Horseradish peroxidase-catalyzed oxidation of acetaminophen to intermediates that form polymers or conjugate with glutathione

Horseradish peroxidase catalyzed the polymerization of acetaminophen. Addition of reduced glutathione (GSH) to reaction mixtures resulted in decreased polymerization and formation of minor amounts of GSH-acetaminophen conjugates. The conjugates were identified as 3-(glutathion-S-yl)acetaminophen and 3-(glutathion-S-yl)diacetaminophen. Horseradish peroxidase also catalyzed polymerization of synthetic 3-(glutathion-S-yl)acetaminophen to a dimer conjugate. In contrast to acetaminophen, 3-(glutathion-S-yl)acetaminophen oxidation was slowly catalyzed by horseradish peroxidase. However, in reaction mixtures containing equimolar concentrations of acetaminophen and synthetic 3-(glutathion-S-yl)acetaminophen, the formation of 3-(glutathion-S-yl)diacetaminophen and 3-(diglutathion-S-yl)diacetaminophen was rapid and accounted for approximately 95% of the products, whereas acetaminophen polymers accounted for only 5% of the products. These findings suggest that horseradish peroxidase catalyzed the one-electron oxidation of acetaminophen to N-acetyl-p-benzosemiquinone imine which preferentially polymerized rather than reacted with GSH. N-Acetyl-p-benzosemiquinone imine may also oxidize 3-(glutathion-S-yl)acetaminophen to form acetaminophen and 3-(glutathion-S-yl)-N-acetyl-p-benzosemiquinone imine. The data indicate that once this conjugate radical is formed it reacts with either N-acetyl-p-benzosemiquinone minine or 3-(glutathion-S-yl)-N-acetyl-p-benzosemiquinone imine via a radical termination mechanism.     

Delayed manifestation of ultraviolet reaction in the guinea-pig caused by anti-inflammatory drugs

1. Exposure of depilated skin of guinea-pig to ultraviolet (u.v.) light for 20 s produces a prolonged inflammatory response.2. The erythaema becomes evident within 15-30 min after the exposure and progressively increases in intensity reaching its maximum by 4-6 hours. The erythaema persists over 24 hours.3. Increase in vascular permeability is biphasic with an early short-lived rise peaking at 0.5 h and a prolonged secondary response peaking at 9-12 h and lasting over 48 hours.4. In presence of aspirin, phenylbutazone and indomethacin, administered prior to u.v. exposure, the inflammatory reaction is partially suppressed, depending upon the dose. The drugs are ineffective in aborting or minimizing the response when given after the inflammation is established. Corticosteroids fail to influence the u.v. inflammation in this test. The significance of these findings is discussed.     

Microcrystals for dissolution rate enhancement of poorly water-soluble drugs

Slight dissolution rates related to poor water-solubility are one of the well-known difficulties to be covered during the development of new drug substances. The poorly water-soluble drug ECU-01, a low molecular enzyme-inhibitor with anti-inflammatory properties for oral administration, shows a poor dissolution rate. This study is intended to enhance the drug dissolution rate by using microcrystals. The common way for micronization is the milling of previously formed larger crystals. However, milling shows several disadvantages as the newly created surfaces are thermodynamically activated due to the high energy input and not naturally grown. In this study microcrystals were not produced using any cutting up techniques, but only by association. Naturally grown microcrystals were prepared by a precipitation method in the presence of stabilizing agents (e.g. gelatin, chitosan, different types of cellulose ethers) followed by spray-drying of the formed dispersion. First the drug was dissolved in acetone and then precipitated by rapid pouring an aqueous solution of the stabilizer into the drug solution. Particularly, cellulose ethers were able to form stable and homogeneous dispersions of microcrystals (mean particle size = 1 microm) showing a tight particle size distribution. By spray-drying, the drug powder was obtained. The dissolution rate is significantly enhanced (common drug: 4% after 20 min/microcrystals 93% after 20 min) due to the large surface, which is hydrophilized by adsorbed stabilizers as shown by the decreased contact angle (65 and 30 degrees, respectively).     

Dissolution rate enhancement by adsorption of poorly soluble drugs on hydrophilic silica aerogels

The aim of this work is to evaluate the feasibility of hydrophilic silica aerogels as drug carriers and to investigate the influence of the aerogels properties on the release rate of poorly water-soluble drugs. Hydrophilic silica aerogels of different densities were loaded with two model drugs, ketoprofen and griseofulvin, by adsorption from their solution in supercritical CO2. It is demonstrated that up to 30 wt% of ketoprofen and 5.4 wt% of griseofulvin can be deposited on hydrophilic aerogels through physical adsorption. The obtained drug-aerogel formulations were characterized by IR- and UV-spectroscopy, X-ray diffraction and scanning electron microscopy. Release kinetics of both drugs were studied in vitro. The release rate of ketoprofen from the drug-aerogel formulation is much faster than that of the corresponding crystalline drugs. The release rate of ketoprofen increases in 500% and that of griseofulvin in 450%, respectively. The reasons for the release enhancement are the enlarged specific surface area of drugs by adsorption on aerogels compared to their crystalline form and the immediate collapse of aerogel network in aqueous media. The dissolution rate of poorly water soluble drugs can be significantly enhanced by adsorption on highly porous hydrophilic silica aerogels.     

重视非甾体抗炎药不良反应的监测及合理应用

非甾体类抗炎药（nonsteroid anti-inflammatory drugs,NSAIDs）是指一大类具有镇痛、抗炎、解热等功能的药物,也是目前临床上应用最广泛的药物之一,全世界每天约有3000万人在使用此类药物.但是,NSAIDs在为亿万患者减轻病痛的同时,也给患者和社会带来了一些不必要的痛苦和经济负担.在美国,由于非甾体类抗炎药的各种不良反应,每年可导致103 000人次需要住院治疗,16500人死亡[1,2].因此,NSAIDs引发的药物不良反应使其在临床的应用受到一定程度的限制.最近,昔布类药物所引发的心血管不良反应事件,使广大患者和医务工作者分外关注NSAIDs的安全性.     

Endotoxin-induced reduction of social investigation by mice: interaction with amphetamine and anti-inflammatory drugs

 Previous studies indicate that some aspects of endotoxin-induced sickness behavior in rats may be mediated by interleukin-1 stimulated events and can be attenuated by corticosteroids, cyclooxygenase inhibitors and the interleukin-1-receptor antagonist. In the current studies, we replicate and extend these findings in adult male mice. A relatively low dose of lipopolysaccharide (LPS; 15 μg/kg, IP) was used to reliably induce a 50–60% reduction in the social investigation of a juvenile conspecific at 2–3 h after injection. Amphetamine (2.0–4.0 mg/kg, IP, 30 min pre-LPS) exacerbated LPS-induced decreases in investigation. Administration of methylprednisolone (10–30 mg/kg, IP), indomethacin (3–30 mg/kg, IP), and ibuprofen (1–100 mg/kg, IP) 1 h before LPS significantly reduced LPS-induced sickness behavior at several doses. Dexamethasone (0.1–10 mg/kg, IP) partially antagonized sickness. Representative flavonoids rohitukine (0.01–100.0 mg/kg, IP) and chrysin (0.01–10 mg/kg, IP) also antagonized LPS-induced deficits in social investigation. These studies replicate and extend previous studies in rat to demonstrate systematic effects of low doses of LPS, antagonism by anti-inflammatory drugs and enhancement of LPS effects by amphetamine. The latter findings are consistent with a modulatory role for adrenergic activation on interleukin-1 release stimulated by endotoxicity. Received: 7 August 1996 / Final version: 13 March 1997     

Effects of anti-inflammatory drugs on the lame walking reaction in adjuvant-induced edematous rats

Acute inflammatory paw edema of rats was formed by the injection of 0.5% Mycobacterium tuberculosis-liquid parraffin suspension into the hind paw, and then the pain threshold of the inflamed paw decreased. At that time, the rats showed a three-legged gait, namely, the lame walking reaction. The reaction was inhibited by acidic nonsteroidal anti-inflammatory drugs, e.g., indomethacin, ibuprofen and aspirin, inhibitors of prostaglandins biosynthesis, at a lower dose level than those in the Randall-Selitto test using yeast edematous rats and in the flection tests using adjuvant arthritic or silver nitrate arthritic rats. On the other hand, basic nonsteroidal anti-inflammatory drugs, e.g., tiaramide HC1, mepirizole and perisoxal citrate, not inhibitors of prostaglandins biosynthesis, were less potent than the acidic nonsteroidal anti-inflammatory drugs in the inhibition of the lame walking reaction. When prostaglandin E2 was injected into the inflamed paw, the inhibitory effects of acidic non-steroidal anti-inflammatory drugs on the reaction disappeared, but those of the basic nonsteroidal anti-inflammatory drugs didn't disappear. Bradykinin had no influence on the effects of both acidic and basic nonsteroidal anti-inflammatory drugs in the inhibition of the reaction. Analgesic evaluation with the lame walking reaction is more sensitive than with the Randall-Selitto or the flection methods. Morphine, pentazocine and acetaminophen inhibited the reaction, and these effects didn't disappear by the injection of prostaglandin E2 into the inflamed paw. These results suggest that prostaglandins play important roles in inflammatory pain, and the lameness test can serve as a new method for evaluating analgesics such as anti-inflammatory drugs and for investigating the mechanism of inflammatory pain.