Transdermal delivery of cyclosporin-A using electroporation.

Topical delivery of cyclosporin A (CSA) is desirable for treating psoriasis, but it is hindered by the barrier property of stratum corneum, and the physicochemical properties of CSA. Attempts to deliver CSA from a solution prepared in 40% ethanol (EtOH) is phosphate buffered saline (PBS) using iontophoresis did not result in any significant increase in drug delivery, compared to passive. However, the use of electroporation pulses as a physical penetration enhancer enabled delivery of a significant amount of CSA. Single pulse electroporation study indicated that the amount of EtOH delivered across the skin increased as the applied electrode voltage (Uelectrode) was increased. However, it did not translate into a proportional increase in the delivery of CSA and only a three to four times increase, compared to passive delivery, was seen with the single purse electroporation. The drug contact duration had a varying effect in the efficiency of transdermal delivery of CSA. Four hour contact duration was chosen for the multiple pulse study. Use of multiple pulses (25 pulses, 10 ms each) at Uelectrode 200 V resulted in a sixty-fold increase, compared to passive, in the delivery of CSA to the skin. Transdermally delivered CSA was mostly bound to the skin and only a small amount was seen to cross the full skin into the receiver compartment. In a study of solvent transport, the flux of water was up to three times larger than that of EtOH after electroporation.

Evaluation of cytotoxicity and absorption enhancing effects of melittin - a novel absorption enhancer.

Melittin is the major active ingredient in bee venom and has been widely studied for its membrane-fusion property. We have explored the possibility of determining a concentration range of melittin where it is relatively safe to be used as an adsorption enhancer. Melittin's potential use as an adsorption enhancer for mannitol was determined using Caco-2 cells as the model epithelial membrane. The results indicated that at concentrations below 2.4 (M melittin is safe. Using a melittin concentration of 1.5 (M there was 3.5 times increased transepithelial transport of mannitol across Caco-2 cell monolayers.

Transdermal drug delivery using electroporation. I. Factors influencing in vitro delivery of terazosin hydrochloride in hairless rats.

The use of electroporation pulses as a physical means of enhancing the permeability of skin to deliver drugs is in the early stages of development. In this article, a systematic study examining the parameters influencing electroporative transdermal delivery of terazosin hydrochloride to hairless rat skin are reported. It was found that voltage, pulse length (tau), and number of pulses were the three most important parameters, in that order. For creating a significant enhancement in drug delivery to the skin, without causing any apparent change in its external appearance, it was necessary to deliver five or more exponentially decaying electroporation pulses, at 88 +/- 2.5 V (voltage across the skin), with a decay time constant of 20 ms. Electrodes with larger area could attain the same voltages across the skin with a much lower applied voltage and possessed other advantages with regard to performance of the drug delivery system.

Transdermal drug delivery using electroporation. II. Factors influencing skin reversibility in electroporative delivery of terazosin hydrochloride in hairless rats.

A previous study indicated that the parameters governing the performance of electroporative delivery to the skin, are voltage, pulse length, number of pulses and electrode area.1 This article describes a study in which the reversibility of the electroporation technique is evaluated with in vitro methods. The skin's reversal from an enhanced permeation mode as a result of electroporation to the base level was used as an index to understand the mechanism of drug delivery and also as a preliminary indicator of safety. Maximum delivery of the model drug, terazosin hydrochloride, occurred during the pulsing. Electroporative delivery with a wire electrode (small-area electrode, 0.56 cm(2)) using 20 pulses at U(skin,0) 88 V, and pulse length 20 ms, did not cause any damage to the skin. Increasing the pulse length to 60 ms, while keeping the rest of the parameters fixed, caused a visible change in the external appearance of the skin. However, with the use of a spiral electrode (large-area electrode, 2.74 cm(2)) at 60-ms pulse length, there was minimal damage to the skin. This may be attributed to the more uniform flow of current over the whole skin area. The large-area electrode required a smaller electrode voltage, U(electrode,0) for any given U(skin,0) and also delivered nearly double the instantaneous power density compared with the small-area electrode. These findings indicate that using shorter pulses and large-area electrodes is a safer technique than large pulses and small-area electrodes when electroporation is used to enhance skin's permeability for drug delivery.

Solid-phase extraction technique for the analysis of biological samples.

This article reviews the literature on solid-phase extraction published in the last 10 years. Emphasis has been placed on dealing with samples of biological origin. The sections consist of introduction, history and development, types of columns, selection of a suitable column, types of samples, advantages and applications.

Alginate-pectin-poly-L-lysine particulate as a potential controlled release formulation.

Drug delivery particulates were prepared using alginate, polylysine and pectin. Theophylline, chlorothiazide and indomethacin were used as the model drugs for in-vitro assessments, and mannitol was the model for assessing paracellular drug absorption across Caco-2 cell monolayers. Alginate and pectin served as the core polymers and polylysine helped to strengthen the particulates. Use of pectin specially helped in forming a more robust particulate that was more resistant in acidic pH and modulated the release profiles of the encapsulated model drugs in the alkaline pH. Alginate and pectin were also found to enhance the paracellular absorption of mannitol across Caco-2 cell monolayers by about three times. The release rate could be described as a first-order or square-root time process depending on the drug load. Use of alginate-polylysine-pectin particulates is expected to combine the advantages of bioadhesion, absorption enhancement, and sustained release. This particulate system may have potential use as a carrier for drugs that are poorly absorbed after oral administration.

Comparative bioavailability of clofazimine coevaporate in the pig.

The systemic availability of a solid dispersion (coevaporate) of clofazimine (CLF) in poly(vinyl methyl ether maleic anhydride) copolymer (PVM/MA) was tested in the pig. Single 100 mg oral doses of the coevaporate and the commercial product, Lamprene (Ciba-Geigy) were administered on separate occasions (separated by a two-week washout period) to four pigs (two males, two females) in a random cross-over study. Multiple plasma samples, obtained from an indwelling jugular-vein cannula, following drug administration, were analysed by an HPLC method for CLF. Pharmacokinetic analyses of the plasma CLF concentration-time data were performed. A paired t-test indicated significant differences (p < 0.05) between the coevaporate and Lamprene in the Cpmax, tmax, and AUC. The calculated relative systemic bioavailability (Frel) of CLF from the coevaporate, relative to that from Lamprene, was three. It is concluded that formulation of CLF, as a solid dispersion, may provide enhanced aqueous dissolution and systemic absorption and may also provide high therapeutic blood levels. These could lead to reduction in the current therapeutic doses and, consequently, minimization of drug-related side effects.

A rapid and sensitive high performance liquid chromatographic analysis of clofazimine in plasma.

The high performance liquid chromatographic (HPLC) method of Gidoh, et al. has been modified substantially to provide a simple, rapid, and relatively inexpensive procedure for measuring clofazimine in plasma. The modification involves the use of commonly available laboratory reagents instead of custom-made ones. It also employs a solid phase system for efficient extraction instead of the conventional, less efficient and more labor intensive, liquid-liquid extraction. The inclusion of an internal standard (salicylic acid) improves the precision and reproducibility. It is demonstrated that the method can be used to monitor in vivo clofazimine levels as may be required in formal pharmacokinetic studies or therapeutic drug monitoring.