Studies on the mechanism of spironolactone protection against indomethacin toxicity

Nanoshells prepared by atomic layer deposition - Long acting depots of indomethacin

There is a trend in pharmaceutical research and development to develop depot formulations with dosing once weekly, once monthly, or even less frequently. A novel approach to achieve long acting injectable suspensions is to produce dense inorganic nanoshells with atomic layer deposition (ALD) on active pharmaceutical ingredients. Such particles can be suspended in an aqueous vehicle and administered subcutaneously. The purpose of this work was to study the release of a model drug, indomethacin, coated with aluminium oxide nanoshells. Indomethacin was ball-milled to a median particle size of 6 µm. The nanoshells were produced with a proprietary ALD process that is trademarked as PharmaShell® by Nanexa AB. The drug load was determined with HPLC-UV to 82 wt%. The test materials were administered subcutaneously in rats (1, 10, and 100 mg/kg) from which blood samples were collected during 12 weeks. Plasma was generated and analyzed with regards to indomethacin using UPLC-MS/MS. The release rate was dramatically slower for the nanoshell coated indomethacin compared with uncoated indomethacin. Drug was released in vivo during more than 12 weeks for the 10 and 100 mg/kg doses, and during 10 weeks for the 1 mg/kg dose, while uncoated indomethacin was eliminated with a half-life of 15 h, as calculated from the release data by fitting a one phase decay function. The exposure levels were similar as earlier reported for therapeutic indomethacin doses, but significantly sustained in the present study using coated drug particles in rats. In conclusion, this is the first long-term in vivo evaluation of nanoshell depot formulations. The stable plasma concentrations for more than 12 weeks demonstrate that nanoshells can enable long-term depot injections with high drug load.

Amphiphilic poly-N-vinylpyrrolidone nanoparticles as carriers for non-steroidal, anti-inflammatory drugs: In vitro cytotoxicity and in vivo acute toxicity study

Polymeric nanoparticles were prepared from self-assembled amphiphilic N-vinylpyrrolidone polymers in aqueous media and evaluated as novel carriers of indomethacin, a non-steroidal, anti-inflammatory drug. It was determined that these nanoparticles could be created in spherical morphologies with sizes less than 100nm, narrow size distributions and high indomethacin contents(up to 35%) combined with high drug loading efficiencies(up to 95%). In cytotoxicity tests using the human embryonic stem cell derived fibroblasts (EBF-H9) and hepatocellular carcinoma cells (HepG2), the indomethacin-loaded polymeric nanoparticles showed higher cell viability compared to that of free indomethacin at the same concentration. The median LD₅₀ values, determined by the Litchfield-Wilcoxon method, were 55-70mg/kg body weight depending on the polymer molecular design in both mice and rats. Based on the acquired results, these novel amphiphilic poly-N-vinylpyrrolidone nanoparticles can be considered as potential carriers for new, highly efficient, injectable drug delivery systems for hydrophobic drugs such as indomethacin.

Bartter's syndrome without hyperplasia of the juxtaglomerular apparatus, treated with indomethacin

The present report describes a case of potassium-wasting nephropathy with the physiological and endocrinological findings that are typical for Bartter's syndrome (BS). However, the renal juxtaglomerular apparatus showed no hyperplasia at two renal biopsies two years apart. The short-term (9 days) effect of indomethacin in combination with spironolactone was a suppression of hyperreninemia and hyperaldosteronism and an increase in vascular sensitivity to angiotensin II associated with potassium and sodium retention. Subsequently, on indomethacin alone, potassium balance was obtained on a lower level with persistent hypokalemia and persistent renal potassium leakage. Hypokalemia persisted during long-term (9 months) treatment with indomethacin despite normalization of the activity of the renin-aldosterone system. The results indicate that indomethacin as long-term treatment may be ineffective in maintaining a normal potassium balance in BS.

Nitric oxide involvement in lipid emulsion-induced vascular pain in anesthetized rats

We examined the vascular pain induced by arterial infusion of 20% lipid emulsion by using a flexor reflex model in anesthetized rats. Arterial infusion of 20% lipid emulsion at doses of 0.6 to 2 ml/2 min induced flexor reflexes that were late in onset, persistent, and intense compared with those induced by 2.7% amino acid and 7.5% glucose solution, 5% sodium chloride solution, 1% propofol, and capsaicin. The flexor reflex induced by 20% lipid emulsion was significantly inhibited by preinjected procaine hydrochloride (4 mg/rat, i.a.) but not by the critical dose of indomethacin (10 mg/kg, i.p.). These results suggest that the flexor reflex might reflect a 20% lipid emulsion-induced vascular pain response and that the site of action of noxious agents involved in this event might be a vascular bed, but the production of prostanoids through cyclooxygenase might not be involved in the action mechanisms. The 20% lipid emulsion-induced vascular pain was significantly inhibited by preinjection of 10 mg/kg N(G)-nitro-l-arginine methyl ester hydrochloride (l-NAME), a nitric oxide (NO) synthase inhibitor, and the inhibition by l-NAME was recovered by the addition of sodium nitroprusside (30 microg/kg/min), which is an endothelium-independent NO donor to 20% lipid emulsion. These results indicate that increased NO production is responsible for 20% lipid emulsion-induced vascular pain. In summary, the arterial infusion of 20% lipid emulsion induced a delayed, persistent and intense flexor reflex, presumably indicating vascular pain in rats that might be induced by NO production through the activation of NO synthase.

Toxic characteristics of methoxy poly(ethylene glycol)/poly(epsilon-caprolactone) nanospheres; in vitro and in vivo studies in the normal mice

Amphiphilic diblock polymeric nanospheres composed of methoxy poly(ethylene glycol) (MePEG) and poly(epsilon-caprolactone)(PCL) was prepared for application as a novel drug carrier. We could obtain the MePEG/PCL nanospheres that exhibited an average diameter of less than 200 nm with narrow size distribution and a relatively high drug-loading efficiency of about 41.98% and 20.8% for indomethacin and paclitaxel, respectively. To estimate the toxicity of nanospheres, we investigated cytotoxicity using the normal human fibroblast, the median lethal dose (LD(50)) and various organ toxicities using male ICR mice. The indomethacin-loaded nanosphere showed higher cell viability than indomethacin in the cytotoxicity test using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The LD(50) of MePEG/PCL nanospheres determined by Litchfield-Wilcoxon method was 1.47 g/kg. After the mice were intraperitoneally injected with MePEG/PCL nanospheres as a half-dose level of LD(50) for 7 days, no significant histopathologic changes were observed in MePEG/PCL nanospheres-treated mice compared with normal mice in the light and electron microscopic observations of various organs such as heart, lung, liver and kidney. It was suggested that MePEG/PCL nanospheres might be useful candidate as a novel injectable drug carrier for hydrophobic drugs such as indomethacin and paclitaxel.

Decreased hepatic microsomal cytochrome P450 due to indomethacin: protective roles of 16,16-dimethylprostaglandin F2 alpha and inducing agents

Indomethacin administration to rats caused a dose-dependent decrease in hepatic microsomal cytochrome P450, aminopyrine N-demethylase, ethoxyresorufin O-de-ethylase and benzyloxyresorufin O-debenzylase, accompanied by selective alterations in microsomal sodium dodecylsulphate polyacrylamide gel electrophoretograms. High doses (greater than or equal to 8.5 mg/kg) caused the disappearance of certain of the SDS-PAGE proteins tentatively identified as being different forms of cyt. P450, together with either increases, decreases or no change in some of the non-cyt. P450 proteins in the electrophoretogram. Concomitant administration of 16,16-dimethylprostaglandin F2 alpha gave dose-dependent protection against the deleterious effects of indomethacin on the enzymic and electrophoretic parameters of cyt. P450, but did not prevent the changes due to indomethacin in the non-cyt. P450 proteins on the electrophoretogram. In contrast, prior phenobarbitone or 3-methylcholanthrene induction prevented the effects of indomethacin on both cyt. P450 and the other microsomal proteins. Concomitant administration of SKF-525A exacerbated the effects of indomethacin on cyt. P450 and the other proteins. Indomethacin coadministration with 3-methylcholanthrene resulted in the major 3MC-induced putative cyt. P450 apoprotein having a lower mol. wt than usual. Conversely, indomethacin did not prevent the induction by SKF-525A of a different putative cyt. P450 apoprotein, despite causing decreases in cyt. P450 as determined spectrophotometrically and enzymologically. The results indicate that indomethacin rather than one of its metabolites is responsible for the decrease in cyt. P450 and that the mechanisms of protection by prostaglandin and inducing agents are, respectively, different.

Investigation of the interaction between Probon and indomethacin in rats

The toxic side-effects and anti-inflammatory activity of combination treatment of Sprague-Dawley rats with indomethacin and Probon, a new type of analgesic, were investigated. Following four weeks of treatment with a combination of these two drugs, the characteristic gastrointestinal side-effect of indomethacin was markedly reduced. Mortality resulting from administration of the drug combination was significantly lower than that resulting from indomethacin treatment alone. The reduced toxicity of indomethacin in combination with Probon is probably due to a change in metabolism produced by the hepatic microsomal enzyme inducer, Probon. The anti-inflammatory effect was also investigated using a contact thermographic method following one, three or seven days pretreatment. The advantage of this combination is that, using a higher dose of indomethacin in combination with the minor analgesic, we could achieve a more reliable anti-inflammatory effect together with a pain-killing action.

Influence of spironolactone on cadmium-induced changes in hepatic and renal gluconeogenic enzymes in rats

Serum glucose, serum protein, serum glutamic oxalacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), and hepatic and renal gluconeogenic enzymes [pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-diphosphatase (F-1,6-DPase), and glucose-6-phosphatase (G-6-Pase)] were determined in rats treated daily with cadmium alone (0.25 mg/kg X d, injected ip and in rats pretreated with spironolactone (50 mg/kg x d and 100 mg/kg X d, injected sc) prior to cadmium administration. Rats receiving no treatment, propylene glycol, or spironolactone (100 mg/kg X d, injected sc) were used as controls. The daily treatments were continued for an extended period of 90 d, and the rats were sacrificed at 30-, 60-, and 90-d intervals during the continuous daily treatment schedule. Cadmium treatment significantly increased the amount of serum protein, glucose, serum enzymes, and all the four key gluconeogenic enzymes as compared to controls. Pretreatment of rats with spironolactone 6 h prior to cadmium injection daily antagonized the cadmium effect of the above parameters. It appears from these results that spironolactone reduces the effects of cadmium on the key gluconeogenic enzymes in rat kidney and liver.

Relationship between prostaglandins and cyclic-AMP in the process of implantation in rats

The effect of alloxan, a known inhibitor of adenylate cyclase, on the levels of prostaglandins E and F was investigated in pregnant rats. Animals were treated intraluminally with alloxan in normal saline or alloxan plus cyclic-AMP in normal saline or normal saline alone on day 4 of pregnancy. The uteri were collected on days 5 and 6 of pregnancy and the prostaglandins E and F were extracted and measured by a radioimmunoassay technique. In the alloxan treated rats, a significant reduction in PGE and PGF levels was found on days 5 and 6 of pregnancy as compared to untreated control group, whereas in the alloxan plus cyclic-AMP treated group the levels of PGE and PGF were comparable to those of the untreated control group. These findings suggest a possible relationship between prostaglandins and cyclic-AMP in the process of implantation in rats.

Effects of antihypertensive drugs on hepatic heme biosynthesis, and evaluation of ferrochelatase inhibitors to simplify testing of drugs for heme pathway induction

Effects of a series of antihypertensive drugs on the activity of delta-aminolevulinate synthase and on the formation of porphyrins and cytochrome P-450 were examined in the 18-day-old chick embryo liver in ovo. Hydralazine, pargyline, phenoxybenzamine, clonidine, and spironolactone were found to induce delta-aminolevulinate synthase in this system. These drugs therefore have the potential to precipitate clinical expression in human hereditary hepatic porphyrias and should be avoided or used with caution in patients with these disorders. Differential effects of these and other drugs were observed in the avian liver, in that delta-aminolevulinate synthase was more commonly induced than were porphyrins and cytochrome P-450; the synthase was usually highest 6-12 h after injection, whereas porphyrins and cytochrome P-450 were highest at 24 h. Furthermore marked porphyrin accumulation was not seen with many drugs that induce delta-aminolevulinate synthase and cytochrome P-450 but was more characteristic of compounds that reduced the metabolism of protoporphyrin to heme, such as 1,4-dihydro-3,5-dicarbethoxycollidine (DDC) and high doese of hydralazine. A sensitive and convenient method to test for capacity to induce heme biosynthesis was adapted for use in the chick embryo liver. This employed a relatively small "priming" dose (0.25 mg) of DDC given with a drug being tested and a fluorometric assay of porphyrins in a liver homogenate obtained at 24 h. This simple method should facilitate screening for those drugs which induce the synthesis of delta-aminolevulinate synthase and/or cytochrome P-450 and are potentially dangerous to patients with hereditary hepatic porphyria.