Rapid screening of antioxidants in pharmaceutical formulation development using cyclic voltammetry--potential and limitations.

Cyclic voltammetry (CV) is a unique technique for the electrochemical characterization of compounds by providing their oxidation/reduction potentials. This technique is widely used in evaluating antioxidants in the oil, food, diagnostic and agricultural industries; however, CV is rarely used in the development of pharmaceutical formulations. This review briefly describes the basic principles of CV and its application in other industries along with the potential and limitations of CV in the rapid evaluation of antioxidants in pharmaceutical formulations.

Rapid determination of trace amounts of minoxidil in hamster skin follicles with various formulations using narrow-bore LC/EC.

A sensitive liquid chromatographic method with electrochemistry (LC/EC) was developed for the determination of trace of minoxidil in hamster skin follicles after topical administration of the ear using various formulations. The minoxidil in the sebaceous glands of the hamster ear was isolated from the skin and the follicles in different skin layers were treated with aqueous trichloroacetic acid followed by acetonitrile. The supernatant was directly injected into the LC/EC system and minoxidil was detected by oxidation at +800 mV versus Ag/AgCl using a glassy carbon electrode.

Enhanced oral bioavailability of a poorly water soluble drug PNU-91325 by supersaturatable formulations.

Supersaturatable cosolvent (S-cosolvent) and supersaturatable self-emulsifying drug delivery systems (S-SEDDS) are designed to incorporate water soluble cellulosic polymers such as hydroxypropyl methylcellulose (HPMC), which may inhibit or retard drug precipitation in vivo. A poorly soluble drug, PNU-91325, was used as a model drug in this study to illustrate this formulation approach. The comparative in vitro studies indicated that the presence of a small amount HPMC in the formulation was critical to achieve a stabilized supersaturated state of PNU-91325 upon mixing with water.

Development of a supersaturable SEDDS (S-SEDDS) formulation of paclitaxel with improved oral bioavailability.

A new, supersaturable self-emulsifying drug delivery system (S-SEDDS) of paclitaxel was developed employing hydroxypropyl methylcellulose (HPMC) as a precipitation inhibitor with a conventional SEDDS formulation. In vitro dilution of the S-SEDDS formulation results in formation of a microemulsion, followed by slow crystallization of paclitaxel on standing. This result indicates that the system is supersaturated with respect to crystalline paclitaxel, and the supersaturated state is prolonged by HPMC in the formulation.

Liquid chromatographic determination of residual hydrogen peroxide in pharmaceutical excipients using platinum and wired enzyme electrodes.

Hydrogen peroxide (H(2)O(2)) is a chemically reactive reagent that can oxidize and degrade many pharmaceutical compounds under normal conditions. Unfortunately, H(2)O(2) is often introduced into pharmaceutical excipients during manufacturing and it may significantly affect the chemical stability of drugs in formulations. Thus, a sensitive analytical method for determination of residual H(2)O(2) in excipients is of importance in formulation development and product quality control.