Effects of nano-sizing on lipid bioaccessibility and ex vivo bioavailability from EPA-DHA rich oil in water nanoemulsion.

The physiological efficacy of nutraceuticals is dependent on their physicochemical nature and bioavailability across biological barriers. In the present work, effects of nano-sizing of emulsion-based delivery vehicle on the bioavailability of polyunsaturated fatty acids rich fish oil have been investigated via three-step experimental design; ex vivo rat everted intestinal sac model, cellular lipid uptake and the bioactivity in rat PBMCs. Nanoemulsion in comparison to the conventional emulsion has shown significant higher rate of uptake of polyunsaturated fatty acids in three segments of small intestine. The time-kinetics of such uptake was correlated with appearance of short-chain fatty acids in basal side of the everted sac. The bioavailability of the formulated fish oil and its inhibitory response against lipopolysaccharide-induced nitric oxide production in rat PBMCs were positively correlated. This formulation with nano-sized droplets can be utilized as smart delivery vehicles for designing oral therapies in future.

Pharmacokinetics and tissue distribution profile of icariin propylene glycol-liposome intraperitoneal injection in mice.

OBJECTIVES: The pharmacokinetics and tissue distribution of icariin propylene glycol-liposome suspension (ICA-PG-liposomes) have been investigated. METHODS: ICA-PG-liposomes or ICA-PG-solution were prepared and intraperitoneally injected to mice. Morphology and size distribution of ICA-PG-liposomes were observed by transmission electron microscopy (TEM) and laser particle sizer. Plasma and tissues were collected at different times after intraperitoneal injection and icariin concentrations were determined by HPLC. KEY FINDINGS: From TEM, ICA-PG-liposomes showed spherical vesicles with a mean particle size of 182.4 nm. The encapsulation efficiency of ICA-PG-liposomes reached 92.6%. Pharmacokinetics of ICA-PG-liposomes displayed the three open compartments model. ICA-PG-liposomes enhanced icariin absorption from the abdominal cavity, prolonged mean retention time (MRT((0-t))), increased area under curve (AUC((0-t))) and maximum concentration in plasma. Compared with ICA-PG-solution, ICA-PG-liposomes resulted in larger amounts of icariin being distributed into spleen (60.38% total icariin), liver (16.68%), lung (6.21%), kidney (4.64%), heart (1.43%) and brain (1.83%). AUC((0-t)) values in most tissues (except lung) of mice administered ICA-PG-liposomes were higher than those administered ICA-PG-solution, while Clearance in most tissues (except brain and lung) decreased. The MRT((0-t)) values of ICA-PG-liposomes in all tissues and half lives of most tissues (except brain) were prolonged. From Targeted efficiency and relative uptake data, the spleen was the target tissue of the ICA-PG-liposomes. CONCLUSIONS: ICA-PG-liposomes changed the pharmacokinetic behaviour and enhanced icariin distribution in tissues. With nanometer size, high encapsulation efficiency and improved pharmacokinetics, ICA-PG-liposomes might be developed as promising carriers for icariin injection.

Vehicle-dependent disposition kinetics of fluoranthene in Fisher-344 rats.

The objective of this study was to evaluate how the vehicles of choice affect the pharmacokinetics of orally administered Fluoranthene [FLA] in rats. Fluoranthene is a member of the family of Polycyclic Aromatic Hydrocarbon chemicals. Fluoranthene exposure to humans may occur as a result of cigarette smoking, consumption of contaminated food and water, heating woods in stoves and boilers, industrial sources such as coal gasification, carbon and graphite electrode manufacturing. Adult male Fisher-344 rats were given single oral doses of 25 and 50 microg/kg FLA in tricaprylin, peanut oil, cod liver oil, Tween 80/isotonic saline (1:5) and 2% Alkamuls-EL620 through gavage. After administration, the rats were housed individually in metabolic cages and sacrificed at 2, 4, 6, 8, 10 and 12 hours post FLA exposure. Blood, lung, liver, small intestine, adipose tissue samples, urine, and feces were collected at each time point. Samples were subjected to a liquid-liquid extraction using methanol, chloroform, and water. The extracts were analyzed by a reverse-phase HPLC, equipped with a fluorescence detector. The results revealed a dose-dependent increase in FLA concentrations in plasma and tissues for all the vehicles used. Plasma and tissue FLA concentrations were greater for peanut oil; cod liver oil, and tricaprylin vehicles compared to Alkamuls (p < 0.05), and Tween 80/isotonic saline (1:5). Most of the FLA administered through peanut oil, cod liver oil and tricaprylin was cleared from the body by 8 hours (90%) and 12 hours (80%) post administration for the 25 microg/kg and 50 microg/kg dose groups, respectively. With both doses employed, the metabolism of FLA was highest when cod liver oil was used as a vehicle and lowest in vehicles containing detergent/water [cod liver oil > peanut oil > tricaprylin > alkamuls > Tween 80/isotonic saline (1:5)]. These findings suggest that uptake and elimination of FLA is accelerated when administered through oil-based vehicles. The low uptake of FLA from Alkamuls and Tween 80/isotonic saline may have been a result of the poor solubility of the chemical. In summary, our findings reiterate that absorption characteristics of FLA were governed by the dose as well as the dosing vehicle. The vehicle-dependent bioavailability of FLA suggests a need for the judicious selection of vehicles in evaluating oral toxicity studies for risk assessment purposes.

In vivo and in vitro characterization of the novel antiarrhythmic agent SSR149744C: electrophysiological, anti-adrenergic, and anti-angiotensin II effects.

SSR149744C (SSR, 2-butyl-3-[4-[3-(dibutylamino)pro-pyl]benzoyl]-1-benzofuran-5-carboxylate isopropyl fumarate), is a new non-iodinated benzofuran derivative. The aim of this study was to evaluate in vivo its electrophysiological, hemodynamic, and anti-adrenergic properties and to determine its mechanism of action using in vitro studies. In chloralose-anesthetized dogs, SSR149744C (1-10 mg/kg i.v.) prolonged the sinus cycle length, A-H interval, Wenckebach cycle length, atrial effective refractory period (ERP), and atrio-ventricular node ERP in a dose-dependent manner without change of ventricular ERP and HV, QRS, or QTc intervals. Arterial blood pressure and ventricular inotropism were slightly decreased. SSR149744C, which has no or low affinity for alpha 1 and beta 1 adrenergic and angiotensin II AT1 receptors, reduced isoproterenol-induced tachycardia and phenylephrine- or angiotensin II-induced hypertension in anaesthetized dogs. In guinea pig papillary muscle, SSR149744C did not modify the resting potential, action potential amplitude and duration, but reduced the dV/dt max of the depolarization phase in a frequency-dependent manner. In isolated guinea pig cardiomyocytes and transfected CHO cells, SSR149744C (0.01-30 microM) inhibited several potassium currents: IKr (IC50 approximately 10 microM), IKs (IC50 approximately 30 microM), IK(ACh) (IC50 = 0.09 microM), and IKv1.5 (IC50 = 2.7 microM), the L-type calcium current: ICa(L) (IC50 approximately 5 microM) and also the amplitude of [Ca2+]i transient and cell shortening. Therefore, SSR149744C appears to have a multifactorial mechanism of action, which combines the blockade of several ion channels with the inhibition of responses of alpha 1 and beta 1 adrenergic as well as AT1 receptor stimulation. Like amiodarone, SSR149744C possesses the pharmacological effects of class I, II, III, and IV antiarrhythmic agents, which may confer upon this new drug a strong antiarrhythmic potential without ventricular proarrhythmia and iodine-related amiodarone-like side-effects.

Simple rules defining the potential of compounds for transdermal delivery or toxicity.

PURPOSE: Simple rules based on readily accessible physicochemical properties enable identification of solutes that penetrate skin very slowly or rapidly. METHODS: Literature in vitro maximal flux values (Jmax) across human skin were collected for 87 penetrants. Penetrants were assigned as "good" (Jmax > 10(-5.52) mole x cm(-2) x h(-1)), "bad" (Jmax < 10(-8.84) mole x cm(-2) x h(-1)) or "intermediate" based on mean +/- 1SD. The feasibility of using readily available physicochemical properties, such as molecular weight (MW), melting point (MP, degrees K), octanol-water partition coefficient (K), water solubility (S, molarity), number of atoms available for H-bonding (HB), in assigning solutes was examined. RESULTS: Good penetrants had MW < or = 152, log S > -2.3, HB < or = 5, log K < 2.6, MP < or = 432. Bad penetrants had MW > 213, log S < -1.6, HB > or = 4, log K > 1.2, MP > or = 223. Discriminant analysis using MW, HB, log K correctly assigned 70% of compounds. Individual success rates were good (88%), intermediate (58%), bad (93%). Aqueous Jmax data for 148 test solutes were used for validation. Discriminant analysis assigned 76% of compounds, with individual rates of good (76%), intermediate (67%), and bad (97%). No good penetrants were misclassified as bad or vice versa. CONCLUSIONS: These rules enable rapid screening of potential drug delivery candidates and environmental exposure risks.

Transdermal delivery system for zidovudine: in vitro, ex vivo and in vivo evaluation.

The objective of this study was to prepare a transdermal delivery system (TDS) for zidovudine (AZT) with a combination of menthol and oleic acid as penetration enhancers incorporated in hydroxypropyl methylcellulose, and to evaluate ex vivo as well as in vivo permeation across rat skin. It was found that AZT in gel formulation was stable in both refrigerated as well as accelerated stability conditions for 3 months and further, the gel did not significantly retard the permeability of AZT across the skin in comparison with solution formulation. Ex vivo steady state flux of AZT across rat skin from gel was 2.26 mg cm(-2) h(-1), which is sufficient to achieve therapeutic plasma concentrations. Intravenous pharmacokinetic parameters of AZT in rats were determined and used together with ex vivo flux data to generate theoretical plasma profiles of AZT and compared with plasma concentrations achieved after application of TDS. Further, steady state plasma concentrations of drug following multiple applications of TDS were determined and good correlations between ex vivo and in vivo data were observed. In addition, the combination of penetration enhancers used at 2.5% w/w in this study proved efficient in achieving sufficient enhancement in the transdermal permeability of AZT across rat skin with reduced skin irritation potential when compared with individual penetration enhancers at higher concentrations.

Commonly used surfactant, Tween 80, improves absorption of P-glycoprotein substrate, digoxin, in rats.

Tween 80 (Polysorbate 80) is a hydrophilic nonionic surfactant commonly used as an ingredient in dosing vehicles for pre-clinical in vivo studies (e.g., pharmacokinetic studies, etc.). Tween 80 increased apical to basolateral permeability of digoxin in Caco-2 cells suggesting that Tween 80 is an in vitro inhibitor of P-gp. The overall objective of the present study was to investigate whether an inhibition of P-gp by Tween 80 can potentially influence in vivo absorption of P-gp substrates by evaluating the effect of Tween 80 on the disposition of digoxin (a model P-gp substrate with minimum metabolism) after oral administration in rats. Rats were dosed orally with digoxin (0.2 mg/kg) formulated in ethanol (40%, v/v) and saline mixture with and without Tween 80 (1 or 10%, v/v). Digoxin oral AUC increased 30 and 61% when dosed in 1% and 10% Tween 80, respectively, compared to control (P < 0.05). To further examine whether the increase in digoxin AUC after oral administration of Tween 80 is due, in part, to a systemic inhibition of digoxin excretion in addition to an inhibition of P-gp in the GI tract, a separate group of rats received digoxin intravenously (0.2 mg/kg) and Tween 80 (10% v/v) orally. No significant changes in digoxin IV AUC was noted when Tween 80 was administered orally. In conclusion, Tween 80 significantly increased digoxin AUC and Cmax after oral administration, and the increased AUC is likely to be due to an inhibition of P-gp in the gut (i.e., improved absorption). Therefore, Tween 80 is likely to improve systemic exposure of P-gp substrates after oral administration. Comparing AUC after oral administration with and without Tween 80 may be a viable strategy in evaluating whether oral absorption of P-gp substrates is potentially limited by P-gp in the gut.

Three vehicle formulations for melagatran, a direct thrombin inhibitor, evaluated in a vena cava thrombosis model in the rat.

BACKGROUND: The objective of this study was to investigate whether the use of a depot formulation would enhance the antithrombotic effect of the direct thrombin inhibitor melagatran. METHODS AND RESULTS: In a rat venous thrombosis model, animals were openly randomized to receive subcutaneously (s.c.) either vehicle (saline, cyclodextrin or poloxamer) or melagatran (0.5 microM/kg) dissolved in vehicle. An additional injection of cyclodextrin or poloxamer was given at another site to investigate whether the vehicle itself had any additional effect. All injections were given 30 min before induction of thrombus formation. Thrombus formation was induced by ferric chloride, together with stenosis of the caval vein, during a short period of inhalation anaesthesia. Five hours later the thrombi were harvested and their wet weight determined. Thrombus size was comparable across the vehicle-only groups. The antithrombotic effects of melagatran in saline or poloxamer were comparable while melagatran in cyclodextrin was less effective. The effects of melagatran in saline, cyclodextrin or poloxamer were not enhanced by additional cyclodextrin or poloxamer. Thrombin time (TT) and activated partial thromboplastin time (aPTT) at the end of the experiment were prolonged to a greater extent in the groups receiving melagatran in cyclodextrin or poloxamer compared with those receiving melagatran in saline. CONCLUSION: In this vena cava thrombosis model, no enhanced antithrombotic effect was observed with melagatran given as a s.c. depot formulation in cyclodextrin or poloxamer compared with that in saline.

Long-circulating emulsions (oil-in-water) as carriers for lipophilic drugs.

PURPOSE: Rapid clearance of parenterally administered oil-in-water emulsions from blood by the reticuloendothelial system (RES), mainly macrophages of the liver and spleen, has been one of the major obstacles for delivering lipophilic drugs to cells other than those in the RES. The purpose of this study therefore is to overcome this problem and develop emulsions that will have prolonged blood circulation time. METHODS: A series of amphipathic polyethylene-glycol (PEG) derivatives have been included as co-emulsifier into emulsions composed of Castor oil and phosphatidylcholine. The effect of amphipathic PEG on reducing the RES uptake and prolonging the blood circulation of the emulsion particles has been tested in vivo using mice as an animal model. RESULTS: Inclusion of PEG derivatives such as Tween-80 or dioleoyl N-(monomethoxy-polyethyleneglycol succinyl)phosphotidylethanolamine (PEG-PE) into emulsions composed of Castor oil and phosphatidylcholine decreases the RES uptake and increases blood residence time of the emulsions. The activity of PEG derivatives in prolonging the circulation time of emulsions depends on the PEG chain length (PEG2000 > PEG5000 > PEG1000, Tween-80) and the PEG density on emulsion surface. CONCLUSIONS: Inclusion of amphipathic PEG as emulsifier into oil-in-water emulsions is a very effective method to prolong the blood half life of the emulsions. Emulsions with long circulating half life in blood should be very useful as a delivery vehicle for lipophilic drugs.

Pharmacokinetics of parenteral 13-cis-retinoic acid formulations in rats.

The pharmacokinetics of three 13-cis-retinoic acid formulations were studied after intraperitoneal (ip) administration to rats. Rats were given ip injections of 2.5 mg of 13-cis-retinoic acid per 360 g of body weight; the drug was administered as an alkaline solution, suspended in corn oil, or as a mixture with polysorbate 80. The alkaline solution was also given intravenously (iv) via the tail vein as a control. The mean elimination rate constant, calculated from data from iv administration, was 0.72 +/- 0.088 h-1 (r = 0.988). The peak concentration in plasma and the time to reach this maximum were 14 mg/L and 0.5 h, 22 mg/L and 2 h, and 10 mg/L and 1 h for the drug administered as an alkaline solution, suspended in corn oil, and as a mixture with polysorbate 80, respectively. The areas under the concentration-time curve (concentration in plasma versus time) were 34.9 +/- 8.78 mg.h/L for the iv dose and 34.1 +/- 9.97, 62.4 +/- 32.3, and 25.9 +/- 12.0 mg.h/L for the ip doses of alkaline solution, suspension in oil, and mixture with polysorbate 80, respectively. Because of the rapid increase of concentration in plasma, which is identical to that of the iv profile, and the ease of its handling and preparation, the ip administered alkaline solution is the preferable formulation.