Paclitaxel (PTX) is a very effective antineoplastic agent used to treat a variety of tumors. It was discovered in the 1960s in a screening study by the National Cancer Institute designed to develop new natural substances with anticancer activity. PTX brought much hope to people with cancer, but its poor solubility in water and insufficient supply have slowed clinical studies of the drug. 1)After much investigation, an appropriate PTX formulation containing Cremophor EL (ethoxylated castor oil) and dehydrated ethanol (1 : 1 v/v) and suitable for intravenous infusion was found. The Bristol-Myers Squibb Company owned the first patent on a PTX formulation that was introduced to the market in 1993 under the name Taxol. At present, as the patent has expired, many generic products are on the market, all containing Cremophor EL. This solubilizing agent ensures sufficient drug solubility and stability but evokes many severe side effects.2,3) Cremophor EL is responsible for acute hypersensitivity reactions that affect about 30% of patients. It also contributes to peripheral neuropathy and leaches the plasticizers from polyvinyl chloride (PVC) bags and infusion sets. As a result, PTX solutions must be prepared and administered in non-PVC infusion systems with in-line filtration, and pre-medication must be given to patients. These issues have provoked considerable interest in the development of taxanes with improved aqueous solubility and in formulations devoid of Cremophor EL.Increased solubility of the drug, which is necessary for intravenous delivery, can be achieved by, for example, using co-solvents or preparing an emulsion, 1,4) by modification of the PTX molecule into prodrugs 5,6) or analogs, 7,8) and by preparing liposomes 4) or micelles. 9) However, none of these formulations has been introduced to clinical practice yet, due to the lack of sufficient biocompatibility to meet the requirements of intravenous preparations. However, in 2005 the FDA (Food and Drug Administration) approved Abraxane for injection (Abraxis BioScience), the first alternative to the Cremophor-containing preparation. It is a nanosuspension of PTX conjugated with human albumin. 10) Despite its better clinical profile, Abraxane is generally not replacing Taxol in oncological practice, mostly due to its high cost. Hence, further research into alternative formulations suitable for parenteral infusion is justified.The aim of our study was to develop a new PTX formulation using excipients that are already in use for parenteral administration. Since PTX must be given to the patients as an infusion, the choice of suitable carriers is very limited. Unfortunately, neither submicron, lecithin-based emulsions nor liposomes ensure appropriate PTX solubility and stability. For example, the solubility of PTX in soybean oil, which is used in parenteral emulsions, is about 180 mg/100 g, and this allows preparation of an emulsion with PTX at a concentration of only 18 mg/100 ml, if the oil content in the emulsion is 10%. PTX is soluble in some types of emulsi...

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Microscopy belongs to the group of tests, used in pharmaceutical technology, that despite the lapse of time and the development of new analytical methods, still remain irreplaceable for the characterization of dispersed drug dosage forms (e.g., suspensions and emulsions). To obtain complete description of a specific drug formulation, such as parenteral colloidal products, a combination of different microscopic techniques is sometimes required. Electron microscopy methods are the most useful ones; however, even such basic methods as optical microscopy may be helpful for determination of some properties of a sample. The publication explicates the most popular microscopical techniques used nowadays for characterization of the morphology of nanoparticles suspended in pharmaceutical formulations; ad vantages and disadvantages of these methods are also discussed. Parenteral submicron formulations containing lecithin or a particular phospholipid were chosen as examples.

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