretentive sustained-release tablets preserved the SME capability of the liquid SME formations under transmission electron microscope. The drug-release curve was fit to the zero-order release model, which was helpful in reducing fluctuations in blood concentration. Compared with the commercially available capsules of tacrolimus, the relative bioavailability of the SME gastroretentive sustained-release tablets was 553.4%±353.8%.

Conclusion:

SME gastroretentive sustained-release tablets can enhance the oral bioavailability of tacrolimus with poor solubility and a narrow absorption window.     

Preparation, characterization and in vivo evaluation of bergenin-phospholipid complex

Aim:

To prepare a bergenin-phospholipid complex (BPC) to increase oral bioavailability of the drug.

Methods:

In order to obtain the acceptable BPC, a spherical symmetric design-response surface methodology was used for process optimization. The influence of reaction medium, temperature, drug concentration and drug-to-phospholipid ratio on the combination percentage and content of bergenin in BPC were evaluated. BPC was then characterized by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), ultra-violet (UV) spectroscopy, fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray powder diffraction. The physicochemical properties such as microscopic shape, particle size, zeta-potential, solubility, crystalline form, and hygroscopicity were tested. The pharmacokinetic characteristics and bioavailability of BPC were investigated after oral administration in rats in comparison to bergenin and the physical mixture (bergenin and phospholipids).

Results:

BPC was successfully prepared under the optimum conditions [temperature=60 °C, drug concentration=80 g/L and drug-to-phospholipids ratio=0.9 (w/w)]. The combination percentage was 100.00%±0.20%, and the content of bergenin in the complex was 45.98%±1.12%. Scanning electron microscopy and transmission electron microscopy of BPC showed spherical particles. The average particle size was 169.2±20.11 nm and the zeta-potential was -21.6±2.4 mV. The solubility of BPC in water and in n-octanol was effectively enhanced. The C_max and AUC_0→∞ of BPC were increased, and the relative bioavailability was significantly increased to 439% of bergenin.

Conclusion:

The BPC is a valuable delivery system to enhance the oral absorption of bergenin.     

Absolute bioavailability of imidafenacin after oral administration to healthy subjects

Aims

To investigate the absolute bioavailability of imidafenacin, a new muscarinic receptor antagonist, a single oral dose of 0.1 mg imidafenacin was compared with an intravenous (i.v.) infusion dose of 0.028 mg of the drug in healthy subjects.

Methods

Fourteen healthy male subjects, aged 21–45 years, received a single oral dose of 0.1 mg imidafenacin or an i.v. infusion dose of 0.028 mg imidafenacin over 15 min at two treatment sessions separated by a 1-week wash-out period. Plasma concentrations of imidafenacin and the major metabolites M-2 and imidafenacin-N-glucuronide (N-Glu) were determined. The urinary excretion of imidafenacin was also evaluated. Analytes in biological samples were measured by liquid chromatography tandem mass spectrometry.

Results

The absolute oral bioavailability of imidafenacin was 57.8% (95% confidence interval 54.1, 61.4) with a total clearance of 29.5 ± 6.3 l h⁻¹. The steady-state volume of distribution was 122 ± 28 l, suggesting that imidafenacin distributes to tissues. Renal clearance after i.v. infusion was 3.44 ± 1.08 l h⁻¹, demonstrating that renal clearance plays only a minor role in the elimination of imidafenacin. The ratio of AUC_t of both M-2 and N-Glu to that of imidafenacin was reduced after i.v. infusion from that seen after oral administration, suggesting that M-2 and N-Glu in plasma after oral administration were generated primarily due to first-pass metabolism. No serious adverse events were reported during the study.

Conclusions

The absolute mean oral bioavailability of imidafenacin was determined to be 57.8%. Imidafenacin was well tolerated following both oral administration and i.v. infusion.

What is already known about this subject

• The absolute bioavailability of imidafenacin in rats and dogs is 5.6% and 36.1%, respectively.
• The pharmacokinetic profiles of imidafenacin after oral administration have been revealed.
• Imidafenacin is primarily metabolized to metabolites by CYP3A4 and UGT1A4.

What this study adds

• The absolute bioavailability of imidafenacin in human is 57.8%.
• The pharmacokinetic profiles of imidafenacin after intravenous administration are revealed.
• The formation of metabolites in the plasma is caused mainly by first-pass effects.

     

Effect of food on the pharmacokinetics of the oral phosphodiesterase 5 inhibitor udenafil for the treatment of erectile dysfunction

AIMS

Udenafil is a cyclic guanosine 3′,5′-monophosphate-specific phosphodiesterase type 5 (PDE5) inhibitor developed for the treatment of erectile dysfunction. The aim was to evaluate the effect of food on the pharmacokinetics of udenafil.

METHODS

An open, randomized, three-way crossover study was conducted. Fifteen healthy male volunteers received a single 200-mg oral dose of udenafil while fasting, after a low-fat meal, and after a high-fat meal separated by 7-day washout periods. Serial blood samples were taken up to 48 h after oral administration.

RESULTS

Under fasting conditions, udenafil was rapidly absorbed and t_max was observed typically 1.5 h after administration. The mean t_max values after a low-fat meal and a high-fat meal were 2.6 and 2.1 h, respectively. The ratios (90% confidence intervals) of the geometric means compared with the fasting condition for C_max and AUC_last were 0.79 (0.70, 0.90) and 0.96 (0.89, 1.03) in the low fat-fed condition, respectively, and 1.01 (0.89, 1.15) and 1.03 (0.96, 1.11), respectively, in the high fat-fed condition.

CONCLUSIONS

The t_max of udenafil was delayed under the fed conditions. However, although the C_max was reduced by approximately 21% in the low fat-fed state, overall bioavailability was not affected when taken with food.     

Metabolic and pharmacokinetic studies of scutellarin in rat plasma, urine, and feces

Aim:

To study the metabolic and pharmacokinetic profile of scutellarin, an active component from the medical plant Erigeron breviscapus (Vant) Hand-Mazz, and to investigate the mechanisms underlying the low bioavailability of scutellarin though oral or intravenous administration in rats.

Methods:

HPLC method was developed for simultaneous detection of scutellarin and scutellarein (the aglycone of scutellarin) in rat plasma, urine and feces. The in vitro metabolic stability study was carried out in rat liver microsomes from different genders.

Results:

After a single oral dose of scutellarin (400 mg/kg), the plasma concentrations of scutellarin and scutellarein in female rats were significantly higher than in male ones. Between the female and male rats, significant differences in AUC, t_max2 and C_max2 for scutellarin were found. The pharmacokinetic parameters of scutellarin in the urine also showed significant gender differences. After a single oral dose of scutellarin (400 mg/kg), the total percentage excretion of scutellarein in male and female rats was 16.5% and 8.61%, respectively. The total percentage excretion of scutellarin and scutellarein in the feces was higher with oral administration than with intravenous administration. The in vitro t_1/2 and CL_int value for scutellarin in male rats was significantly higher than that in female rats.

Conclusion:

The results suggest that a large amount of ingested scutellarin was metabolized into scutellarein in the gastrointestinal tract and then excreted with the feces, leading to the extremely low oral bioavailability of scutellarin. The gender differences of pharmacokinetic parameters of scutellarin and scutellarein are due to the higher CL_int and lower absorption in male rats.     

Population pharmacokinetics and bioavailability of tacrolimus in kidney transplant patients

What is already known about this subject

• In spite of its success in ensuring graft survival, therapeutic use of tacrolimus is complicated by its narrow therapeutic index and wide intra- and interpatient variability.
• Some studies of population pharmacokinetics have already been conducted in liver transplant recipients and in paediatric patients.

What this study adds

• Our work determined population pharmacokinetic parameters, in particular bioavailability, in kidney transplant recipients and the relative importance of factors influencing the disposition of tacrolimus.
• Clearance was modelled and days postoperation and corticosteroids dose were significant covariates.

Aims

The use of tacrolimus is complicated by its narrow therapeutic index and wide intra- and interpatient variability. Tacrolimus population pharmacokinetics, including bioavailability, were investigated in an adult kidney transplant cohort to identify patient characteristics that influence pharmacokinetics.

Methods

The database (drug monitoring data) included 83 adult kidney transplant recipients and analysis was performed by a population approach with NONMEM. Data were collected during the first months after transplantation. Patients were administered oral or intravenous tacrolimus as part of a triple immunosuppressive regimen that also included mycophenolate mofetil and corticosteroids. Subsequent doses were adjusted on the basis of clinical evidence of efficacy and toxicity as in routine therapeutic drug monitoring.

Results

A one compartment open model with linear absorption and elimination adequately described the data. The typical value of minimal clearance was 1.8 ± 0.2 l h⁻¹. Clearance increased with time post transplantation to reach 50% of maximal value after 3.8 ± 0.5 days, with a maximal value of 5.6 l h⁻¹. Moreover clearance increased by approximately 1.6 fold (range 0.5–1.6) if the dose of prednisone was >25 mg. The typical value for volume of distribution, V, (98 ± 13 l kg⁻¹) was similar to reported values in kidney transplant patients. The oral bioavailability of tacrolimus was poor and ranged from 11.2 to 19.1%. No covariates significantly influenced V or F.

Conclusions

The number of days postoperation and corticosteroid dose were significant covariates influencing tacrolimus clearance.     

Biodegradable Nanoparticles Improve Oral Bioavailability of Amphotericin B and Show Reduced Nephrotoxicity Compared to Intravenous Fungizone®

Purpose

Amphotericin B (AMB), an effective antifungal and antileishmanial agent associated with low oral bioavailability (0.3%) and severe nephrotoxicity, was entrapped into poly(lactide-co-glycolide) (PLGA) nanoparticles to improve the oral bioavailability and to minimize the adverse effects associated with it.

Materials and Methods

The AMB-nanoparticles (AMB-NP) were prepared by nanoprecipitation method employing Vitamin E-TPGS as a stabilizer. In vitro release was carried out using membrane dialysis method. The in vitro hemolytic activity of AMB-NP was evaluated by incubation with red blood cells (RBCs). The acute nephrotoxicity profile and oral bioavailability of AMB-NP were evaluated in rats.

Results

The prepared AMB-NP formulation contained monodispersed particles in the size range of 165.6?±?2.9 nm with 34.5?±?2.1% entrapment at 10% w/w initial drug loading. AMB-NP formulation showed biphasic drug release, an initial rapid release followed by a sustained release. The AMB-NP formulation exerted lower hemolysis and nephrotoxicity as compared to Fungizone®. The relative oral bioavailability of the AMB-NP was found to be ～800% as compared to Fungizone®.

Conclusion

Together, these results offer a possibility of treating systemic fungal infection and leishmaniasis with oral AMB-NP, which could revolutionize the infectious disease treatment modalities.

     

Bioinspired Calcium Phosphate Nanoparticles Featuring as Efficient Carrier and Prompter for Macrophage Intervention in Experimental Leishmaniasis

Purpose

To develop a biocompatible and bioresorbable calcium phosphate (CaP) nanoparticles (NPs) bearing Amphotericin B (AmB) with an aim to provide macrophage specific targeting in visceral leishmaniasis (VL).

Materials & Methods

CaP-AmB-NPs were architectured through emulsion precipitation method. The developed formulation was extensively characterized for various parameters including in-vitro and in-vivo antileishmanial activity. Moreover, plasma pharmacokinetics, tissue biodistribution and toxicity profile were also assessed.

Results

Optimized CaP-AmB-NPs exhibited higher entrapment (71.1?±?6.68%) of AmB. No trend related to higher hemolysis was apparent in the developed formulation as evidenced in commercially available colloidal and liposomal formulations. Cellular uptake of the developed CaP-AmB-NPs was quantified through flow cytometry in J774A.1 cell line, and a 23.90 fold rise in uptake was observed. Fluorescent microscopy also confirmed the time dependent rise in uptake. In-vivo multiple dose toxicity study demonstrated no toxicity upto 5 mg/kg dose of AmB. Plasma kinetics and tissue distribution studies established significantly higher concentration of AmB in group treated with CaP-AmB-NPs in liver and spleen as compared to CAmB, LAmB and AmB suspension group. In-vivo animal experimental results revealed that the CaP-AmB-NPs showed higher splenic parasite inhibition compared to CAmB and LAmB in leishmania parasite infected hamsters.

Conclusions

The investigated CaP-AmB-NPs are effective in provoking macrophage mediated uptake and collectively features lower toxicity and offers a suitable replacement for available AmB-formulations for the obliteration of intra-macrophage VL parasite.

     

Pharmacokinetics,metabolism and bioavailability of the triazole antifungal agent voriconazole in relation to CYP2C19 genotype

AIMS

The aim was to determine the pharmacokinetics of voriconazole after a single oral dose in comparison with intravenous (i.v.) administration in healthy individuals stratified according to the cytochrome P450 (CYP) 2C19 genotype. In addition, the possible metabolic pathways and their modulation according to CYP2C19 genotype were investigated after oral and i.v. administration of voriconazole.

METHODS

In a single-centre, open-label, two-period crossover study 20 participants received single doses of 400 mg voriconazole orally and 400 mg voriconazole intravenously in randomized order. Blood and urine samples were collected up to 96 h post dose and the voriconazole and three major metabolites were quantified by high-performance liquid chromatography coupled to mass spectroscopy.

RESULTS

Absolute oral bioavailability of voriconazole was 82.6% (74.1, 91.0). It ranged from 94.4% (78.8, 109.9) in CYP2C19 poor metabolizers to 75.2% (62.9, 87.4) in extensive metabolizers. In contrast to voriconazole and its N-oxide, the plasma concentrations of both hydroxylated metabolites showed a large second peak after 24 h. Independent of the route of administration, voriconazole partial metabolic hydroxylation after i.v. administration was eightfold higher compared with N-oxidation [48.8 ml min⁻¹ (30.5, 67.1) vs. 6.1 ml min⁻¹ (4.1, 8.0)]. The formation of the metabolites was related to CYP2C19 activity.

CONCLUSIONS

Independent of the route of administration, voriconazole exposure was three times higher in CYP2C19 poor metabolizers compared with extensive metabolizers. Voriconazole has a high bioavailability with no large differences between the CYP2C19 genotypes. The hydroxylation pathway of voriconazole elimination exceeded the N-oxidation, both influenced by the CYP2C19 genotype.