Characterization of critical parameters using an air-liquid interface model with RPMI 2650 cells for permeability studies of small molecules

The field of nasal drug delivery gained enormously on interest over the past decade. Performing nasal in vivo studies is expensive and time-consuming, but also unfeasible for an initial high-throughput compound and formulation screening. Therefore, the development of fast and high-throughput in vitro models to screen compounds for their permeability through the nasal epithelium and mucosa is constantly expanding. Yet, the protocols used for nasal in vitro permeability studies are varying, which limits the comparability and reproducibility of generated data. This project aimed to elucidate the influence of different culture and assay parameters of RPMI 2650 cells grown under air-liquid interface (ALI) conditions on the transepithelial electrical resistance (TEER) and apparent permeability (Papp) values of five selected reference compounds, covering the range of low to moderate to high permeability. The influence of the passage number, seeding density, and timepoint of airlift was minimal in our approach, while the substrate pore density had a significant influence on the Papp values of carbamazepine, propranolol, and metoprolol, classified as highly permeable compounds, but not on atenolol and aciclovir. Elevation of the experimental concentration of carbamazepine, propranolol, and metoprolol in the donor compartment had an increasing effect on the Papp values, while prolonging the assay time did not have a significant influence. Based on the results reported here, RPMI 2650 cells cultured under ALI conditions offer the possibility of a standardized high-throughput screening model for small molecules and their formulations for in vitro drug permeation studies to predict and select optimal conditions for their nasal delivery.

Predictivity of Standardized and Controlled Permeation Studies: Ex vivo - In vitro - In vivo Correlation for Sublingual Absorption of Propranolol

In preclinical drug development, ex vivo and in vitro permeability studies are a decisive element for specifying subsequent development steps. In this context, reliability, physiological alignment and appropriate in vivo correlation are mandatory for predictivity regarding drug absorption. Especially in oromucosal drug delivery, these prerequisites are not adequately met, which hinders its progressive development and results in the continuous need for animal experiments. To address current limitations, an innovative, standardized, and controlled ex vivo permeation model was applied. It is based on Kerski diffusion cells embedded in automated sampling and coupled to mass spectrometric quantification under physiologically relevant conditions. This study aimed to evaluate the predictivity of the developed model using porcine mucosa (ex vivo) in relation to data of sublingual propranolol absorption (in vivo). In addition, the usefulness of biomimetic barriers (in vitro) as a replacement for porcine mucosa was investigated. Therefore, solubility and permeability studies considering microenvironmental conditions were conducted and achieved good predictivity (R²=0.997) for pH-dependent permeability. A multiple level C correlation (R²≥0.860) between obtained permeability and reported pharmacokinetic animal data (AUC, C_max) was revealed. Furthermore, a point-to-point correlation was demonstrated for several sublingual formulations. The successful IVIVC confirms the standardized ex vivo model as a viable alternative to animal testing for estimating the in vivo absorption behavior of oromucosal pharmaceuticals.

Solid-phase microextraction for assessment of plasma protein binding, a complement to rapid equilibrium dialysis

Aim: Determination of plasma protein binding (PPB) is considered vital for better understanding of pharmacokinetic and pharmacodynamic activities of drugs due to the role of free concentration in pharmacological response. Methodology & results: Solid-phase microextraction (SPME) was investigated for measurement of PPB from biological matrices and compared with a gold standard approach (rapid equilibrium dialysis [RED]). Discussion & conclusion: SPME-derived values of PPB correlated well with literature values, and those determined by RED. Respectively, average protein binding across three concentrations by RED and SPME was 33.1 and 31.7% for metoprolol, 89.0 and 86.6% for propranolol and 99.2 and 99.0% for diclofenac. This study generates some evidence for SPME as an alternative platform for the determination of PPB.

Development and Evaluation of a Physiologically Based Pharmacokinetic Drug-Disease Model of Propranolol for Suggesting Model Informed Dosing in Liver Cirrhosis Patients

AIM

The study was aimed to understand the underlying causes for the differences in propranolol pharmacokinetics (PK) between healthy and cirrhosis populations by using a systematic whole-body physiologically based pharmacokinetic (PBPK) model-building approach for suggesting model informed propranolol dosing in liver cirrhosis patients with different stages of disease severity.

METHODS

A whole-body PBPK model was developed by using population simulator PK-Sim® by using reported physicochemical and clinical data for propranolol in healthy and liver cirrhosis populations. The model evaluation was done by visual verification and comparison of PK parameters using their observed/predicted ratios (Robs/pred).

RESULTS

The developed model has effectively described the disposition of propranolol after intravenous and oral application in healthy and liver cirrhosis populations. All the model predictions were comparable to the observed clinical data and the Robs/pred for all the PK parameters were within a 2-fold range. A significant increase in plasma concentration of propranolol and decrease in drug clearance was observed in progressive stages of liver cirrhosis. The developed model after evaluation with the reported clinical PK data was used for suggesting model informed propranolol dosing in different stages of liver cirrhosis based on systemic unbound drug concentration.

CONCLUSION

The developed PBPK model has successfully described propranolol PK in healthy and cirrhosis populations after IV and oral administration. The evaluated PBPK propranolol-cirrhosis model can have many implications in predicting propranolol dosing in liver cirrhosis patients with different stages of disease severity.

Absolute quantitation of propranolol from 200-μm regions of mouse brain and liver thin tissues using laser ablation-dropletProbe-mass spectrometry

RATIONALE

The ability to quantify drugs and metabolites in tissue with sub-mm resolution is a challenging but much needed capability in pharmaceutical research. To fill this void, a novel surface sampling approach combining laser ablation with the commercial dropletProbe automated liquid surface sampling system (LA-dropletProbe) was developed and is presented here.

METHODS

Parylene C-coated 200 × 200 μm tissue regions of mouse brain and kidney thin tissue sections were analyzed for propranolol by laser ablation of tissue directly into a preformed liquid junction. Propranolol was detected by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) in positive electrospray ionization mode. Quantitation was achieved via application of a stable-isotope-labeled internal standard and an external calibration curve.

RESULTS

The absolute concentrations of propranolol determined from 200 × 200 μm tissue regions were compared with the propranolol concentrations obtained from 2.3-mm-diameter tissue punches of adjacent, non-coated sections using standard bulk tissue extraction protocols followed by regular HPLC/MS/MS analysis. The average concentration of propranolol in both organs determined by the two employed methods agreed to within ±12%. Furthermore, the relative abundances of phase II hydroxypropranolol glucuronide metabolites were recorded and found to be consistent with previous results.

CONCLUSIONS

This work illustrates that depositing a thin layer of parylene C onto thin tissue prior to analysis, which seals the surface and prevents direct liquid extraction of the drug from the tissue, coupled to the novel LA-dropletProbe surface sampling system is a viable approach for sub-mm resolution quantitative drug distribution analysis.

Integrated laser ablation-dropletProbe-mass spectrometry for absolute drug quantitation, metabolite detection, and distribution in tissue

RATIONALE

Spatially resolved and accurate quantitation of drug-related compounds in tissue is a much-needed capability in drug discovery research. Here, application of an integrated laser ablation-dropletProbe-mass spectrometry surface sampling system (LADP-MS) is reported, which achieved absolute quantitation of propranolol measured from <500 × 500 μm thin tissue samples.

METHODS

Mouse liver and kidney thin tissue sections were coated with parylene C and analyzed for propranolol by a laser ablation/liquid extraction workflow. Non-coated adjacent sections were microdissected for validation and processed using standard bulk tissue extraction protocols. High-performance liquid chromatography with positive ion mode electrospray ionization tandem mass spectrometry was applied to detect the drug and its metabolites.

RESULTS

Absolute propranolol concentration in ~500 × 500 μm tissue regions measured by the two methods agreed within ±8% and had a relative standard deviation within ±17%. Quantitation down to ~400 × 400 μm tissue regions was shown, and this resolution was also used for automated mapping of propranolol and phase II hydroxypropranolol glucuronide metabolites in kidney tissue.

CONCLUSIONS

This study exemplifies the capabilities of integrated laser ablation-dropletProbe-mass spectrometry (LADP-MS) for high resolution absolute drug quantitation analysis of thin tissue sections. This capability will be valuable for applications needing to quantitatively understand the spatial distribution of small molecules in tissue.

Pharmacokinetic variability of beta-adrenergic blocking agents used in cardiology

The aim of this study was to evaluate the pharmacokinetic variability of beta-adrenergic blocking agents used in cardiology by reviewing single-dose and steady-state pharmacokinetic studies from the literature. PubMed was searched for pharmacokinetic studies of beta-adrenergic blocking agents, both single-dose and steady-state studies. The studies included reported maximum plasma concentration (Cmax) and/or area under the concentration curve (AUC). The coefficient of variation (CV%) was calculated for all studies, and a CV% <40% was considered low or moderate variability, and a CV% >40% was considered high variability. The Cmax and AUC were reported a total of 672 times in 192 papers. Based on AUC, metoprolol, propranolol, carvedilol, and nebivolol showed high pharmacokinetic variability (highest first), whereas bisoprolol, atenolol, sotalol, labetalol, nadolol, and pindolol showed low to moderate variability (lowest first). We have shown a high interindividual pharmacokinetic variability that varies markedly in different beta-adrenergic blocking agents; the extreme being steady state ratios as high as 30 in metoprolol. A more personalized approach to the medical treatment of patients may be obtained by combining known pharmacokinetic information about variability, pharmaco-genetics and -dynamics, and patient characteristics, to avoid adverse events or lack of treatment effect.

Development and characterization of a nanoemulsion containing propranolol for topical delivery

BACKGROUND

Propranolol (PPN) is a therapeutic option for the treatment of infantile hemangiomas. This study aimed at the development of nanoemulsion (NE) containing 1% PPN, characterization of the system, and safety studies based on ex vivo permeation, cytotoxicity, and biodistribution in vivo.

METHODS

The formulation was developed and characterized in relation to the droplet size, polydispersity index (PDI), pH, zeta potential, and electronic microscopy. Ex vivo permeation studies were used to evaluate the cutaneous retention of PPN in the epidermis and dermis. Cytotoxicity studies were performed in fibroblasts, macrophages, and keratinocytes. In vivo biodistribution assay of the formulations was performed by means of labeling with technetium-99m.

RESULTS

NE1 exhibited droplet size of 26 nm, PDI <0.4, pH compatible with the skin, and zeta potential of -20 mV, which possibly contributes to the stability. Electron microscopy showed that the NE presented droplets of nanometric size and spherical shape. NE1 provided excellent stability for PPN. In the ex vivo cutaneous permeation assay, the NE provided satisfactory PPN retention particularly in the dermis, which is the site of drug action. In addition, NE1 promoted cutaneous permeation of the PPN in small amount. In vivo biodistribution showed that the radiolabeled formulation remained in the skin and a small amount reached the bloodstream. NE1 presented low cytotoxicity to fibroblasts, macrophages, and keratinocytes in the concentrations evaluated in the cytotoxicity assay.

CONCLUSION

We concluded that the formulation is safe for skin administration; however, cutaneous irritation studies should be performed to confirm the safety of the formulation before clinical studies in patients with infantile hemangiomas.

A mass spectrometry imaging approach for investigating how drug-drug interactions influence drug blood-brain barrier permeability

There is a high need to develop quantitative imaging methods capable of providing detailed brain localization information of several molecular species simultaneously. In addition, extensive information on the effect of the blood-brain barrier on the penetration, distribution and efficacy of neuroactive compounds is required. Thus, we have developed a mass spectrometry imaging method to visualize and quantify the brain distribution of drugs with varying blood-brain barrier permeability. With this approach, we were able to determine blood-brain barrier transport of different drugs and define the drug distribution in very small brain structures (e.g., choroid plexus) due to the high spatial resolution provided. Simultaneously, we investigated the effect of drug-drug interactions by inhibiting the membrane transporter multidrug resistance 1 protein. We propose that the described approach can serve as a valuable analytical tool during the development of neuroactive drugs, as it can provide physiologically relevant information often neglected by traditional imaging technologies.

Uptake, depuration, and bioconcentration of two pharmaceuticals, roxithromycin and propranolol, in Daphnia magna

The objective of the present study was to investigate the uptake, depuration, and bioconcentration of two pharmaceuticals, roxithromycin (ROX) and propranolol (PRP), in Daphnia magna via aqueous exposure. Additionally, dietary and pH effects on the bioconcentration of two pharmaceuticals in daphnia were studied. During the 24-h uptake phase followed by the 24-h depuration phase, the uptake rate constants (k(u)) of ROX for daphnia were 9.21 and 2.77 L kg(-1) h(-1), corresponding to the exposure concentrations of 5 and 100 μg L(-1), respectively; For PRP at the nominal concentrations of 5 and 100 μg L(-1), k(u) were 2.29 and 0.99 L kg(-1) h(-1), respectively. The depuration rate constants (k(d)) of ROX in daphnia, at the exposure concentrations of 5 and 100 μg L(-1), were 0.0985 and 0.207 h(-1), respectively; while those of PRP were 0.0276 and 0.0539 h(-1) for the nominal concentrations of 5 and 100 μg L(-1), respectively. With the decreasing exposure concentrations, the bioconcentration factors (BCFs) in daphnia ranged from 13.4 to 93.5 L kg(-1) for ROX, and 18.4 to 83.0 L kg(-1) for PRP, revealing the considerable accumulation potential of these two pharmaceuticals. Moreover, after 6h exposure, the body burdens of ROX and PRP in dead daphnia were 4.98-6.14 and 7.42-12.9 times higher than those in living daphnia, respectively, implying that body surface sorption dominates the bioconcentration of the two pharmaceuticals in daphnia. In addition, the presence of algal food in the media could significantly elevate the kd values for both ROX and PRP, thereby restraining their bioconcentration in daphnia. A pH-dependent bioconcentration study revealed that the bioconcentration of the two pharmaceuticals in daphnia increased with increasing pH levels, which ranged from 7 to 9. Finally, a model was developed to estimate the relationships between pH and the BCFs of the two pharmaceuticals in zooplankton. The predicted values based on this model were highly consistent with wildlife monitoring data, implying that this model will be useful in identifying the bioaccumulation risks that pharmaceuticals pose to zooplankton.

[Effect of acute exposure to high altitude on pharmacokinetics of propranolol and metoprolol in rats]

OBJECTIVE

To study the pharmacokinetics of propranolol and metoprolol in rats after acute exposure to high altitude.

METHODS

Wistar rats were randomly assigned into 4 groups for treatment with intragastric administration of propranolol or metoprolol after acute exposure to high altitude (4010 m) or normal altitude (50 m). Venous blood samples were collected from the rats at different time points after drug administration to determine the drug concentrations in the plasma and plasma ultrafiltrate using liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS

The protein binding rate of propranolol was significantly increased but that of metoprolol remained unchanged after acute exposure to high altitude. Compared with the rats exposed to normal altitude, the rats with acute exposure to high altitude showed significant alterations in the pharmacokinetic parameters of the drugs, shown by increased Cmax and AUC, prolonged t1/2 and MRT, and lowered Clz/F of propranolol, and by increased Tmax and prolonged t1/2 and MRT of metoprolol without obvious changes of the parameters of the compartmental model.

CONCLUSION

Significant changes in the pharmacokinetics of propranolol and metoprolol occur in rats after acute exposure to high altitude possibly in relation to, apart from the changes in plasma protein binding ratio and blood gas, alterations in metabolic enzyme activities, increased blood viscosity, and species and general conditions of the animals.

[Effect of liver cirrhosis on pharmacokinetics and pharmacodynamics of drugs]

Metabolic liver functions are significantly involved in the total clearance of a number of drugs. In liver cirrhosis the reduced drug elimination is a result of the blood flow through the liver, hepatocytes function and volume of hepatic tissue. Pharmacokinetic and pharmacodynamic changes depend on the nature and degree of hepatic impairment and on the characteristics of the dosed drug. Hepatocytes have a different extraction ability with respect to the individual drugs. The following are examples of drugs with high hepatic extraction: anodyne, propranolol, metoprolol, verapamil and lidocaine. These drugs are significantly dependent on the first passage through the liver. Intrahepatic and extrahepatic collateral blood flows significantly increase their bio-logical availability and reduce the clearance. The reduction in hepatic clearance of drugs with low extraction coefficient, such as chlordiazepoxide, diazepam or furosemide, is a result of its own limited functional capacity to eliminate the drug. Predicting a hepatic metabolic disorder based on a common bio-chemical assessment of enzyme activities is not sufficient. In advanced liver cirrhosis a higher risk is demonstrated for drugs with a narrow therapeutic width. It is always necessary to take into account whether the pharmacotherapy is necessary, use small doses and cautiously monitor the patient.

Photoconjugation of molecularly imprinted polymer with magnetic nanoparticles

Because of their synthetic accessibility, molecularly imprinted polymer (MIP) nanoparticles are ideal building blocks for preparing multifunctional composites. In this work, we developed a general photocoupling chemistry to enable simple conjugation of MIP nanoparticles with inorganic magnetic nanoparticles. We first synthesized MIP nanoparticles using propranolol as a model template and perfluorophenyl azide-modified silica-coated magnetic nanoparticles. Using a simple photoactivation followed by facile purification with a magnet, we obtained magnetic composite particles that showed selective uptake of propranolol. We characterized the nanoparticles and composite materials using FT-IR, TEM, fluorescence spectroscopy, and radioligand binding analysis. Through the high molecular selectivity of the magnetic composite, we demonstrated the nondestructive feature and the high efficiency of the photocoupling chemistry. The versatile photoconjugation method developed in this work should also be very useful for combining organic MIPs with other inorganic nanoparticles to enable new chemical sensors and high efficiency photocatalysts.

Design and in vitro evaluation of effervescent gastric floating drug delivery systems of propanolol HCl

Abstract. The purpose of this research was to develop and evaluate effervescent gastric floating tablets of propranolol HCl. The oral delivery of antihypertensive propranolol HCl was facilitated by preparing an effervescent floating dosage form which could increase its absorption in the stomach by increasing the drug's gastric residence time. In the present work, effervescent floating tablets were prepared with a hydrophilic carrier such as polyethylene oxide (PEO WSR N 60K and PEO WSR 303) as a release retarding agent and sodium bicarbonate as a gas generating agent. The prepared tablets were evaluated for all their physicochemical properties, in vitro buoyancy, drug release and rate order kinetics. From the results, P9 was selected as an optimized formulation based on their 12 h drug release, minimal floating lag time and maximum total floating time. The optimized formulation followed first order rate kinetics with erosion mechanism. The optimized formulation was characterized with FTIR studies and no interaction between the drug and the polymers were observed.

Rapid analysis of isomeric exogenous metabolites by differential mobility spectrometry-mass spectrometry

The direct separation of isomeric glucuronide metabolites from propranolol dosed tissue extracts by differential mobility spectrometry-mass spectrometry (DMS-MS) with the use of the polar gas-phase chemical modifier acetonitrile was demonstrated. The DMS gas-phase separation was able to resolve the isomeric metabolites with separation times on the order of milliseconds instead of minutes which is typically required when using pre-ionization chromatographic separation methods. Direct separation of isomeric metabolites from the complex tissue extract was confirmed by implementing a high-performance liquid chromatography (HPLC) separation prior to the DMS-MS analysis to pre-separate the species of interest. The ability to separate isomeric exogenous metabolites directly from a complex tissue extract is expected to facilitate the drug development process by increasing analytical throughput without the requirement for pre-ionization cleanup or separation strategies.

Guar gum, xanthan gum, and HPMC can define release mechanisms and sustain release of propranolol hydrochloride

The objectives were to characterize propranolol hydrochloride-loaded matrix tablets using guar gum, xanthan gum, and hydroxypropylmethylcellulose (HPMC) as rate-retarding polymers. Tablets were prepared by wet granulation using these polymers alone and in combination, and physical properties of the granules and tablets were studied. Drug release was evaluated in simulated gastric and intestinal media. Rugged tablets with appropriate physical properties were obtained. Empirical and semi-empirical models were fit to release data to elucidate release mechanisms. Guar gum alone was unable to control drug release until a 1:3 drug/gum ratio, where the release pattern matched a Higuchi profile. Matrix tablets incorporating HPMC provided near zero-order release over 12 h and erosion was a contributing mechanism. Combinations of HPMC with guar or xanthan gum resulted in a Higuchi release profile, revealing the dominance of the high viscosity gel formed by HPMC. As the single rate-retarding polymer, xanthan gum retarded release over 24 h and the Higuchi model best fit the data. When mixed with guar gum, at 10% or 20% xanthan levels, xanthan gum was unable to control release. However, tablets containing 30% guar gum and 30% xanthan gum behaved as if xanthan gum was the sole rate-retarding gum and drug was released by Fickian diffusion. Release profiles from certain tablets match 12-h literature profiles and the 24-h profile of Inderal(®) LA. The results confirm that guar gum, xanthan gum, and HPMC can be used for the successful preparation of sustained release oral propranolol hydrochoride tablets.

The intestinal permeability of neolignans from the seeds of Myristica fragrans in the Caco-2 cell monolayer model

The intestinal permeability and transport of 10 neolignans isolated from MYRISTICA FRAGRANS were studied by using the Caco-2 cell monolayer model. The 10 neolignans were measured by HPLC. Transport parameters and permeability coefficients were then calculated and compared with those of the model compounds, propranolol and atenolol. Among the 10 neolignans, the 8- O-4'-type neolignans demonstrated high permeability while the benzofuran-type neolignans were of poor to moderate permeability. Among them, eight neolignans were transported mainly VIA passive diffusion. These findings indicate that the 8- O-4'-type neolignans are well-absorbed compounds and can be used as oral leading compounds in drug discovery.

[Beta blockers in migraine prophylaxis]

Beta blockers (beta-adrenoceptor blockers) are known to be used for the prophylactic treatment of migraine. The improvement of migraine in the patients who recieved propranolol for angina pectoris revealed the effectiveness of propranolol in migraine prophylaxis. Many clinical trials have confirmed that propranolol is effective in the prophylactic treatment of migraine. Other beta-blocking drugs, namely nadolol, metoprolol, atenolol, timolol and bisoprolol, have also been demonstrated to be effective in the prophylaxis of migraine. In contrast, several beta blockers with intrinsic sympathetic activity (ISA), such as alprenolol, oxprenolol, pindolol and acebutolol, have not been demonstrated to be effective in migraine prophylaxis. In this review, we have descrived the pharmacologic background and pharmacokinetics of the beta blockers that demonstrated a prophylactic effect for migraine will be described. We have also reviewed the results of clinical trials of beta-blocking drugs for migraine.

Formulation and evaluation of gastroretentive drug delivery system of propranolol hydrochloride

The objective of present study was to develop a gastroretentive drug delivery system of propranolol hydrochloride. The biggest problem in oral drug delivery is low and erratic drug bioavailability. The ability of various polymers to retain the drug when used in different concentrations was investigated. Hydroxypropyl methylcellulose (HPMC) K4 M, HPMC E 15 LV, hydroxypropyl cellulose (HPC; Klucel HF), xanthan gum, and sodium alginate (Keltose) were evaluated for their gel-forming abilities. One of the disadvantages in using propranolol is extensive first pass metabolism of drug and only 25% reaches systemic circulation. The bioavailability of propranolol increases in presence of food. Also, the absorption of various drugs such as propranolol through P-glycoprotein (P-gp) efflux transporter is low and erratic. The density of P-gp increases toward the distal part of the gastrointestinal tract (GIT). Therefore, it was decided to formulate floating tablet of propranolol so that it remains in the upper part of GIT for longer time. They were evaluated for physical properties, in vitro release as well as in vivo behavior. In preliminary trials, tablets formulated with HPC, sodium alginate, and HPMC E 15 LV failed to produce matrix of required strength, whereas formulation containing xanthan gum showed good drug retaining abilities but floating abilities were found to be poor. Finally, floating tablets were formulated with HPMC K4 M and HPC.

Uptake of propranolol, a cardiovascular pharmaceutical, from water into fish plasma and its effects on growth and organ biometry

Pharmaceuticals in the environment (PIE) are of importance since these compounds are designed to affect biological receptors/enzymes that are often conserved across vertebrate families. Across-species extrapolation of these therapeutic targets suggests potential for impacting amphibia and fish in the aquatic environment. Due to the scarcity of relevant ecotoxicological data, the long-tem impact of PIE remains a research question. Efficient use of mammalian data has been proposed to better understand and predict the potential for a given pharmaceutical to impact the environment. Using a model cardiovascular pharmaceutical (propranolol, a non-specific beta(1)/beta(2)-adrenergic antagonist), the hypothesis that mammalian data can be used to predict toxicity in fish was tested. Rainbow trout (Oncorhynchus mykiss (Walbaum)) have beta-adrenergic signalling mechanisms analogous to human cardiovascular receptors that respond to pharmacological doses of agonists and antagonists. Trout absorbed propranolol from water such that after 40 days of exposure, the linear relationship was [plasma] - 0.59[water] (n - 31, r - 0.96). Growth rate was affected only at very high aqueous concentrations (10-day (growth)NOEC - 1.0 and (growth)LOEC - 10 mg/l). Growth recovered with time (40-day (growth)NOEC - 10 mg/l), suggesting possible adaptation to the pharmaceutical, although the internal plasma concentration in trout exposed to 10mg propranolol/l of water was higher than the mammalian therapeutic plasma concentration. Additional endpoints suggested subtle changes of liver and heart size at much lower concentrations may have occurred, although these were not concentration-related. There was, however, a dose-dependent effect upon overall body condition. The trout plasma concentrations at these effective aqueous concentrations fell within the range of mammalian effective plasma concentrations, supporting the potential for developing 'read-across' from mammalian pharmacology safety data to fish ecotoxicology. Despite these effects at relatively high concentrations, propranolol is not expected to pose a risk to fish at the concentrations considered to be present in the aquatic environment.

Evaluation of the metabolism of propranolol by linear ion trap technology in mouse, rat, dog, monkey, and human cryopreserved hepatocytes

Propranolol is a widely used quality control and validation compound for liver microsome and hepatocyte metabolism studies. A multitude of literature reports describing the identification of propranolol metabolites exists today. However, no literature reports currently exist showing hepatocyte metabolism across the five species commonly used during pre-clinical drug discovery, namely mouse, rat, dog, monkey, and human. Herein, we present full metabolic profiles of propranolol in mouse, rat, dog, monkey and human hepatocytes. As expected, extensive phase I and phase II metabolism was observed across all five species and species-specific metabolites were detected in monkey and dog hepatocytes. Of particular interest was the detection of an N-hydroxylamine glucuronide metabolite in monkey and dog hepatocytes.

Segmental-dependent membrane permeability along the intestine following oral drug administration: Evaluation of a triple single-pass intestinal perfusion (TSPIP) approach in the rat

In this paper we evaluate a modified approach to the traditional single-pass intestinal perfusion (SPIP) rat model in investigating segmental-dependent permeability along the intestine following oral drug administration. Whereas in the traditional model one single segment of the intestine is perfused, we have simultaneously perfused three individual segments of each rat intestine: proximal jejunum, mid-small intestine and distal ileum, enabling to obtain tripled data from each rat compared to the traditional model. Three drugs, with different permeabilities, were utilized to evaluate the model: metoprolol, propranolol and cimetidine. Data was evaluated in comparison to the traditional method. Metoprolol and propranolol showed similar P(eff) values in the modified model in all segments. Segmental-dependent permeability was obtained for cimetidine, with lower P(eff) in the distal parts. Similar P(eff) values for all drugs were obtained in the traditional method, illustrating that the modified model is as accurate as the traditional, throughout a wide range of permeability characteristics, whether the permeability is constant or segment-dependent along the intestine. Three-fold higher statistical power to detect segmental-dependency was obtained in the modified approach, as each subject serves as his own control. In conclusion, the Triple SPIP model can reduce the number of animals utilized in segmental-dependent permeability research without compromising the quality of the data obtained.

Radical Crosslinked Albumin Microspheres as Potential Drug Delivery Systems: Preparation and In Vitro Studies

This article reports on the preparation of acryloylated bovine serum albumin microspheres and the evaluation of their employment in drug delivery areas. The influence of preparation parameters on albumin microspheres and the chemicophysical properties of loaded drugs were investigated. In particular, we focussed on acylation albumin degree and the amount of acryloylated albumin against comonomer in the polymerization step. Finally the release profile took into consideration the interaction drug-matrix, the fuctionalization degree of albumin, and the water affinity of matrix.

Increase in the vascular residence time of propranolol-loaded nanoparticles coated with heparin

Propranolol-HCI incorporated nanoparticles prepared with a blend of a polyester and a polycationic polymer and coated or not with a low molecular weight heparin by electrostatic interactions were prepared by emulsification followed by solvent evaporation. The mean diameter was 388 and 357 nm for coated and uncoated nanoparticles, respectively, and the entrapment efficiency ranged from 20 to 32%. Coated nanoparticles were negatively-charged, whereas uncoated nanoparticles displayed a positive zeta potential (+30 mV). After intravenous administration to rabbits of propranolol-HCI solution and propranolol-loaded nanoparticles coated or not with heparin, pharmacokinetic data revealed that coated nanoparticles exhibited a prolonged blood residence time. It can be concluded that the hydrophilic layer of heparin at the surface of nanoparticles conferred stealth properties which probably reduce the phagocytosis process and avoid immediate uptake by the mononuclear phagocytic system.

In vitro and in vivo evaluation of locust bean gum and chitosan combination as a carrier for buccal drug delivery

The object of the study was to evaluate locust bean gum and chitosan in ratios of 2:3; 3:2 and 4:1 (F1, F2 and F3) as a mucoadhesive component in buccal tablets and to compare the bioavailability of a propranolol hydrochloride buccal tablet with the oral tablet in healthy human volunteers. Propranolol hydrochloride buccal tablets containing various weight ratios of locust bean gum and chitosan were prepared and coated with 5% w/v ethyl cellulose on one face, and oral tablets containing 10 mg propranolol hydrochloride alone were formulated using a direct compression technique. The strength of mucoadhesion of the tablets was quantified based on the tensile force required to break the adhesive bond between a model membrane (porcine buccal mucosa) and the test polymer. The forces of detachment for the mucoadhesive buccal tablets were 14.61 +/- 0.14, 13.21 +/- 0.13 and 11.71 +/- 0.12. An in vitro study was carried out in pH 6.8 phosphate buffer and the cumulative percentage release of propranolol measured at 10 min intervals for 600 min was found to be 98.31 +/- 0.10, 92.24 +/- 0.41 and 90.18 +/- 0.76 respectively. A bioavailability study was conducted with the prepared formulation in 16 healthy human volunteers to determine the plasma concentration of propranolol at 0, 1, 2, 3, 4, 6, 8, 10 and 12 h. The bioavailability (AUC(0-t*) ng x h/ml) of the buccal propranolol hydrochloride tablets (F1, F2 and F3) and oral tablet (F4) was found to be 2244.18 +/- 210, 3580.69 +/- 460, 3889.19 +/- 290 and 1732 +/- 96 ng x hr/ml respectively. The study indicates that locust bean gum and chitosan in a weight ratio of 2:3 (F1) not only releases the drug unidirectionally from the dosage form, but also gives buccal tablets which are sufficiently mucoadhesive for clinical applications.

Evaluation of in vitro biotransformation of propranolol with HPLC, MS/MS, and two bioassays

The majority of human drugs enter aquatic systems after ingestion and subsequent excretion in the form of parent compounds and metabolites. Environmental exposure to drug metabolites has not been reported so far. The goal of the present study was to apply the in vitro method of biotransformation of compounds with S9 fraction to the ecotoxicological analysis. beta-adrenoceptor antagonist propranolol was metabolized with S9 rat liver fraction. The parent compound was quantified with HPLC, and the metabolites were identified with QToF MS. Propranolol was metabolized rapidly, during the first hour its level decreased by 80 and 50% of the initial 20 and 100 mg L(-1), respectively. Ten peaks were observed on the HPLC-RF chromatogram. Four peaks were identified with QToF MS/MS propranolol (m/z = 260), N-desisopropylpropranolol (m/z = 218), hydroxypropranolol (m/z = 276), and hydroxy N-desisopropranolol glycol (m/z = 235). Then the ecotoxicity of the reaction mixture was studied with two bioassays Spirotox with the protozoan Spirostomum ambiguum and Thamnotoxkit F with the anostracean crustacean Thamnocephalus platyurus. Propranolol is twofolds more toxic to Spirotox than to Thamnotoxkit F with 24 h-EC50 = 1.77 mg L(-1) and 24 h-LC50 = 3.86 mg L(-1), respectively. No statistically significant differences were found between the toxicity of the reaction mixtures after S9 biotransformation and the propranolol solution. These results indicate that the biological activity of the metabolites is similar to that of the parent drug. The presented method of in vitro biotransformation of drugs with S9 fraction followed by HPLC and ecotoxicity tests, may be used as screening method for evaluation of the toxicity of drug metabolites.

Analysis of hepatic metabolism affecting pharmacokinetics of propranolol in humans

We examined the metabolic kinetics of propranolol, constructed from saturable and non-saturable components, using liver microsomes. The metabolic activity in rat microsomes was much higher than that in human microsomes within the clinically observed plasma range. Using the physiologically based pharmacokinetic (PBPK) model incorporating the obtained metabolic parameters, the plasma kinetics of propranolol was well correlated with reported values, and then used to analyze the effect of hepatic first-pass metabolism on propranolol plasma pharmacokinetics in clinical doses. The simulated plasma concentrations and AUC values of propranolol increased proportionally to its dose; these levels were almost equivalent to intrinsic clearance (CLint1), presumed to be non-saturable. When Michaelis-Menten parameters were decreased to one twentieth, plasma concentrations slightly increased after 160 mg dosing. A similar result was obtained with steady-state plasma levels after repeated administration. On the other hand, the first-order absorption rate constant of propranolol did not affect AUC values. The dose-normalized AUC value started to increase about 10(3)mg dosing. When the dose exceed 10(6)mg dose, the CLint1 component hardly contributed to propranolol pharmacokinetics. Accordingly, under the conditions of the PBPK model, propranolol pharmacokinetics was considered to be dose-independent within the clinical dose range.

Reproducible and time-dependent modification of serum protein binding in Wistar Kyoto rats

INTRODUCTION

The theoretical basis of the influence of (alterations in) plasma protein binding on pharmacokinetics (PK) is well-established. In contrast, the impact of protein binding on pharmacodynamics has not been examined in a systematic manner. Here we present an experimental approach to modify serum protein levels and binding in the rat, in a robust, reproducible, and time-dependent manner.

METHOD

Male Wistar Kyoto rats were divided into three different groups. The control group (n=4) did not receive treatment. In the cannulation(-) group (n=6) the rats were instrumented with three permanent blood cannulas. The rats in the cannulation(+) group received in addition to the cannulation a subcutaneous injection of turpentine oil of 100 microl/100 g bodyweight. The effects were characterized in terms of 1) the time course of serum levels of albumin and alpha(1)-acid glycoprotein (AGP), and 2) the effect on the ex vivo serum protein binding of S(-)-propranolol.

RESULTS

In control rats the AGP serum concentration was stable at a value of 169+/-16 microg/ml. In the cannulation(-) group a maximum ten- to fifteen-fold increase in serum AGP concentration was observed at 48 h post surgery, followed by a gradual return back to baseline within 1 week. In the cannulation(+) group a similar concentration-time profile for AGP was found, but without a complete return to baseline within 1 week and with a much higher variability. Ex vivo, an increase in AGP serum concentration from 55 to 675 microg/ml resulted in a profound decrease in the free fraction of S(-)-propranolol from 14+/-0.6 to 1.9+/-0.3%.

CONCLUSIONS

In conclusion, through cannulation alone the serum protein levels and binding were modified in a robust, reproducible and time-dependent manner. Therefore this experimental approach is suitable for the investigation of the influence of protein binding on both pharmacokinetics and pharmacodynamics.

Propranolol plasma monitoring in children submitted to surgery of tetralogy of Fallot by a micromethod using high performance liquid chromatography

OBJECTIVE

To evaluate the analytical micromethod using liquid chromatography for the quantification of propranolol in children submitted to surgery of tetralogy of Fallot (TLF).

METHODS

Only 0.2 mL of plasma is required for the assay. Peaks eluted at 8.4 (Propranolol) and 17.5 min (verapamil, internal standard) from a C18 column, with a mobile phase 0.1 M acetate buffer, pH 5.0, and acetonitrile (60:40, v/v) at flow rate 0.7 mL/min, detected at 290 nm (excitation) and 358 nm (emission). Surgery was started 776 min of drug administration (8.7 mg, mean); seven blood samples were collected from six patients (4M/2F; 2.1 yrs;11.5 kg; 0.80 m; 18.9 kg/m(2)).

RESULTS

Confidence limits of the method showed high selectivity and recovery, sensitivity of 0.02ng/mL, good linearity (0.05-1000 ng/mL), precision of 8.6% and accuracy of 3.1%. The mean duration of surgery was 283.2 min, with the patients remaining under cardiopulmonary bypass (CPB) for 114 min. A declining curve of propranolol plasma concentration was obtained after the last dose in the night that preceded the day of surgery. Plasma concentration also was normalized with hematocrit due to the hemodilution caused by the CPB procedure. On the other hand a decrease on drug plasma concentration was obtained between periods, the beginning of surgery to the postoperative day 2 (7.09 ng/mL and 0.05 ng/mL, p<0.05 respectively) and from the end of CPB to the postoperative day 2 (2.79 ng/mL e 0.05 ng/mL, p<0.05).

CONCLUSION

Propranolol monitoring of plasma concentrations of children (TLF) normalized after the last preoperative dose revealed a decline from the beginning of surgery to the second postoperative day, suggesting that, once redistribution was restored, propranolol washout was complete.

Comparison of a Chronotherapeutically Administered β Blocker vs. a Traditionally Administered β Blocker in Patients With Hypertension

Increasing systolic blood pressure and heart rate during the early morning results in increased myocardial oxygen demand. The use of beta blockers during this period may decrease cardiac workload, particularly in beta-blocker sensitive patients. The impact of a new chronotherapeutic beta blocker was assessed in 44 hypertensive patients. Patients were randomized to delayed-release propranolol (INP) dosed at 10 p.m. or to traditionally dosed propranolol (ILA) dosed at 8 a.m. for 4 weeks, following which they were switched to the alternative formulation for 4 weeks. Thirty-four-hour ambulatory blood pressure monitoring and pharmacokinetic measurements were obtained. INP and ILA resulted in significant reductions in mean 24-hour blood pressure (-9.0/-6.9 mm Hg and -10.4/-7.7 mm Hg, respectively). The top 25% of responders to high-dose propranolol (sensitive patients) were compared on each formulation. Mean trough reductions were -8.0/-6.7 mm Hg and -7.6/-5.8 mm Hg, respectively. Mean blood pressure reductions in the beta-blocker sensitive patients (n = 11) between 6 a.m. and noon were -15.2/-11.9 mm Hg on INP and -8.0/-4.6 mm Hg on ILA. Heart rate reduction was -14.1 bpm and double product reduction was -3319 in the INP patients between 6 a.m. and 12 noon compared with -10.5 and -2209 in the ILA patients. This study suggests that INP and ILA are effective once-a-day beta blockers, but the use of delayed-release propanolol results in a greater reduction in double product between 6 a.m. and noon in beta-blocker sensitive patients than does traditionally dosed propranolol.

Saturable uptake of lipophilic amine drugs into isolated hepatocytes: mechanisms and consequences for quantitative clearance prediction

The hepatic uptake of quinine, fluvoxamine, and fluoxetine (0.1-10 microM) was investigated with freshly isolated rat hepatocytes. The cell-to-medium concentration ratios (K(p)) were concentration-dependent: the mean maximum K(p) values (at 0.1 microM) were 150 (quinine), 500 (fluvoxamine), and 2000 (fluoxetine). There was also a large capacity site that was not saturable over the concentration range used (possibly partition into the phospholipid component of membranes); representing this site, the mean minimum K(p) values (at 10 microM) were 30 (quinine), 200 (fluvoxamine), and 500 (fluoxetine). To eliminate concomitant metabolism, cells were pretreated with the irreversible P450 inhibitor, aminobenzotriazole. The saturable uptake was substantially eliminated after exposure to carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (ATP inhibitor). The difference between the maximum and minimum K(p) for these three amine drugs, as well as for dextromethorphan, propranolol, and imipramine, was within a limited range of 3-fold, indicating a common magnitude of saturable uptake. Basic, permeable drugs are expected to be sequestered into lysosomes, which actively maintain their low internal pH (approximately 5) using ATP, and this process is predictable from the combined effects of pH-driven ion accumulation and unsaturable binding representing partition into membranes. The resultant predicted maximum K(p) correlated strongly with the observed maximum K(p). Thus, at low substrate concentrations, the fraction of drug unbound in the hepatocyte incubation (critical for assessing drug clearance and drug-drug interaction potential) may be dependent upon saturable as well as unsaturable binding, and for lipophilic, basic drugs, this can be readily estimated assuming a common degree of uptake into lysosomes.

Mechanistic analysis of drug release from tablets with membrane controlled drug delivery

The objective of this study was to receive detailed information on the mechanism of drug release from polyvinyl acetate (PVAc)/polyvinyl alcohol-polyethylene glycol graft copolymer (PVA-PEG) coated Propranolol HCl and Theophylline tablets. For this purpose the coating composition (PVAc/PVA-PEG: 90/10 and 80/20) and the amount of the coating layer have been varied. Due to its better solubility Propranolol HCl showed higher release rates than Theophylline. As expected, a higher percentage of the water soluble polymer accelerated drug release. Increased coating thickness led to amplified lag times of drug release. The water uptake of the tablets was quantified by gravimetric analysis. Furthermore, the microenvironment of the tablet core was monitored by EPR spectroscopy. For this purpose a hydrophilic EPR spin probe was incorporated into tablets. Surprisingly, despite a lag phase at the beginning and a controlled drug release over 24 h, the results of the EPR studies indicated an immediate water penetration through the coating layer into the tablet core. The water is able to solubilise the majority of water soluble compounds within minutes. The results obtained in this study demonstrate, that EPR is a powerful method to monitor the first steps of diffusion processes and the physicochemical state of coated dosage forms.

Development and validation of RP-HPLC-UV method for simultaneous determination of buparvaquone, atenolol, propranolol, quinidine and verapamil: A tool for the standardization of rat in situ intestinal permeability studies

A simple, sensitive and specific reversed phase high performance liquid chromatographic (RP-HPLC) method with UV detection at 251 nm was developed for simultaneous quantitation of buparvaquone (BPQ), atenolol, propranolol, quinidine and verapamil. The method was applicable in rat in situ intestinal permeability study to assess intestinal permeability of BPQ, a promising lead compound for Leishmania donovani infections. The method was validated on a C-4 column with mobile phase comprising ammonium acetate buffer (0.02 M, pH 3.5) and acetonitrile in the ratio of 30:70 (v/v) at a flow rate of 1.0 ml/min. The retention times for atenolol, quinidine, propranolol, verapamil and BPQ were 4.30, 5.96, 6.55, 7.98 and 8.54 min, respectively. The calibration curves were linear (correlation coefficient > or =0.996) in the selected range of each analyte. The method is specific and sensitive with limit of quantitation of 15 microg/ml for atenolol, 0.8 microg/ml for quinidine, 5 microg/ml for propranolol, 10 microg/ml for verapamil and 200 ng/ml for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and all the analytes were found to be stable. This method is simple, reliable and can be routinely used for accurate permeability characterization.

Novel generic UPLC/MS/MS method for high throughput analysis applied to permeability assessment in early Drug Discovery

A novel generic ultra performance liquid chromatography-tandem mass spectrometric (UPLC/MS/MS) method for the high throughput quantification of samples generated during permeability assessment (PAMPA) has been developed and validated. The novel UPLC/MS/MS methodology consists of two stages. Firstly, running a 1.5min isocratic method, compound-specific multiple reaction monitoring (MRM) methods were automatically prepared. In a second stage, samples were analyzed by a 1.5min generic gradient UPLC method on a BEH C18 column (50mmx2.1mm). Compounds were detected with a Waters Micromass Quattro Premier mass spectrometer operating in positive electrospray ionization using the compound-specific MRM methods. The linearity for the validation compounds (caffeine, propranolol, ampicillin, atenolol, griseofulvin and carbamazepine) typically ranges from 3.05nM to 12,500nM and the limits of detection for all generically developed methods are in the range between 0.61nM and 12nM in an aqueous buffer. The novel generic methodology was successfully introduced within early Drug Discovery and resulted in a four-fold increase of throughput as well as a significant increase in sensitivity compared to other in-house generic LC/MS methods.

Effects of hypoxia/reperfusion injury on drug disposition in the rat isolated perfused liver

1. Ischaemia-reperfusion injury is known to be associated with a range of functional and structural alterations in the liver. However, the effect of this injury on drug disposition is not well understood. The present study was designed to examine the effects of hypoxia/reperfusion on the disposition of glutamate and propranolol in the rat isolated perfused liver. Both glutamate and propranolol are mainly metabolised in the pericentral region of the liver. 2. Hypoxia/reperfusion was established using the slow flow-reflow method of perfusion in both anterograde and retrograde perfusion. Glutamate metabolism was measured by the recovery of [(14)C]-glutamic acid and [(14)C]-labelled metabolites in a single pass in both anterograde and retrograde perfusion in the presence of a steady state concentration of unlabelled glutamic acid. Propranolol disposition, mean transit time and normalized variance were assessed from the outflow concentration-time profile of unchanged [(3)H]-propranolol determined after a bolus injection of [(3)H]-propranolol using HPLC and liquid scintillation counting. 3. Hypoxia/reperfusion of livers did not affect oxygen consumption, but caused significant changes in enzyme release, lignocaine hepatic availability and bile flow. 4. Hypoxia/reperfusion did not affect the hepatic metabolism of glutamate to carbon dioxide or the hepatic extraction of propranolol. Small but significant changes were evident in the distribution parameters of mean transit time and vascular disposition for the hypoxic-ischaemic liver. 5. It is concluded that reperfusion injury induced by slow flow-reflow perfusion did not influence the extraction of glutamate or propranolol, but may have affected pericentral morphology and solute distribution.

Elastic liposomes mediated transdermal delivery of an anti-hypertensive agent: propranolol hydrochloride

One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present investigation ultradeformable lipid vesicles, that is, elastic liposomes were prepared incorporating propranolol hydrochloride for enhanced transdermal delivery. Elastic liposomes bearing propranolol hydrochloride were prepared by conventional rotary evaporation method and characterized for various parameters including vesicles shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, turbidity, and in vitro drug release. In vitro flux, enhancement ratio (ER), and release pattern of propranolol hydrochloride were calculated for transdermal delivery. In vivo study conducted on male albino rats (Sprague Dawley) was also taken as a measure of performance of elastic liposomal, liposomal, and plain drug solution. The better permeation through the skin was confirmed by confocal laser scanning microscopy (CLSM). Results indicate that the elastic liposomal formulation for transdermal delivery of propranolol hydrochloride provides better transdermal flux, higher entrapment efficiency, ability as a self-penetration enhancer and effectiveness for transdermal delivery as compared to liposomes.

Propranolol preparations on the Belgian market: a comparative study

Propranolol preparations formulated as immediate-release tablets and prolonged-release capsules were evaluated with different tests, including in vitro dissolution and assay with previously validated methods according to the guideline of the European network of Official Medicines Control Laboratories (OMCLs). All examined products complied with our requirements and those described in the European, British and the US Pharmacopoeia and consequently they can be considered as pharmaceutically equivalent.

Permeability of atenolol and propranolol in the presence of dimethyl sulfoxide in rat single-pass intestinal perfusion assay with liquid chromatography/UV detection

A simple and sensitive RP-HPLC-UV method was developed and validated for simultaneous determination of atenolol and propranolol and subsequently applied to investigate the effect of dimethyl sulfoxide in rat in situ intestinal permeability studies. Atenolol (400 microm) and propranolol (100 microm) were perfused in the small intestine of anaesthetized (pentobarbitone sodium 60 mg/kg, i.p.) male Sprague-Dawley rats either in the presence (1, 3 and 5%) or in the absence of dimethyl sulfoxide. There was no significant alteration (p > 0.05) in the permeability of atenolol and propranolol, which indicated there was no effect of various concentrations of dimethyl sulfoxide (1-5%) on the membrane integrity of the rat intestinal tissues. The analytical method was validated on a C(4) column with a mobile phase comprising ammonium acetate buffer (pH 3.5, 0.02 m) and acetonitrile in the ratio of 30:70 (v/v) at a flow rate of 1.0 mL/min. The validated method was found to be accurate and precise and stability studies were carried out at different storage conditions and both analytes were found to be stable. These findings are applicable for determining the absorbability of water-insoluble drugs and new chemical entities for the purpose of classifying them in the biopharmaceutical classification system.

Modeling the impact of direct phototransformation on predicted environmental concentrations (PECs) of propranolol hydrochloride in UK and US rivers

There is currently uncertainty on the persistence of active pharmaceutical ingredients (APIs) and on their depletion mechanisms in natural surface waters such as rivers, and hence predictions of their fate are often poor. In this study, a beta-adrenergic receptor, propranolol hydrochloride, was selected as a model API to explore the relative significance of direct phototransformation as a potential removal process of hydrophilic APIs in rivers. Phototransformation kinetics of propranolol was measured under simulated solar irradiation in the laboratory, which were then converted to the kinetics applicable in UK and US rivers. The effects of light intensity, light penetration, river size and flow were examined. The extrapolated phototransformation half-lives were applied in the river catchment models of GREAT-ER and PhATE. Results demonstrated that direct phototransformation significantly reduced the predicted environmental concentrations of propranolol in the water phase. Predicted reductions of mean concentrations in the River Aire (UK) were 27% in summer and 3% in winter; and for the US rivers simulated, reductions were 28-68% in summer and 11-41% in winter. The highest reductions were predicted for long rivers with low turbidity and low flow conditions.

Pravastatin reverses the down-regulating effect of inflammation on β-Adrenergic receptors: A disease–drug interaction between inflammation, pravastatin, and propranolol

Inflammatory conditions reduce the potency to prolong the PR interval of certain cardiovascular drugs including propranolol, sotalol, and verapamil in rats and humans despite elevated plasma drug concentrations. We tested whether pravastatin restores altered action and disposition of propranolol as well as inflammatory mediators concentrations in the Pre-Adjuvant Arthritis (Pre-AA) Sprague-Dawley rat model. Rats [Healthy/Placebo, Arthritis/Placebo, Healthy/Statin, and Arthritis/Statin groups (n=14-16/group)] received Mycobacterium butyricum on day 0 followed by 6 mg/kg pravastatin or placebo twice daily during days 4-8. PR-interval response to 25 mg/kg oral propranolol was measured on days 0, 4 and 8. On day 8, blood samples were collected for interferon-gamma, interleukin-10, C-reactive protein, and nitrite measurements. Propranolol enantiomer pharmacokinetics were delineated using another 4 groups (healthy n=5, Pre-AA n=9) on day 8. Pre-AA significantly reduced propranolol response despite a 10-fold increase in concentrations. Pravastatin restored the response but not the drug concentrations. Area under the % effect-time curve (% min) was 714+/-214 in Healthy/Placebo, 256+/-249 in Arthritis/Placebo, 1534+/-367 in Healthy/Statin, and 1713+/-393 in Arthritis/Statin. While pravastatin reduced elevated serum interferon-gamma concentration in the Pre-AA model, it did not influence other biomarkers. Pravastatin restores response to propranolol in inflamed rat but has no effect on the elevated propranolol concentrations. This was associated with lower serum interferon-gamma concentrations.

Statistical optimisation of the mucoadhesivity and characterisation of multipolymeric propranolol matrices for buccal therapy

A Box-Behnken experimental design was employed to optimise a polymeric blend for the preparation of propranolol HCl matrices with maximum mucoadhesivity and was thereafter modified for achieving controlled drug release. The quantitative effects of the polymers used i.e. poly(acrylic acid) (PAA) and poly(vinyl pyrrolidone) (PVP) on mucoadhesion could be predicted using polynomial equations. A formulation of 20% PAA, 20% CMC and 20% PVP was identified for maximising mucoadhesivity and obtaining a controlled drug release profile. Reproducibility of the optimal formulation in terms of mucoadhesivity and controlled drug release was confirmed. The optimal formulation was characterised in terms of mucoadhesivity, release kinetics, swelling/erosion, hydration dynamics and surface pH. From the model fitting analyses, drug release was found to be diffusion, polymeric relaxation and erosion based with the former two being more dominant over erosion. This was in agreement with the erosion and swelling studies which showed swelling and erosion occurring in the tablet matrix. Textural profiling showed initial rapid hydration, which could be beneficial for enhanced mucoadhesivity. Surface pH of the multipolymeric matrices was similar to salivary pH and did not show extremes in changes over the test period. The optimal preparation of multipolymeric propranolol matrices identified in this study shows potential for buccal administration.

Anthranoid laxatives influence the absorption of poorly permeable drugs in human intestinal cell culture model (Caco-2)

Interactions between widely used anthranoid laxatives and other simultaneously administered drugs are not known. In this paper, the influence of rhein, danthron, sennidins A/B, sennosides A/B, and senna leaf infusion was investigated on the permeability of furosemide, ketoprofen, paracetamol, propranolol, verapamil, digoxin, and Rhodamine 123 across Caco-2 monolayers. The effects on monolayer integrity ([(14)C]mannitol permeability, TEER) were also determined. The in vitro absorption of highly permeable drugs was not strongly affected during co-administration of the laxatives. Furosemide permeability was enhanced by rhein and danthron (3.6 and 3.0-fold), which may partly be due to opening of the paracellular spaces and/or effects on active efflux. However, the secretory permeability of digoxin and Rho 123 was not strongly affected by rhein and danthron, suggesting that inhibition of MDR1 was not responsible for the increased permeation of furosemide. The absorptive permeability of digoxin was decreased by rhein and danthron, offering evidence for effects on apical membranes. The effects on monolayer integrity were detectable, but reversible. According to presented experiments, daily use of laxatives with well-absorbing drugs would seem unlikely to affect drug permeability, but the effects on the absorption of poorly permeable drugs cannot be excluded.

Radical cross-linked albumin microspheres as potential drug delivery systems: preparation and in vitro studies

The aim of this research is the preparation of acryloylated bovine serum albumin microspheres and the evaluation of their employment in drug delivery. The influence of preparation parameters on albumin microspheres and the chemicophysical properties of loaded drugs were investigated. In particular, we focused our attention on acylation albumin degree, amount of acryloylated albumin against comonomer in the polymerization step, and finally the release profile. We considered on the interaction drug-matrix, the fuctionalization degree of albumin, and the water affinity of matrix.

Automated measurement of permeation and dissolution of propranolol HCl tablets using sequential injection analysis

Aim of this study was to automate sampling and quantification of the previously described apparatus for combined determination of dissolution and permeation through Caco-2 monolayer by means of sequential injection analysis (SIA). Native fluorescence of propranolol HCl in Krebs-Ringer buffer (KRB) was used for quantification. Sampling was done at three different locations within the apparatus at a high sampling frequency (approximately 60 h(-1)). Injection volume delivered to the fluorescence detector was 50 microL for permeation monitoring and 25 microL for dissolution monitoring. Linear regression for 50 microL injection yielded a detection limit calculated as 0.04 microg mL(-1) of propranolol HCl in KRB (R(2)>0.999). However, linearity for dissolution monitoring was not given for the complete range of concentrations and first order polynomial calibration was established (R(2)>0.9999). To conclude, the SIA system was able to monitor simultaneously dissolution and permeation of the immediate release propranolol HCl tablets and the authors succeeded in automating the apparatus for combined measurement of dissolution and permeation. In addition, the obtained data was consistent with data obtained by manual sampling followed by HPLC analysis.

Induction of Propranolol Metabolism by Ginkgo biloba Extract EGb 761 in Rats

Ginkgo biloba is one of the most popular herbal medicines in the world, due to its purported pharmacological effects, including memory-enhancing, cognition-improving, and antiplatelet effects. When used in the elderly, Ginkgo has a high potential for interactions with cardiovascular drugs. This study aimed to investigate the effects of the standard Ginkgo biloba extract (EGB 761) treatment on the pharmacokinetics of propranolol and its metabolism to form N-desisopropylpropranolol (NDP) in rats. We also examined the activity and expression of cytochrome P450 (CYP) 1A and other CYPs in rats treated with EGb 761 at 10 and 100 mg/kg/day for 10 days. A single oral dose of propranolol (10 mg/kg) was administered on day 11 and the concentrations of both propranolol and NDP were determined using validated liquid chromatography-mass spectrometry (LC-MS) methods. The levels of mRNA and protein of various CYPs were determined by RT-PCR and Western blotting analysis, respectively. Pretreatment of EGb 761 at 100 mg/kg, but not 10 mg/kg, for 10 days significantly reduced the area under the plasma concentration-time curve (AUC) and maximum plasma concentration (Cmax) of propranolol, whereas those values of NDP were significantly increased. CYP1A1, 1A2, 2B1/2, and 3A1 activities and gene expression in the rat liver were significantly increased in a dose-dependent manner by pretreatment with EGb 761. The ex-vivo formation of NDP in liver microsomes from rats pretreated with EGb 761 was markedly enhanced. The formation of NDP from propranolol in liver microsomes was significantly inhibited by alpha-naphthoflavone (ANF, a selective CYP1A2 inhibitor), but not by quinidine (a CYP2D inhibitor). These results indicated that EGb 761 pretreatment decreased the plasma concentrations of propranolol by accelerated conversion of parental drug to NDP due to induction of CYP1A2. EGb 761 pretreatment also significantly induced CYP2B1/2 and CYP3A1, suggesting potential interactions with substrate drugs for these two enzymes. Further study is needed to explore the potential for gingko-drug interactions and the clinical impact.

Uptake and intracellular binding of lipophilic amine drugs by isolated rat hepatocytes and implications for prediction of in vivo metabolic clearance

The hepatic uptake of imipramine and propranolol was investigated after incubation with isolated rat hepatocytes over a wide concentration range (0.04-400 microM). The cell-to-medium concentration ratio (K(p)) was concentration-dependent and could be described using a two-site binding model incorporating a high affinity/low capacity site and a linear component for a site which was apparently not saturated. Maximum (at 0.04 microM) and minimum K(p) values (at 400 microM) were 360 and 280, and 110 and 70 for imipramine and propranolol, respectively. During these incubations, metabolism was inhibited using aminobenzotriazole (an irreversible inhibitor of cytochrome P450). Pretreatment of cells either by freeze-thawing or with saponin (which permeabilizes the plasma membrane) eliminated the saturable process. The saturable uptake process of imipramine was also inhibited by 18 other lipophilic amine drugs (including propranolol). This uptake component may involve membrane transporter(s), whereas the nonsaturable component probably represents partition into the phospholipid component of membranes. Propranolol was further investigated to determine the impact of high K(p) values on hepatocellular clearance. The area under the curve for propranolol concentrations in the total incubate (medium including the cells) from the depletiontime profile was substantially greater than the corresponding area under the curve for the drug concentration in the extracellular medium, and this difference approximated the nonsaturable uptake component. It is concluded that the clearance of propranolol in isolated hepatocytes is not rate-limited by hepatic uptake and is directly proportional to unbound drug concentration, being independent of the higher K(p) value.

Physicochemical Characterization and Evaluation of Buccal Adhesive Patches Containing Propranolol Hydrochloride

Buccal adhesive patches containing 20 mg of propranolol hydrochloride were prepared using solvent casting method. Chitosan was used as a natural bioadhesive polymer. Patches were prepared at different ratios of PVP K-30 and evaluated for various physicochemical characteristics such as weight variation, drug content uniformity, folding endurance, surface pH, ex-vivo mucoadhesive strength, ex-vivo residence time, in vitro drug release and in vitro buccal permeation study. Patches exhibited sustained release over a period of 7 hours. The mechanism of drug release was found to be Non-Fickian diffusion. Addition of PVP K-30 generally enhanced the releasing rate. The ex-vivo mucoadhesive strength was performed using sheep buccal mucosa on modified physical balance. Optimized patches (batch F4) showed satisfactory bioadhesive strength (9.6 degrees 2.0 gram) and ex vivo residence time (272 degrees 0.25 minutes). Swelling index was proportional to PVP K-30. The surface pH of all batches was within satisfactory limit (7.0+/-1.5) and hence patches would not cause irritation in the buccal cavity. Good correlation was observed between in vitro drug release and in vitro drug permeation with correlation coefficient of 0.9364. Stability of optimized patches was performed in natural human saliva showed that both drug and dosage forms were stable in human saliva.

Composite membrane of bacterially-derived cellulose and molecularly imprinted polymer for use as a transdermal enantioselective controlled-release system of racemic propranolol

A composite membrane for transdermal delivery of S-propranolol enantiomer was developed based on the controlled pore functionalization of bacterial cellulose membranes using a molecularly imprinted polymer (MIP) layer synthesis. The reactive pore-filling of an asymmetric porous cellulose membrane with a MIP thin-layer was effected using a silanized coupler as an additional anchor for the MIP. MIP thin-layers with specific binding sites for S-propranolol were synthesized by copolymerization of methacrylic acid with a cross-linker, ethylene glycol dimethacrylate in the presence of S-propranolol as the template molecule and the latter was subsequently extracted. Selective transport of S-propranolol through the MIP composite membrane was obtained, although this was determined mostly by the parent cellulose membrane with some ancillary contributory effect from the MIP layer. In addition, an enantioselectivity in the transport of propranolol prodrug enantiomers was found, suggesting that the shape and functional groups orientation, which are similar to that of the print molecule were essential for enantiomeric recognition of the MIP composite membrane. The enantioselectivity of S-MIP membranes was also shown when the release of propranolol enantiomers was studied in vitro using rat skin, with racemic propranolol contained in the donor compartment. The composite membrane of bacterially-derived cellulose and molecularly imprinted polymer may have great potential for use as a transdermal enantioselective controlled-release system for racemic propranolol.

Effective on-line purification for cationic compounds in rat bile using a column-switching LC technique

An on-line purification method for cationic compounds and their metabolites in rat bile was investigated using a column-switching technique. 8-Hydroxyquinoline and its glucuronide were used as test compounds. Bile samples were injected directly into the system and successful on-line extraction with high purification efficiency for analytes was achieved using two-dimensional extraction LC; that is, reversed-phase chromatography followed by cation-exchange chromatography. After removal of the endogenous component by extraction LC, chromatographic separation of the target analyte was performed on an analytical ODS column, followed by identification using UV detection. The quantitative ability of the method was evaluated on the basis of injection repeatability, linearity and accuracy. This novel method was also applied to LC/MS analysis in order to characterise the pharmacokinetics of propranolol in rats, and the metabolites were successfully identified.