Solution Dosage Form Research Articles

Stability and Antibiotic Potency Improvement of Levofloxacin by Producing New Salts with 2,6- and 3,5-Dihydroxybenzoic Acid and Their Comprehensive Structural Study

Recently, solid-state engineering has become a promising approach to improving the stability and potency of antibiotics. Levofloxacin (LF) is a broad-spectrum fluoroquinolone antibiotic marketed in solid and solution dosage forms. However, this substance forms solid hydrates under ambient conditions and degrades due to lighting, which may change its solid properties and dose. In addition, resistance cases have been reported due to long-time antibiotic usage. This research aims to allow LF to react with antioxidant dihydroxybenzoic acid (DHBA), which has low antimicrobial activity, to produce a more stable compound under water and lighting conditions and improve LF's potency. The experiment begins with a screening to select potential DHBA isomers that can react with LF and predict the stoichiometric ratio using phase diagrams, which show that 2,6-DHBA and 3,5-DHBA are prospective antioxidants that can react with LF in a (1:1) molar ratio. Multicomponent systems are prepared by dissolving the LF-DHBA mixture in (1:1) ethanol-methanol (95% grade) and evaporating it. Then, the new solid phase formation is confirmed by thermal analysis and powder X-ray diffractometry. Next, infrared spectrophotometry and neutron magnetic resonance analyses are used to identify the LF-DHBA's interactions. Finally, single-crystal X-ray diffractometry is used to solve the three-dimensional structure of the multicomponent system. We then conduct a hygroscopicity and stability test followed by a lighting and potency test using the microdilution method. Our data reveal that both reactions produce salts, which are named LF-26 and LF-35, respectively. Structurally, LF-26 is found in an anhydrous form with a triclinic crystal packing, while LF-35 is a hemihydrate in a monoclinic system. Afterward, both salts are proven more stable regarding water adsorption and UV lighting than LF. Finally, both multicomponent systems have an approximately two-fold higher antibiotic potency than LF. LF-26 and LF-35 are suitable for further development in solid and liquid dosage formulations, especially LF-35, which has superior stability compared with LF-26.

Extraction and Formulation of hydrolyzed-wool keratin solution for hair growth

Hair growth is controlled by hair Follicles which show patterns of cyclic activity with periods of active growth and hair production (anagen), apoptosis-driven involution (catagen) and relative resting (telogen). These transformations are regulated by different variations like endocrine, vascular, neural, age and nutritional. Keratin biomaterial has been used in regenerative medicine owing to its in-vivo and in-vitro biocompatibility. The present study aimed at extracting keratin from wool by sulfitolysis, filtration by dialysis tube and freeze drying. Qualitative analysis of the keratin extract powder ensured the presence of cysteine, Keratin powder formulated as solution dosage form and pharmaceutically evaluated, Keratin extract was topically applied on the synchronized depilated dorsal skin of telogenic 4 mice and promoted hair growth by changing Hair growth initiation and completion time and quality of hair result, in wool keratin extract solution-treated groups hair growth initiation and completion time reduced and the hair result was hard, long, thick and healthy. Besides, that the keratin extract solution was a safe agent for topical administration, our study demonstrated that keratin extract stimulating hair growth by inducing the growth phase. The topical application of keratin extract may represent a promising biomaterial for the management and applications of hair follicle disorder.

Enhanced anti-cataract effect of microemulsion containing Cineraria maritima: Formulation, optimization and in vivo evaluation

Cineraria maritima (CM) has a long history in Homeopathy for its immensely prescribed use in the treatment of cataracts throughout the globe. However, the commercially available solution dosage form of CM is primarily limited by its low efficiency. Therefore, the objective of this study was to develop an effective dosage form of CM to enhance its anti-cataract effect. CM-loaded microemulsion formulation was developed and optimized using ethyl oleate as oil, tween 80, and span 20 as Smix by using the water titration method. For the physicochemical characterization of extract-loaded microemulsion formulations, the identification of a marker compound was done by the HPLC technique. In- vitro characterization and ex-vivo evaluations of prepared formulations were carried out to determine the best formulation. The selected formulation (MEF1) was subjected to in-vivo anti-cataract and ocular irritation studies in the rabbit model and compared with a marketed aqueous formulation as control. The in vivo data demonstrated greater efficacy of microemulsion over-marketed formulation. The study results showed the promising anti-cataract effect of prepared microemulsion indicating its prospective to be used in the treatment of cataracts.

Eudragit® RL in 2-pyrrolidone as antisolvent-based in-situ forming matrix

Eudragit® RL (ERL) is pH independent copolymer. ERL is high permeability polymer with sustained released function; therefore, ERL is interesting polymer for the periodontal pocket drug delivery. The doxycycline hyclate (DH)-incorporated ERL-based in-situ forming matrix (ISF) was fabricated for intra-periodontal route employing 2-pyrrolidone (PYR) as a solvent. The various ERS concentrations in range of 10 to 25% w/w comprising 5% w/w DH in PYR were prepared as solution dosage forms. The viscosity of prepared formulations was polymeric concentration dependent (121 to 2134 cPs) with Newtonian-flow behavior. For 10, 15 and 20% w/w ERL solutions, there was no complete matrix formation after contact phosphate buffer solution pH 6.8 whereas the opaque solid matrix was apparently formed for 25% w/w ERL solution. Therefore, in situ phase separation of 25% w/w ERL solutions was achieved. The time to reach more than 80% drug release were 10, 24, 24 and 48 h for ISFs comprising 10, 15, 20 and 25% w/w ERL, respectively. Thus, ISFs containing ERL dissolved in PYR showed a potential system to deliver DH by intra-periodontal route of administration. By comparison, the 25% w/w ERL solution were most suitable for antisolvent-based ISF development.

Pharmacokinetics, distribution and efficacy of triptolide PLGA microspheres after intra-articular injection in a rat rheumatoid arthritis model

The UPLC-MS/MS method was established with good precision, accuracy and stability to determine the concentrations of TPL in biological samples, such as heart, liver, spleen, lung, kidney, plasma and joint. After being made into microspheres, TPL can stay in the joint tissue for a long time, further reducing the number of times joint cavity administration, and its sustained release effect was significantly improved compared with the solution dosage form. The pharmacokinetic parameters, such as AUC(0–t), AUC(0–∞), T 1/2, T max, MTR(0–t), and MTR(0–∞) of the TPL-PLGA-MS group were significantly increased compared with those of the solution group. The microsphere preparation could significantly slow the release rate of the drug from the joint cavity. TPL-PLGA-MS can significantly reduce the expression of inflammatory factors such as IL-1, IL-6, TNF-α and hs-CRP. TPL-PLGA-MS for articular cavity injection has potential as a new preparation for the treatment of RA.

An Overview on Recent Advances in Pharmaceutical Suspensions

The suspension is a biphasic liquid or semi-solid dosage form where the finely divided insoluble solid drug particles are homogeneously dispersed in a liquid or semi-solid medium. The solid drug particles act here as the dispersed phase and the liquid or the semi-solid as the dispersion medium. The particle diameter in a suspension is usually greater than 0.5 µm. However, it is difficult and also impractical to impose a sharp boundary between the suspensions and the dispersions having finer particles. Suspensions are an important class of pharmaceutical dosage forms. The advantages of suspension dosage forms include effective dispensing of hydrophobic drugs; avoidance of the use of cosolvents; masking of unpleasant taste of certain ingredients; offering resistance to degradation of drugs due to hydrolysis, oxidation or microbial activity; easy swallowing for young or elderly patients; and efficient intramuscular depot therapy. In addition, when compared to solution dosage forms, relatively higher concentration of drugs can be incorporated into suspension products. The present review provides an overview of various aspects of suspensions such as classification of suspensions, theories of suspensions, various suspending agents, formulations aspects of suspensions, stability of suspensions and recent research work that is being carried on suspensions. Keywords: Suspensions, suspending agents, flocculated, Stability.

Design of Topical Ocular Ciprofloxacin Nanoemulsion for the Management of Bacterial Keratitis.

Bacterial keratitis (BK) is a critical ocular infection that can lead to serious visual disability. Ciprofloxacin (CIP), moxifloxacin (MOX), and levofloxacin (LFX) have been accepted as monotherapies by the US Food and Drug Administration for BK treatment. CIP is available commercially at 0.3% w/v concentration as an ophthalmic solution and as an ointment for ocular delivery. Because of solubility issues at physiological pH, CIP precipitation can occur at the corneal surface post instillation of the solution dosage form. Consequently, the ocular bioavailability of CIP is reduced. The ointment dosage form is associated with side effects such as blurred vision, itching, redness, eye discomfort, and eye dryness. This study aimed to design a CIP loaded nanoemulsion (NE; CIP-NE) to facilitate drug penetration into the corneal layers for improved therapeutic outcomes as well as to overcome the drawbacks of the current commercial ophthalmic formulations. CIP-NE formulations were prepared by hot homogenization and ultrasonication, using oleic acid (CIP-O-NE) and Labrafac® Lipophile WL 1349 (CIP-L-NE) as the oily phase, and Tween® 80 and Poloxamer 188 as surfactants. Optimized CIP-NE was further evaluated with respect to in vitro release, ex vivo transcorneal permeation, and moist heat sterilization process, using commercial CIP ophthalmic solution as a control. Optimized CIP-O-NE formulation showed a globule size, polydispersity index, and zeta potential of 121.6 ± 1.5 nm, 0.13 ± 0.01, and −35.1 ± 2.1 mV, respectively, with 100.1 ± 2.0% drug content and was spherical in shape. In vitro release and ex vivo transcorneal permeation studies exhibited sustained release and a 2.1-fold permeation enhancement, respectively, compared with commercial CIP ophthalmic solution. Autoclaved CIP-O-NE formulation was found to be stable for one month (last time-point tested) at refrigerated and room temperature. Therefore, CIP-NE formulation could serve as an effective delivery system for CIP and could improve treatment outcomes in BK.

An Analytic Investigation of the Drug Formulation-Based Recalls in the USA: See More Beyond the Literal.

High numbers of drug recalls persist despite the tremendous time and effort invested by pharmaceutical organizations and regulatory bodies such as the Food and Drug Administration (FDA) to ensure the quality of safe and effective medicines for the patient. It is imperative to better understand the underlying risk factors of drug formulation-based recalls to best protect the patient from poor quality drugs. Increased knowledge of underlying factors of formulation risk can also help inform the future design and development of drugs. In this study, we used a text mining technique with Python to parse the data and examine drug recalls from the aspect of administration route, dosage form, release mechanism, market type, pharmacologic class, and excipients. Observational analysis of the recalls revealed both high- and low-risk factors for the formulation-based recalls. Higher risk, or an increased probability of a formulation-based recall, was associated with factors such as extended release mechanism, capsule dosage form, oral route of administration, and an increased number of excipients, while lower risk of formulation-based recalls was associated with other factors including the new drug application market type, immediate release mechanism, and solution dosage form. In addition, the factors did not work independently, and we observed interactions among variables. For example, the release mechanism modified the effect of market type, administration route, and dosage form. This study will help inform the future design of quality drug products by pharmaceutical organizations and assist risk-based oversight by regulatory organizations, such as FDA, to ensure patient safety.

Stability Indicating HPLC Method Using Core Shell Stationary Phase for the Determination of Related Substances in Levocetirizine Dihydrochloride Oral Solution

Abstract: Rationale: Levocetirizine (LCZ) is a new generation antihistamine drug used for the allergic symptoms resulting from various diseases. The present research work focuses on the development of a simple and precise HPLC method for the effective separation and quantitative determination of LCZ and its impurities. Experimental: Eight potential related impurities of LCZ were separated and identified in the bulk drug as well as oral solution dosage form. The separation was achieved on a core shell stationary phase Kinetex bipheyl (250, 4.6×5 μm) column with mobile phase of sodium perchlorate in water and acetonitrile in a gradient elution. Results:The results were monitored and analytes were quantified at 230 nm. The method was validated as per ICH guidelines for specificity, linearity, precision, accuracy and robustness. The proposed method finds its application in the routine analysis of LCZ in bulk drug and various dosage forms. Key words: HPLC, Core shell, Related Substances, Levocetirizine dihydrochloride.

Route of administration and formulation dependent pharmacokinetics of 17-hydroxyprogesterone caproate in rats

1. Weekly intramuscular injections of (250 mg/week) of 17-hydroxyprogesterone caproate (17-OHPC) are the only treatment option for prevention of preterm birth in women with a prior history of preterm delivery.2. The objective of the current study was to evaluate the use of an alternate formulation and the feasibility of an alternate route of administration of this agent. 17-OHPC was administered to adult female SD rats, as marketed oily formulation intramuscularly, or as a solution IV, IM, or PO.3. Plasma concentrations of 17-OHPC were measured by LC-MS-MS and pharmacokinetic parameters were calculated by non-compartmental analysis, using WinNonLin (Certara, St. Louis, MO).4. After IV or IM administration as a solution, the mean half-life of 17-OHPC was around 11 h. The bioavailability was nearly 100% after IM administration, but was very low (<3%) after PO administration of a solution dosage form.5. Intramuscular injection of the oily formulation resulted in low levels of 17-OHPC that were sustained for a prolonged time period with a projected bioavailability close to 100%.6. The pharmacokinetics of 17-OHPC is dependent on the formulation and the route of administration.7. The low bioavailability after oral administration indicates that oral administration of 17-OHPC may not be feasible with simple formulations of this drug.

Development and Validation of RP-HPLC Method for the Simultaneous Determination of Trimethoprim, Sulfadimidine Sodium and Tylosin Tartrate in injectable solution formulation

Formation and Characterization of Sulfamethoxazole-Trimethoprim Cocrystal by Milling ProcessErizal Zaini, Yeyet C. Sumirtapura, Auzal Halim, Lili Fitriani, Sundani N. Soewandhi

Preparation and evaluation of ritodrine buccal tablets for rational therapeutic use

Ritodrine hydrochloride (RD-HCl) tablets containing alginate (AL) and lactose (LC) with or without microcrystalline cellulose (MC) as excipients were produced as a buccal dosage form. The RD-HCl (2 mg) tablets with AL/LC but no MC swelled and dissolved gradually in the in vitro dissolution test. The tablet showing the fastest dissolution and highest drug release rate, called Tablet A1, was selected as a tablet to show rapid and prolonged absorption. However, in the in vivo buccal absorption test using rats, it could not give a plasma concentration over the human minimal effective level (15 ng/mL). The modified tablet containing AL, LC, MC and RD-HCl (4 mg), named Tablet B/MC, showed better hardness and faster drug release. Tablet B/MC gave a plasma concentration over the human effective level within 15 min, and the plasma concentration was maintained at >15 ng/mL over 4 h. Moreover, the deconvolution analyses demonstrated that a prolonged high absorption rate could be achieved in vivo best with Tablet B/MC. Tablet B/MC improved the pharmacokinetic profile in comparison with Tablet A1 and the solution dosage form. The RD-HCl buccal tablets with AL, LC and MC as excipients are suggested to be possibly useful for the treatment of premature labor.

Determination of Thiomersal, Lidocaine and Phenylepherine in their Ternary Mixture

This work is concerned with the development and validation of two accurate, precise and specific spectrophotometric and chromatographic methods for analysis of Phenylepherine (PE), Lidocaine (LC) and Thiomersal (TM) in their ternary mixture and in Chromoderm® solution. The developed spectrophotometric method is the mean centering of ratio spectra (MCR) spectrophotometric method that depends on using the mean centered ratio spectra in two successive steps which eliminates the derivative steps and therefore the signal to noise ratio is enhanced. On the other hand, the developed chromatographic method isocratic RP-HPLC method that depends chromatographic separation on Zorbax C18 column using a mobile phase consisting phosphate buffer: acetonitrile: triethylamine (40:60:0.1, by volume pH=6 with orthophosphoric acid). The flow rate was 0.6 mL min-1 and the eluent was monitored at 245 nm. Factors affecting the developed methods were studied and optimized. Moreover, they have been validated as per ICH guidelines. The developed methods have been successfully applied for determination of PE, LC and TM in different laboratory mixtures and in solution dosage form. Also, Statistical analysis of the results of the two developed methods with each other using F and student’s t tests showed no significant difference

Validation of a Stability-Indicating Hydrophilic Interaction Liquid Chromatographic Method for the Quantitative Determination of Vitamin K3 (Menadione Sodium Bisulfite) in Injectable Solution Formulation

A simple, specific, accurate, and stability-indicating method was developed and validated for the quantitative determination of menadione sodium bisulfite in the injectable solution formulation. The method is based on zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) coupled with a photodiode array detector. The desired separation was achieved on the ZIC-HILIC column (250 mm × 4.6 mm, 5 μm) at 25°C temperature. The optimized mobile phase consisted of an isocratic solvent mixture of 200mM ammonium acetate (NH4AC) solution and acetonitrile (ACN) (20:80; v/v) pH-adjusted to 5.7 by glacial acetic acid. The mobile phase was fixed at 0.5 ml/min and the analytes were monitored at 261 nm using a photodiode array detector. The effects of the chromatographic conditions on the peak retention, peak USP tailing factor, and column efficiency were systematically optimized. Forced degradation experiments were carried out by exposing menadione sodium bisulfite standard and the injectable solution formulation to thermal, photolytic, oxidative, and acid-base hydrolytic stress conditions. The degradation products were well-resolved from the main peak and the excipients, thus proving that the method is a reliable, stability-indicating tool. The method was validated as per ICH and USP guidelines (USP34/NF29) and found to be adequate for the routine quantitative estimation of menadione sodium bisulfite in commercially available menadione sodium bisulfite injectable solution dosage forms.

Evaluating the taste masking effectiveness of various flavors in a stable formulated pediatric suspension and solution using the Astree™ electronic tongue

Pediatric formulation development requires an understanding of the physico-chemical stability and the taste of the pharmaceutical drug product. Two model active pharmaceutical ingredients (compound X and compound Y) were used to develop a powder for reconstitution to a suspension and a solution dosage form after dilution with purified water. X-ray powder diffraction was used to monitor the physical stability of compound X in the suspension and high pressure liquid chromatography was used to monitor the chemical stability of compound Y in the solution. The most stable suspension (formulation T) and solution (formulation Z) were used to assess the change in taste-perception by different flavors using the Astree™ electronic tongue. The suspension was determined to be stable for 43days and 21days respectively at 5°C and 25°C/60% RH. Compound Y solution was chemically stable for up to 30days at 25°C/60% RH. The taste of the suspension was improved by Lemon and Cherry flavors. The taste of the solution was made better by Vanilla, Cherry, and Strawberry flavors. The significance of these results is that the e-Tongue can be used in the early stages of formulation development to eliminate flavors that do little to improve the palatability of a formulation.

Estudo de estabilidade do fosfato dissódico de prednisolona em condições de estresse oxidativo e térmico, em formulação oral

Este trabalho consistiu em investigar o processo de degradação do fármaco Fosfato Sódico de Prednisolona (FSP) na forma farmacêutica de solução oral por meio de ensaios de degradação, avaliando-se os parâmetros de acordo com a Resolução nº. 899/2003 da ANVISA e o processo de degradação do fármaco. O método por cromatografia líquida de alta eficiência (CLAE), desenvolvido para o doseamento do fármaco, foi validado a fim de comprovar sua aplicabilidade como indicativo de estabilidade, assegurando a confiabilidade do mesmo. Após o método ser validado no estudo da degradação do fármaco, comprovou-se que em condições drásticas de estresse oxidativo (H2O2 30%) e temperatura a 60°C, a degradação do fármaco é dependente de sua concentração (cinética de primeira ordem). Os resultados apresentaram-se satisfatórios, demonstrando que este método é adequado para investigação da formação de produtos de degradação na forma farmacêutica solução oral.

Biodistribution Study Using Egg Protein ELISA Kit after Administration of FITC-labeled Ovalbumin Solution and Its Double Liposomes in the In Situ Loop Method, and Its Implication in Oral Immunization

Ovalbumin (OVA) is often used as a model antigen, and its biodistribution is important for the induction of immunization, especially oral immunization. In this study, an allergic substance-detecting kit, Egg Protein ELISA kit, was applied to the investigation of the biodistribution of fluorescein isothiocyanate-labeled ovalbumin (FITC-OVA). After FITC-OVA solution and its double liposomes were administered into the intestinal loop with one Peyer's patch, the biodistribution of FITC-OVA was examined with the Egg Protein ELISA kit. Each calibration was performed by fitting a quadratic curve to the observed ELISA response points. The ELISA response was almost the same between OVA and FITC-OVA. Similar ELISA response curves were obtained in Peyer's patch (PP) homogenate, spleen (SP) homogenate and plasma (PL). The concentration of FITC-OVA could be determined at 4 - 64 ng/ml for aqueous solution and SP homogenate and at 1 - 64 ng/ml for PP homogenate and PL. Thus, it was suggested that the ELISA kit should be useful for measurement of OVA biodistribution in an oral immunization study. After the administration of FITC-OVA solution and its double liposomes into the intestinal loop, the biodistribution of OVA-FITC in PP, SP and PL was investigated. The distributed amount was the greatest in PP. At the early time, the distributed amount in PP, SP and PL tended to be greater with FITC-OVA solution than the double liposomes. FITC-OVA was retained longer in PP with the double liposomes than FITC-OVA solution. The present results indicated that OVA could transfer well to PP and systemic circulation even with the solution dosage form in the loop method, probably because it was not exposed to harsh conditions such as a gastric fluid. Namely, it implied that the protection from gastric pH and enzyme by the double liposomes, which had been reported before, would be importantly associated with the promotion of immune induction. In addition, the double liposomes could retain OVA longer in PP, which might cause the enhancement of oral immunization.

Physicochemical Characterization of Berberine Chloride: A Perspective in the Development of a Solution Dosage Form for Oral Delivery

The objective of the present research was to evaluate the physicochemical characteristics of berberine chloride and to assess the complexation of drug with 2-hydroxypropyl-β-cyclodextrin (HPβCD), a first step towards solution dosage form development. The parameters such as log P value were determined experimentally and compared with predicted values. The pH-dependent aqueous solubility and stability were investigated following standard protocols at 25°C and 37°C. Drug solubility enhancement was attempted utilizing both surfactants and cyclodextrins (CDs), and the drug/CD complexation was studied employing various techniques such as differential scanning calorimetry, Fourier transform infrared, nuclear magnetic resonance, and scanning electron microscopy. The experimental log P value suggested that the compound is fairly hydrophilic. Berberine chloride was found to be very stable up to 6 months at all pH and temperature conditions tested. Aqueous solubility of the drug was temperature dependent and exhibited highest solubility of 4.05 ± 0.09 mM in phosphate buffer (pH 7.0) at 25°C, demonstrating the effect of buffer salts on drug solubility. Decreased drug solubility was observed with increasing concentrations of ionic surfactants such as sodium lauryl sulfate and cetyl trimethyl ammonium bromide. Phase solubility studies demonstrated the formation of berberine chloride-HPβCD inclusion complex with 1:1 stoichiometry, and the aqueous solubility of the drug improved almost 4.5-fold in the presence of 20% HPβCD. The complexation efficiency values indicated that the drug has at least threefold greater affinity for hydroxypropyl-β-CD compared to randomly methylated-β-CD. The characterization techniques confirmed inclusion complex formation between berberine chloride and HPβCD and demonstrated the feasibility of developing an oral solution dosage form of the drug.

Estudo de estabilidade do fosfato dissódico de prednisolona em condições de estresse oxidativo e térmico, em formulação oral

Este trabalho consistiu em investigar o processo de degradação do fármaco Fosfato Sódico de Prednisolona (FSP) na forma farmacêutica de solução oral por meio de ensaios de degradação, avaliando-se os parâmetros de acordo com a Resolução nº. 899/2003 da ANVISA e o processo de degradação do fármaco. O método por cromatografia líquida de alta eficiência (CLAE), desenvolvido para o doseamento do fármaco, foi validado a fim de comprovar sua aplicabilidade como indicativo de estabilidade, assegurando a confiabilidade do mesmo. Após o método ser validado no estudo da degradação do fármaco, comprovou-se que em condições drásticas de estresse oxidativo (H2O2 30%) e temperatura a 60°C, a degradação do fármaco é dependente de sua concentração (cinética de primeira ordem). Os resultados apresentaram-se satisfatórios, demonstrando que este método é adequado para investigação da formação de produtos de degradação na forma farmacêutica solução oral.

A tumor vasculature targeted liposome delivery system for combretastatin A4: Design, characterization, and in vitro evaluation

The objective of this study was to develop an efficient tumor vasculature targeted liposome delivery system for combretastatin A4, a novel antivascular agent. Liposomes composed of hydrogenated soybean phosphatidylcholine (HSPC), cholesterol, distearoyl phosphoethanolamine-polyethylene-glycol-2000 conjugate (DSPE-PEG), and DSPE-PEG-maleimide were prepared by the lipid film hydration and extrusion process. Cyclic RGD (Arg-Gly-Asp) peptides with affinity for alphavbeta3-integrins expressed on tumor vascular endothelial cells were coupled to the distal end of PEG on the liposomes sterically stabilized with PEG (long circulating liposomes, LCL). The liposome delivery system was characterized in terms of size, lamellarity, ligand density, drug loading, and leakage properties. Targeting nature of the delivery system was evaluated in vitro using cultured human umbilical vein endothelial cells (HUVEC). Electron microscopic observations of the formulations revealed presence of small unilamellar liposomes of approximately 120 nm in diameter. High performance liquid chromatography determination of ligand coupling to the liposome surface indicated that more than 99% of the RGD peptides were reacted with maleimide groups on the liposome surface. Up to 3 mg/mL of stable liposomal combretastatin A4 loading was achieved with approximately 80% of this being entrapped within the liposomes. In the in vitro cell culture studies, targeted liposomes showed significantly higher binding to their target cells than nontargeted liposomes, presumably through specific interaction of the RGD with its receptors on the cell surface. It was concluded that the targeting properties of the prepared delivery system would potentially improve the therapeutic benefits of combretastatin A4 compared with nontargeted liposomes or solution dosage forms.