In Vitro Approach to investigating the phototoxicity of the diuretic drug triamterene.

Our approach to assessing the photobiological risk of drugs combines photochemical and physicochemical studies with in vitro testing on human serum, human erythrocytes, lymphocytes and neutrophils. We have used this approach to investigate the photobiological risk of the diuretic drug triamterene, which has shown phototoxic effects in vivo. Photodecomposition studies of triamterene in methanol, phosphate buffered saline (PBS) solution and human serum, in the presence of oxygen, was followed by UV spectrophotometry and HPLC analysis using a sensitive HPLC method. Its photodegradation was observed only under irradiation with UV-B (290-320nm) light to produce the photoproduct 2. No photodecomposition was detected under UV-A (320-400nm) irradiation, yet singlet oxygen was generated. Triamterene shows a photohaemolytic effect and photoinduced lipid peroxidation. In the presence of oxygen, triamterene was able to induce photohaemolysis of human erythrocytes. The same process was observed under an inert atmosphere, although at a significantly lower rate. Studies on peripheral blood mononuclear and polymorphonuclear cells (lymphocytes and neutrophils) demonstrated phototoxicity on these cell lines.

Photodegradation and phototoxicity studies of furosemide. Involvement of singlet oxygen in the photoinduced hemolysis and lipid peroxidation.

The phototoxic diuretic drug furosemide (1), a 5-(aminosulfonyl)-4-chloro-2-[(2-furanylmethyl)-amino] benzoic acid is photolabile under aerobic and anaerobic conditions. Irradiation of a methanol solution of 1 under oxygen produces photoproducts 2, 3, 4 and singlet oxygen, while under argon the photoproducts 2 and 4 were isolated. A peroxidic unstable photoproduct was detected during the photolysis under oxygen atmosphere. The formation of singlet oxygen by photolysis of 1 was evidenced by trapping with 2,5-dimethylfuran (GC-mass), furfuryl alcohol and 1,3-cyclohexadiene-1,4-diethanoate (HPLC) as 1O2 scavengers and by the histidine test. Furosemide was screened in vitro at different concentrations for UV-Vis-induced phototoxic effects in a photohemolysis test, in the presence and absence of different radical scavengers, singlet oxygen and hydroxyl radical quenchers. However, furosemide photosensitized the peroxidation of linoleic acid, as monitored by the UV-detection of dienic hydroperoxides and it also photosensitized the oxidation of histidine. The photodegradation was catalyzed in the presence of human serum albumin. Studies on peripheral blood mononuclear and polymorphonuclear cells (lymphocytes and neutrophils) demonstrated no phototoxicity on these cell lines.

Long-term histopathologic evaluation of inferior vena cava after modified Greenfield filter implantation. Experimental study in sheep.

AIM: The authors assess a modified Greenfield filter (GF) for the long-term patency, filter tilting and histopathologic alterations of the inferior vena cava (IVC). METHODS: Adult sheep (n=7) underwent modified GF placement in the IVC. Cavograms were obtained every 3 months and pulmonary angiography at 12 months. Histopathologic and scanning electron microscopy (SEM) analyses were performed on the IVC explanted at 12 months. RESULTS: Cavograms showed that all IVC were patent at the end of the study. Filter tilting occurred in 2/7 animals and extrusion of struts was not observed. Macroscopic examination at explantation showed minimal venous wall thickening. Microscopic examination showed minimal IVC fibrosis and intimal hyperplasia. SEM showed endothelium on the IVC surface at the filter implantation site and a presumed endothelial layer covering partially or totally the struts. The interface filter-IVC was covered by deposits of leucocytes and platelets. No signs of pulmonary embolism were found in all pulmonary angiograms of both groups. CONCLUSION: The modified filter presented good biocompatibility, stability and absence of thrombogenicity at 12 months. It presented low tendency to tilting and extrusion of struts. The long-term histopathologic alterations in vena caval wall were minimal and the appearance of the studied filters in the IVC was similar to stents placed in the arterial system.

Photosensitizing activity of thiocolchicoside: photochemical and in vitro phototoxicity studies.

The phototoxic drug thiocolchicoside (2-dimethoxy-2-glucosidoxythiocolchicine, 1), is photolabile under irradiation with UV-A light from TL 100 W-P Philips bulbs (at lambda max 355 nm) light and also with a N2 laser (at 337 nm) in aerobic and anaerobic conditions. Irradiation of a methanol solution of 1 produces two photoproducts without a glucoside group. One of these lost the methylthio-group, while the other is oxidized (only under aerobic conditions) to sulfoxide. The formation of singlet oxygen by photolysis of 1 was evidenced by trapping with 2,5-dimethylfuran (GC-MS), furfuryl alcohol, 1,3-cyclohexadiene-1,4-diethanoate (HPLC) and by the histidine test as 1O2 scavengers. Thiocolchicoside has been shown to photosensitize the reduction of nitro blue tetrazolium by direct electron transfer mechanism, when irradiated under the same conditions as for photolysis. Oxygen may also be involved in this electron transfer reaction to form the superoxide anion radical. Thiocolchicoside was screened in vitro in different concentrations for UV-Vis-induced phototoxic effects in a photohemolysis test, in the presence and absence of different radical scavengers, singlet oxygen and superoxide radical quenchers. In addition, 1 photosensitized the peroxidation of linoleic acid, monitored by the UV-detection of dienic hydroperoxides. Studies on peripheral blood mononuclear cells (lymphocytes) demonstrated phototoxic effects on them. Protection by GSH, DABCO, sodium azide and SOD are indicative of both Type I and II photosensitization pathways mediated by free radicals and singlet molecular oxygen.