PEG modification of Amorfrutin B from Amorpha fructicosa increases gastric absorption, circulation half-life and glucose uptake by T3T-L1 adipocytes.

Through a simple PEG-conjugation of the natural product Amorfrutin B, we enhanced its pharmacokinetic profile. The PEGylated molecule displayed significantly improved gastrointestinal absorption (p<0.05) and had a longer systemic circulation life (p<0.05). Oral glucose tolerance study showed PEGylated Amorfrutin B displayed longer protection against oral glucose load compared to Amorfrutin B (p<0.05). It also showed significant improvement in glucose uptake in-vitro by T3T-L1 adipocytes (p<0.05). The PEGylated molecule also showed reduced propensity of crossing the blood brain barrier and accumulating in the brain (p<0.05). It also showed reduced accumulation in the adipose tissue. Preliminary liver and kidney toxicity screening showed no significant alteration in liver or kidney function of Amorfrutin B or its PEGylated form. In conclusion, PEG modification can be an attractive strategy to reduce lipophilicity and enhance pharmacokinetic properties of natural products, derived from traditional medicine.

Lack of dose dependent kinetics of methyl salicylate-2-O-ß-D-lactoside in rhesus monkeys after oral administration.

ETHNOPHARMACOLOGICAL RELEVANCE: Methyl salicylate-2-O-ß-d-lactoside (MSL) is one of the main active components isolated from Gaultheria yunnanensis, which is a traditional Chinese medicine used to treat arthritis and various aches and pains. Pharmacological researches showed that MSL had various effective activities in both in vivo and in vitro experiments. However, the pharmacokinetics features and oral bioavailability of MSL in primates were not studied up to now. AIM: To study the pharmacokinetics of different doses of MSL in rhesus monkeys and investigate the absolute bioavailability of MSL after oral administration. MATERIALS AND METHODS: Male and female rhesus monkeys were either orally administrated with MSL 200, 400 and 800 mg/kg or received an intravenous dose of 20mg/kg randomly. The levels of MSL and salicylic acid (SA) in plasma were simultaneous measured by a simple, sensitive and reproducible high performance liquid chromatography method. RESULTS: Mean peak plasma concentration values for groups treated with 200, 400 and 800 mg/kg doses ranged from 48.79 to 171.83 µg/mL after single-dose oral administration of MSL, and mean area under the concentration-time curve values ranged from 195.16 to 1107.76 µg/mL h. Poor linearity of the kinetics of SA after oral administration of MSL was observed in the regression analysis of the Cmax-dose plot (r(2)=0.812), CL-dose plot (r(2)=0.225) and AUC(0-t)-dose plot (r(2)=0.938). Absolute bioavailability of MSL was assessed to be 118.89 ± 57.50, 213.54 ± 58.98 and 168.72 ± 76.58%, respectively. CONCLUSIONS: Bioavailability of MSL after oral administration in rhesus monkeys was measured for the first time. Pharmacokinetics parameters did not appear to be dose proportional among the three oral doses of treatments, and MSL showed an apparent absolute bioavailability in excess of 100% in rhesus monkeys based on the present study. In addition, a rapid, sensitive and reliable HPLC method was established and demonstrated for the research of traditional Chinese medicine in this study.

Pharmacokinetics of methyl salicylate-2-O-ß-D-lactoside, a novel salicylic acid analog isolated from Gaultheria yunnanensis, in dogs.

Methyl salicylate-2-O-ß-D-lactoside (MSL), a natural salicylate derivative of Gaultheria yunnanensis (Franch.) Rehder (G. yunnanensis), has been shown to provide a beneficial anti-inflammatory effect in animal models. Studies on the pharmacokinetics and bioavailability of MSL can provide both a substantial foundation for understanding its mechanism and empirical evidence to support its use in clinical practice. A simple and sensitive high-performance liquid chromatography (HPLC) method, coupled with ultraviolet analyte detection, was developed for determining the concentration of MSL and its metabolite in beagle plasma. Chromatographic separation was achieved on a Agilent Zorbax SB-C18 column (5 µM,4.6 × 250 mm). The mobile phase consisted of aqueous solution containing 0.1% phosphoric acid and acetonitrile (82:90, v/v), at a flow rate of 1 mL/min. Validation of the assay demonstrated that the developed HPLC method was sensitive, accurate and selective for the determination of MSL and its metabolite in dog plasma. After orally administering three doses of MSL, it could no longer be detected in dog plasma and its metabolite, salicylic acid, was detected. Salicylic acid showed a single peak in the plasma concentration-time curves and linear pharmacokinetics following the three oral doses (r(2) > 0.99). In contrast, only MSL was detected in plasma following intravenous administration. These results will aid in understanding the pharmacological significance of MSL. The developed method was successfully used for evaluation of the oral and intravenous pharmacokinetic profile of MSL in dogs.

The analysis of methyl salicylate and salicylic acid from Chinese herbal medicine ingestion.

This paper presents a multi-drug fatality in which methyl salicylate was ingested. It is presented to inform the toxicological community that a particularly expeditious method of detection for methyl salicylate exists. Previously published methods for the analysis of methyl salicylate include a gas chromatographic-mass spectrometric method and an alkaline/acidic extraction followed by high-performance liquid chromatographic (HPLC) analysis. This article describes a method for analyzing methyl salicylate using HPLC, in which a simple, rapid extraction procedure is used. Using a previously published HPLC method, methyl salicylate and salicylic acid were easily identified in biological specimens. Methyl salicylate and salicylic acid were detected using an extraction solution of acetonitrile coupled with internal standard and then analyzed by HPLC-diode-array detection. Because of its concentrated liquid form, methyl salicylate ingestion can cause rapid onset salicylate toxicity. As the potentially fatal methyl salicylate forms are readily available and easily found on drugstore shelves, the need to rapidly detect and quantitate salicylic acid concentrations that are due to methyl salicylate ingestion may arise. In the case presented, the peripheral blood concentration of salicylic acid from methyl salicylate ingestion was 320 mg/L, and the concentration in gastric contents was 820 mg. It alone was not the cause of death, however. The discovery of the ability to detect and quantitate methyl salicylate was due to its suspected ingestion.

Differential changes in Fos-immunoreactivity at the auditory brainstem after chronic injections of salicylate in rats.

In human, salicylate-induced tinnitus sometimes occurs a few days after its administration, but the chronic effects of salicylate in animal models are not fully known. In this study, we revealed the distribution of active cells in the rat auditory brainstem by staining an activity marker Fos-protein after multiple daily injections of salicylate. Experimental animals were first given five daily doses of sodium salicylate (250 mg/kg, i.p.). On day 6 they were placed inside a sound room for 8 h before sacrifice. Immunohistochemistry showed a significant increase in the number of Fos-positive cells at the inferior colliculus (IC), particularly its central division. At the cochlear nucleus (CN), only a few Fos-stains were found at the dorsal nucleus while no Fos-stain appeared at the ventral nucleus. The scarcity of Fos-stains at the CN reflected more a lack of external sound inputs than an adaptation in Fos-expression. Since Fos-stains in CN could still be induced on day 6 following brief tonal stimulation. Results are consistent with the hypothesis that salicylate-induced tinnitus is a phantom sound perception related to overactivity of cells at the IC.

Pharmacokinetics of salicin after oral administration of a standardised willow bark extract.

OBJECTIVE: To evaluate the pharmacokinetics of salicin and its major metabolites in humans after oral administration of a chemically standardised willow bark extract. METHODS: Willow bark extract corresponding to 240 mg salicin (1,360 mg, 838 micromol) was ingested by ten healthy volunteers in two equal doses at times 0 h and 3 h. Over a period of 24 h, urine and serum levels of salicylic acid and its metabolites, i.e. gentisic acid and salicyluric acid, were determined using reverse-phase high-performance liquid chromatography. Renal excretion rate, elimination half-life and total bioavailability of salicylates were calculated. RESULTS: Salicylic acid was the major metabolite of salicin detected in the serum (86% of total salicylates), besides salicyluric acid (10%) and gentisic acid (4%). Peak levels were reached within less than 2 h after oral administration. Renal elimination occurred predominantly in the form of salicyluric acid. Peak serum levels of salicylic acid were on average 1.2 mg/l, and the observed area under the serum concentration time curve (AUC) of salicylic acid was equivalent to that expected from an intake of 87 mg acetylsalicylic acid. CONCLUSION: Willow bark extract in the current therapeutic dose leads to much lower serum salicylate levels than observed after analgesic doses of synthetic salicylates. The formation of salicylic acid alone is therefore unlikely to explain analgesic or anti-rheumatic effects of willow bark.

Effect of Tamarindus indica L. on the bioavailability of aspirin in healthy human volunteers.

The influence of Tamarindus indica L. fruit extract incorporated in a traditional meal on the bioavailability of aspirin tablets 600 mg dose was studied in 6 healthy volunteers. There was a statistically significant increase in the plasma levels of aspirin and salicylic acid, respectively, when the meal containing Tamarindus indica fruit extract was administered with the aspirin tablets than when taken under fasting state or with the meal without the fruit extract. The Cmax, AUC0-6h and t1/2 for aspirin increased from 10.04 +/- 0.1 mg/ml to 28.62 +/- 0.21 mg/ml (P < 0.05); 14.03 +/- 0.11 mg/ml.h to 86.51 +/- 0.21 mg/ml.h (P < 0.085) and 1.04 +/- 0.12 h to 1.50 +/- 0.44 h (P < 0.05) respectively. There was no change in the tmax (0.50 +/- 0.17 h) but there was a decrease in the kel from 0.633 +/- 0.22 to 0.463 +/- 0.29 (P < 0.05). Similarly, the Cmax, AUC0-6h and kel for salicylic acid rose from 43.84 +/- 0.21 mg/ml to 68.19 +/- 0.71 mg/ml (P < 0.05); 171.59 +/- 0.07 mg/ml.h to 266.22 +/- 0.21 mg/ml/.h (P < 0.05) and 7.37 +/- 0.29 to 19.30 +/- 0.21 (P < 0.05), respectively. The tmax decreased from 2.0 +/- 0.18 h to 1.0 +/- 0.08 h (P < 0.05) and t1/2 from 0.25 +/- 0.21 h to 0.184 +/- 0.11 h (P < 0.05). The study has indicated that Tamarindus indica L. fruit extract significantly increased the bioavailability of aspirin.

Effect of multiple-dose activated charcoal on the clearance of high-dose intravenous aspirin in a porcine model.

STUDY OBJECTIVE: To study the effect of multiple-dose activated charcoal (MDAC) on salicylate clearance in pigs given high-dose i.v. aspirin. DESIGN: In a crossover design, six fasted pigs received 300 mg/kg i.v. aspirin followed by no treatment or MDAC (1 g/kg hourly for 6 doses by gastrostomy). Serum salicylate samples were obtained every 30 minutes for 6 hours. RESULTS: The mean peak salicylate concentrations were 47.4 +/- 6.2 mg/dL and 48.4 +/- 3.9 mg/dL (P = .74), and the areas under the time-serum salicylate concentration curve over 6 hours were 171,000 +/- 24,000 mg.minute/L and 188,000 +/- 18,000 mg.minute/L for the control and treatment arms, respectively (P = .22). This study had a 90% power to detect a 30% difference between arms. CONCLUSION: MDAC does not enhance the clearance of salicylate after administration of high-dose i.v. aspirin.

Poisoning due to Chinese proprietary medicines.

1. To determine the toxic potentials of those Chinese proprietary medicines (CPM) which are commonly used for self-poisoning by adults in Hong Kong, all patients admitted to four of the eight general medical wards at the Prince of Wales Hospital between January 1988 and December 1993 were retrospectively studied. 2. There were 54 women and 17 men with their age ranging from 15 to 86 years. Twenty-three subjects (32%) also took alcohol, chemicals or drugs. Of the 51 subjects (72%) who had taken topical medicaments, 22 had no symptoms while 28 had minor features of gastrointestinal irritation (n = 26), mild (n = 2) or severe (n = 1) salicylate poisoning. Of the 17 subjects (24%) who had taken CPM tablets/capsules, nine had mild symptoms including nausea/vomiting and drowsiness. The three remaining patients (4%) who had ingested liquid CPM preparations were asymptomatic. Elevated plasma salicylate or paracetamol concentrations (> 0.1 mmol l-1) were found in some patients who had taken topical medicaments and CPM tablets/capsules, respectively. All the 71 patients completely recovered. 3. Most of the CPM used for self-poisoning in Hong Kong were of low to moderate toxicity except for those containing wintergreen oil (methyl salicylate).

Carbamazepine-salicylate interaction in normal and uremic sera: reduced interaction in uremic sera.

Displacement of phenytoin and valproic acid by salicylate have been described. We studied carbamazepine-salicylate interactions in normal and uremic sera, which have not been studied. Salicylate caused significant displacement of carbamazepine from protein binding, leading to higher concentrations of free carbamazepine. The concentrations of free carbamazepine were always significantly higher in uremic sera than in normal sera. However, when uremic sera were supplemented with both carbamazepine and salicylate, we observed a much lower displacement of carbamazepine and only a slight increase in free carbamazepine concentration. Treatment of uremic sera with activated charcoal corrected the binding deficiency for carbamazepine. Known uremic compounds like hippuric acid and indoxyl sulphate can only partly explain the observed displacement of carbamazepine in uremic sera. We conclude that salicylate displaces carbamazepine from protein binding in normal sera, but this interaction is significantly reduced in uremic sera.

Salicylate-induced abnormal activity in the inferior colliculus of rats.

The evaluation of the spontaneous activity of 471 units from the external nucleus of the IC revealed that salicylate induces an increase of the spontaneous activity and the emergence of a bursting type of activity longer than 4 spikes. For sharply tuned units, the affected cells were from the frequency range of 10-16 kHz, which corresponds to the behaviorally measured pitch of salicylate-induced tinnitus in rats. An exogenous calcium supplement, provided under the conditions shown to attenuate the behavioral manifestation of salicylate-induced tinnitus, abolished the modification of the spontaneous activity induced by salicylate. Finally, profound changes of activity were observed for cells not responding to contralateral sound. We propose that the observed long bursts of discharges represent tinnitus-related neuronal activity. The results are consistent with the hypothesis that GABA-mediated disinhibition is involved in the processing of tinnitus-related neuronal activity.

Reduced in vitro displacement of valproic acid from protein binding by salicylate in uremic sera compared with normal sera. Role of uremic compounds.

Limited studies indicate increased free fraction of valproic acid in uremia. One study also described displacement of valproic acid from protein binding by salicylate in children with epilepsy. The authors studied in vitro interaction of valproic acid and salicylate in uremic sera and compared their results with same interactions in normal sera. As expected, the concentrations of free valproic acid were always significantly higher in uremic sera compared with normal sera. When uremic sera were supplemented with both valproic acid and salicylate, a much lower displacement of valproic acid by salicylate was observed, compared with the effects observed in normal sera. Treatment of uremic sera with charcoal removed those uremic compounds, and the concentration of free valproic acid in charcoal-treated uremic sera were comparable to the concentrations observed in normal sera. When uremic compounds were extracted from charcoal with methanol, lyophilized, and added to normal serum, an increase in free valproic acid concentration in normal serum was observed, indicating that uremic compounds, rather than altering albumin structure, are responsible for elevated free valproic acid concentration in uremia. However, uremic extract failed to produce any further displacement of valproic acid in normal serum in the presence of salicylate. The authors concluded that uremic compounds are responsible for elevated free valproic acid concentrations, but the displacement of valproic acid by salicylate in uremic sera are less remarkable compared with such effect in normal sera.

Does salicylic acid increase the percutaneous absorption of diflucortolone-21-valerate?

The percutaneous absorption of diflucortolone-21-valerate (DFV) and its effect on the pituitary adrenal system were investigated during large skin area treatment (20 g ointment twice a day for 8 days) of two groups of healthy volunteers with Nerisona and Nerisalic ointment, respectively. Plasma levels of diflucortolone, cortisol and dehydroepiandrosterone (DHEA) were measured in both groups whereas plasma levels of salicylic acid were measured additionally in volunteers treated with Nerisalic. No differences, neither in percutaneous absorption of DFV nor in effects on cortisol and DHEA were found between the two treatment groups. There was a slight reduction in cortisol levels under both treatments, but the circadian rhythm was not disturbed. Mean salicylic acid plasma levels under high-dose topical Nerisalic treatment were about 50-fold below levels where toxicity may be expected.

The effect of nimodipine on salicylate ototoxicity in the rat as revealed by the auditory evoked brain-stem response.

Experiments have been performed to investigate the ototoxic effects of sodium salicylate administration in anaesthetised rats as recorded by the auditory evoked brain-stem response (AEBR). Sodium salicylate (300 mg kg-1 i.p.) produced time-dependent increases in hearing threshold and decreases in the four principle peaks of the AEBR. Maximum responses were obtained at 4 h post-administration and were highly significant (P < 0.001). In a further series of experiments nimodipine, a calcium channel antagonist which has been suggested as a potential therapy for tinnitus, was administered at a dose of 2 mg kg-1 s.c. at the same time as sodium salicylate. This had no effect on the changes in hearing threshold. However, it did reduce the decrease in latencies of three of the four peaks of the AEBR, such that only the decrease in latency of the first peak was significantly different when compared to the pre-injection control latency (P < 0.01). We believe that these findings show specific neurophysiological correlates of salicylate ototoxicity. Since salicylate intoxication is used as the method for inducing tinnitus in animal models, the changes in the AEBR may provide an objective measure by which potential therapeutic intervention may be tested.

Significant role of aspirin use in patients with esophagitis.

This study determines objectively the extent of nonsteroidal anti-inflammatory drug (NSAID) use in upper gastrointestinal (GI) mucosal acid-peptic diseases by supplementing the conventional interview with two tests of current aspirin (ASA) use--high-performance liquid chromatography (HPLC) for the presence of salicylates in serum and platelet cyclooxygenase activity, which detects ASA use within 5 days of testing. Of 186 consecutive patients undergoing upper endoscopy, 62% of 55 patients with esophagitis had evidence of current NSAID use, vs. 26% of 42 control patients with normal endoscopy (p less than 0.001), 12% of 17 patients with recently healed peptic ulcer (p less than 0.001), and 36% of 25 patients who had an active peptic ulcer (p less than 0.05), five of whom had concomitant esophagitis. Another 52 patients were ineligible for this analysis. Testing for platelet cyclooxygenase activity uncovered 26% more ASA users than history alone. In considering age, sex, smoking and drinking habits, arthritis, and ASA use by logistic regression, ASA use was the only factor contributing to esophagitis; ASA could not be further associated with severity, stricture or symptoms, however. In these patients, 95% of NSAID use was chronic, and 84% of that was ASA. These data show a previously unreported, strong association of ASA use with esophagitis, which suggests that ASA may be a significant factor in the resistance of esophagitis to current therapies as well as the frequently rapid relapse after therapy is withdrawn.

Effects of paracetamol and aspirin on neural activity of joint mechanonociceptors in adjuvant arthritis.

1. The effects of paracetamol and lysine acetylsalicylate (L-AS) on high-threshold mechanonociceptors have been investigated by recording neural activity from the inflamed ankle joint in anaesthetized rats with mild adjuvant-induced monoarthritis. 2. Paracetamol (50 mg kg-1, i.v.) and L-AS (100 mg kg-1, i.v., equivalent to 50 mg kg-1 aspirin) both caused a maximal reduction of about 40% in mechanically-evoked discharge and of 30% in ongoing (spontaneous) activity by about 15 min after the injection: a second dose of either drug did not have any significant additional effect on discharge. 3. The prostanoid IP receptor agonist, cicaprost (0.1-0.5 micrograms), increased both mechanically-evoked and ongoing discharge to pre-paracetamol levels when injected close-arterially 30-50 min after paracetamol, whereas prostaglandin E2 (PGE2) was relatively ineffective at restoring activity. 4. The results suggest that prostacyclin (PGI2) contributes to the sensitization of high-threshold joint mechanonociceptors in adjuvant-induced monoarthritis, and that paracetamol and L-AS both act to reduce discharge by inhibiting the synthesis of prostacyclin in the joint capsule. 5. Paracetamol has a direct peripheral action affecting joint capsule mechanonociceptors in rat adjuvant-induced arthritis which is very similar to that of the soluble aspirin preparation, L-AS. These findings, together with the existing literature concerning the anti-arthritic effects of paracetamol, are relevant to the treatment of chronic inflammatory disorders such as rheumatoid arthritis.

Severe metabolic acidosis and "muti" (traditional herbal medicine) ingestion in young children.

Twenty infants and young children admitted with severe metabolic acidosis and a positive history of 'muti' ingestion were investigated. All had accompanying gastroenteritis and significant dehydration. Biochemical data was diagnostic of high anion/gap metabolic acidosis in the majority (70 per cent). Further biochemical data indicated that lactic acidosis and pre-renal azotaemia resulting from severe hypovolaemia were likely causes of the high anion GAP metabolic acidosis. There was no evidence to suggest that the ingested muti per se was associated directly with the acidosis or acute renal failure seen in these children.

Plasma and synovial fluid concentrations of salicylic acid and its metabolites in patients with joint effusions.

Equilibration of salicylic, salicyluric and gentisic acids between plasma and synovial fluid (SF) was measured in 36 patients receiving chronic salicylate therapy and from whom SF was required for diagnostic purposes. Gentisic and salicyluric acids equilibrated completely, while SF salicylic acid concentration was less than that in plasma. The presence of significant gentisic acid concentrations in SF could contribute to the therapeutic response to chronic salicylate therapy, since its antiinflammatory effect is even greater than that of acetylsalicylic acid.

Effect of antacid and ascorbic acid on serum salicylate concentration.

To determine the effect of antacid or ascorbic acid administration on plateau serum salicylate concentrations, nine healthy subjects were given each of the following treatments by balanced block design: choline salicylate (equivalent to 3.76 or 5.62 Gm/day of aspirin); choline salicylate plus magnesium-aluminum hydroxide (120 ml/day); or choline salicylate plus ascorbic acid (3 Gm/day). In subjects developing a control serum salicylate level above 10 mg/dl, antacid administration produced a decrease in serum salicylate level (mean 19.8 mg/dl vs. 15.8 mg/dl) (P less than 0.01). Ascorbic acid administration was not associated with a significant change in serum salicylate. The reduction in serum salicylate following antacid appears to be due to antacid-induced alkalinization of the urine with resultant increase in renal salicylate clearance. Antacid administration should be considered a potential cause of altered serum salicylate concentration in patients receiving large doses of salicylate.