Pharmacokinetics of repeated sodium salicylate administration to laying hens: evidence for time dependent increase in drug elimination from plasma and eggs

Salicylates were the first non-steroid anti-inflammatory drugs (NSAIDs) to be used in any species and are still widely used in humans and livestock. However, the data on their pharmacokinetics in animals is limited, especially after repeated administration. Evidence exist that in chickens (Gallus gallus) salicylate (SA) may induce its own elimination. The aim of this study was to investigate salicylate pharmacokinetics and egg residues during repeated administration of sodium salicylate (SS) to laying hens. Pharmacokinetics of SA was assessed during 14 d oral administration of SS at daily doses of 50 mg/kg and 200 mg/kg body weight to laying hens. On the 1st, 7th and 14th d a 24 h-long pharmacokinetic study was carried out, whereas eggs were collected daily. Salicylate concentrations in plasma and eggs were determined using high-performance liquid chromatography with ultraviolet detection and pharmacokinetic variables were calculated using a non-compartmental model. Mean residence time (MRT), minimal plasma concentration (Cmin, C16h) and elimination half-life (T1/2el) of SA showed gradual decrease in layers administered with a lower dose. Total body clearance (ClB) increased. Layers administered with the higher dose showed a decrease only in the T1/2el. In the low dose group, SA was found only in the egg white and was low throughout the experiment. Egg whites from the higher dose group showed initially high SA levels which significantly decreased during the experiment. Yolk SA levels were lower and showed longer periods of accumulation and elimination. Repeated administration of SS induces SA elimination, although this effect may differ depending on the dose and production type of a chicken. Decreased plasma drug concentration may have clinical implications during prolonged SS treatment.

Attenuation of acute plasma cortisol response in calves following intravenous sodium salicylate administration prior to castration

Pain associated with castration in cattle is an animal welfare concern in beef production. This study examined the effect of oral aspirin and intravenous (i.v.) sodium salicylate on acute plasma cortisol response following surgical castration. Twenty bulls, randomly assigned to the following groups, (i) uncastrated, untreated controls, (ii) castrated, untreated controls, (iii) 50 mg/kg sodium salicylate i.v. precastration and (iv) 50 mg/kg aspirin (acetylsalicylic acid) per os precastration, were blood sampled at 3, 10, 20, 30, 40, 50 min and 1, 1.5, 2, 4, 6, 8, 10 and 12 h postcastration. Samples were analyzed by competitive chemiluminescent immunoassay and fluorescence polarization immunoassay for cortisol and salicylate, respectively. Data were analyzed using noncompartmental analysis, a simple cosine model, anova and t-tests. Intravenous salicylate V(d(ss)) was 0.18 L/kg, Cl(B) was 3.36 mL/min/kg and t(1/2 lambda) was 0.63 h. Plasma salicylate concentrations above 25 microg/mL coincided with significant attenuation in peak cortisol concentrations (P = 0.029). Peak salicylate concentrations following oral aspirin administration was <10 microg/mL and failed to attenuate cortisol response. Once salicylate concentrations decreased below 5 microg/mL, cortisol response in the castrated groups was significantly higher than uncastrated controls (P = 0.018). These findings have implications for designing drug regimens to provide analgesia during routine animal husbandry procedures.

Dermatopharmacokinetics of salicylate following topical injection in rats: Effect of osmotic pressure and injection volume on salicylate disposition

Using advanced topical formulations containing potential chemical enhancer(s) or physical penetration-enhancing tools capable of delivering entrapped drug(s) directly into skin tissues with little influence of the stratum corneum barrier, local and systemic drug disposition may be markedly similar to direct injection into the skin and muscle. The objective of this study is to investigate the dermatopharmacokinetics and systemic drug disposition after topical application and topical injection. Salicylate (SA) disposition in the skin and muscle as administration sites, and in the systemic circulation were evaluated following intracutaneous (i.c.) injection of an isotonic solution of SA-Na (dose; 3.08 micromol). Subcutaneous (s.c.) and intramuscular (i.m.) injection were also evaluated for comparison. Dermatopharmacokinetics and systemic disposition of SA after i.c. and s.c. injections were analyzed using a 4-compartment model consisting of skin, muscle, and central and peripheral compartments, whereas SA disposition after i.m. injection was analyzed using a 3-compartment model consisting of muscle, and central and peripheral compartments. Moreover, the absorption rate constant of SA after i.c. injection (0.073 min(-1)) was slightly lower than that after s.c. injection (0.083 min(-1)), and much lower than that after i.m. injection (0.327 min(-1)). In addition, higher osmolarity and a larger volume of SA-Na injectant increased the retention of SA in the skin and decreased the absorption rate to the systemic circulation after i.c. injection. The effect of injection volume on SA disposition after i.c. injection was not so marked compared with that of osmotic pressure. These results are useful to design an injection-type topical delivery system.

Influence of plasma protein on the potencies of inhibitors of cyclooxygenase-1 and -2

It is widely believed that the potencies of nonsteroid anti-inflammatory drugs (NSAIDs) as inhibitors of cyclooxygenase (COX) are influenced by protein binding in the extracellular fluid, since NSAIDs are bound to circulating albumin by well over 95%. This is an important point because the protein concentrations in synovial fluid and the central nervous system, which are sites of NSAID action, are markedly different from those in plasma. Here we have used a modified whole-blood assay to compare the potencies of aspirin, celecoxib, diclofenac, indomethacin, lumiracoxib, meloxicam, naproxen, rofecoxib, sodium salicylate, and SC560 as inhibitors of COX-1 and COX-2 in the presence of differing concentrations of protein. The potencies of diclofenac, naproxen, rofecoxib, and salicylate, but not aspirin, celecoxib, indomethacin, lumiracoxib, meloxicam, or SC560, against COX-1 (human platelets) increased as protein concentrations were reduced. Varying protein concentrations did not affect the potencies of any of the drugs against COX-2, with the exception of sodium salicylate (A549 cells). Clearly, our findings show that the selectivity of inhibitors for COX-1 and COX-2, which are taken to be linked to their efficacy and side effects, may change in different extracellular fluid conditions. In particular, selectivity in one body compartment does not demonstrate selectivity in another. Thus, whole-body safety or toxicity cannot be linked to one definitive measure of COX selectivity.

Disposition of sodium salicylate, flunixin and meloxicam after intravenous administration in broiler chickens

Three nonsteroidal anti-inflammatory drugs (NSAIDs) [sodium salicylate, flunixin (FLU) and meloxicam (MEL)] were administered intravenously to broiler chickens. Plasma concentrations were determined by high-performance liquid chromatography methods and pharmacokinetic parameters were calculated. After intravenous administration of sodium salicylate (50 mg/kg), FLU (1.1 mg/kg) and MEL (0.5 mg/kg), these drugs were eliminated from plasma with a mean half-life of 04.04, 05.45 and 03.20 h, respectively. Apparent volumes of distribution (0.39, 0.08 and 0.12 L/kg, respectively) indicated that tissue distribution was limited for the three drugs. Total body clearance was 70 mL/h.kg for sodium salicylate and 10 and 25 mL/kg.h for FLU and MEL, respectively. Based on the pharmacokinetic parameters these NSAIDs may offer possibilities for treatment of various conditions in chickens.

Targeting of salicylate to skin and muscle following topical injections in rats

The process of systemic absorption and tissue targeting efficacy of salicylate (SA) following intracutaneous (i.c.), subcutaneous (s.c.) and intramuscular (i.m.) injections of its sodium salt in rats were evaluated by determining the drug concentration at the injection site and surrounding tissues. After i.c. and s.c. injections, SA was absorbed into the systemic circulation from the muscular vessels as well as the cutaneous or subcutaneous vessels beneath the injection site, and the AUC of the drug in the muscle was extremely high. Following i.m. injection, SA was rapidly absorbed into the systemic circulation mostly from the muscular vein. These results suggested that i.c. and s.c. injections have high degrees of targeting efficacy to the muscle, whereas i.m. injection is not appropriate for drug retention in muscle. In contrast, most of the topically applied drug was absorbed from the cutaneous vessels, and little drug migration to the muscle was observed. Thus, the skin pharmacokinetics of SA after i.c. injection was also markedly different from those after topical application on the skin. These results suggested that the i.c. and s.c. injections may be a good means to improve the targeting ability of drugs to the muscle as well as the skin.

Oxyradical generation after resuscitation of hemorrhagic shock with blood or stroma-free hemoglobin solution

Hypovolemic states are characterized by inadequate tissue perfusion; when this state is reversed, the reintroduction of oxygen is accompanied by the excess generation of oxyradicals and these, in turn, may cause "reperfusion injury" in susceptible tissues. When hemoglobin solution is used to resuscitate the hypovolemic state, the generation of oxyradicals may be enhanced by catalytic means. The generation of oxyradicals was estimated in dogs subjected to the acute removal of 35 ml/Kg blood, and resuscitated 45 mins thereafter with an equal volume of either autologous blood (Group I, n = 6) or 6% stromafree hemoglobin solution (S.F.H.S.) (Group II, n = 6). Hepatic and pancreatic enzymes were measured in blood drawn at intervals. The hypovolemic state was characterized by profound hypotension which was reversed by resuscitation. Oxyradical generation in arterial blood samples, drawn at various times, was estimated by the generation of oxidation products (2,3- and 2,5-dihydroxybenzoic acid) of exogenously administered sodium salicylate, determined by HPLC in plasma samples extracted with diethyl ether. Salicylate oxidation products rose significantly above the baseline value in Group I dogs, whereas they rose 5-6-fold higher than the baseline values in those of Group II. The actual values attained and the increments were significantly (p < .05) greater in Group II than in Group I. In the group resuscitated with S.F.H.S., catalytically active iron concentration in plasma also rose 10-12-fold higher and was associated with spuriously elevated levels of gamma-glutamyl transferase due to interference with the assay. These findings are consistent with the hypothesis that blood-resuscitation of hypovolemic shock is accompanied by oxyradical generation of a modest degree; in contrast, S.F.H.S.-resuscitation introduces catalytically active iron and is accompanied by oxyradical generation of a significantly greater degree.

Bovine acute mastitis: effects of intravenous sodium salicylate on endotoxin-induced intramammary inflammation

Effects of the nonsteroidal antiinflammatory agent sodium salicylate on endotoxin-induced mastitis were evaluated in lactating cows. Escherichia coli endotoxin was administered to a mammary quarter 1 h after initiation of a 12-h i.v. infusion of sodium salicylate. Milk SCC, BSA concentrations in milk, mammary inflammation, rectal temperature, appetite, milk production, and plasma and lymph PGF2 alpha were monitored. Gross mammary inflammation was not reduced by salicylate infusion, nor did sodium salicylate prevent increased milk SCC or BSA concentrations in milk, although treatment tended to decrease the magnitude of these responses. Sodium salicylate decreased subcutaneous abdominal vein PGF2 alpha metabolite, and PGF2 alpha metabolite tended to be reduced in lymph during the acute phase of inflammation. The increased rectal temperature after endotoxin infusion was reduced in cows treated with sodium salicylate. Appetite was reduced after endotoxin infusion in untreated cows and those treated with sodium salicylate. Milk production declined after endotoxin challenge in all cows. Although sodium salicylate did not substantially reduce mammary inflammation, it had an antipyretic effect and reduced PGF2 alpha metabolite in mammary blood.

Evidence of significant absorption of sodium salicylate from urinary bladder of rats

The hypothesis that weakly acidic drugs are reabsorbed from the urinary bladder was tested using adult female Fischer rats. Bladder reabsorption would have direct implications for pharmacokinetic data analysis of compounds with significant renal excretion. Sodium salicylate (SA) undergoes extensive renal excretion in the rat, and was selected as the model compound. Methodology was developed to administer an intravesical dose to a rat via a transurethral catheter. The barrier function and the integrity of the bladder urothelium were examined by light and electron microscopy, and by monitoring leakage of [14C] inulin (MW 5000) and fluorescein (MW 376). Using these methodologies, we found that urothelial integrity was maintained in about 80% of the animals. Animals that showed tissue damage were excluded from the study. In the pharmacokinetic experiments, one group of animals received an i.v. dose of SA (1.5 or 3 mg/kg), the second group received an intravesical dose of 30 mg/kg (approximately 0.3 ml) and the third group received concomitantly an i.v. tracer dose of [14C] SA and an intravesical dose of unlabeled SA (30 mg/kg). The intravesical dose was removed after 90 min. The intravesical administration of SA produced maximal blood concentrations of 10.8 +/- 5.6 micrograms/ml (mean +/- S.D., n = 10) at 90 to 100 min. The fraction of the intravesical dose recovered after 90 min was between 45 and 75%, which indicates an upper limit of 25 to 55% loss by processes including absorption. The bioavailability of the intravesical dose, calculated from the blood data and the clearance of the i.v. doses, was between 4 and 23% and averaged about 13%.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of age on salicylate pharmacokinetics in humans

The pharmacokinetics of salicylate after a single oral solution dose of 600 mg of sodium salicylate were investigated in 22 male subjects. Subjects were healthy nonsmokers and were not taking any regular medication. The plasma concentration and urinary excretion of salicylic acid and its metabolite, salicyluric acid, as well as the urinary excretion of salicyl glucuronides were determined. Urinary recovery essentially accounted for the administered dose and was not influenced by age, nor was the apparent oral clearance of salicylic acid. Assuming no presystemic elimination, it could be concluded that systemic availability is unaffected by age. An increase in the apparent volume of distribution, Varea, and a decrease in the maximum plasma salicylic acid concentration with age were observed. Renal clearance of salicyluric acid decreased significantly with age and was found to correlate significantly with creatinine clearance. The authors conclude that age does not have a major influence on salicylate disposition in healthy adult men.

Effects of sodium salicylate on evoked-response measures of hearing

The effects of sodium salicylate on auditory sensitivity, frequency selectivity, and temporal resolution were monitored in chinchillas using evoked responses recorded from the inferior colliculus. Administration of sodium salicylate (450 mg/kg/day for 5-15 days) resulted in serum salicylate levels of 25-50 mg/100 ml. The salicylate administration caused elevation of evoked response thresholds (up to 30 dB), mainly at the high frequencies. Frequency selectivity, as estimated by the Q10 dB value of evoked-response tuning curves, was poorer at 4 kHz during drug administration than during the no drug (control) condition. Temporal resolution, as estimated by recovery from forward masking was not significantly poorer during salicylate administration than before administration. However, there was a trend toward longer recovery in animals with large threshold shifts. These results are consistent with models suggesting that salicylate affects the auditory system at the level of the organ of Corti. They also suggest that while the changes in hearing that occur after salicylate administration are consistent with those seen in sensorineural hearing loss, the changes in hearing in the chinchilla are small enough to preclude the use of the drug as a practical model for sensorineural loss.

Inhibition of cyclooxygenase-independent platelet aggregation by sodium salicylate

The effect of acetylsalicylic acid (ASA) on platelet aggregation (PA) and thromboxane A2 (TxA2) formation was investigated in vitro and ex vivo after 1 g or 300 mg ASA administration to healthy subjects. 50-100 microM ASA inhibited PA by single aggregating agent such as platelet aggregating factor (PAF) or epinephrine and reduced to less than or equal to 5% of control platelet TxB2 formation, but did not influence PA by epinephrine plus PAF. The latter was inhibited by increasing ASA concentration. In samples incubated with 100 microM ASA and stimulated with epinephrine plus PAF, PA could be inhibited by the addition of 100-300 microM sodium salicylate. After 300 mg-1 g ASA administration to healthy subjects, the inhibition of PA by epinephrine plus PAF was more marked by highest doses of ASA. This study suggests that aspirin inhibits PA with a cyclooxygenase-independent mechanism; this effect is mediated, at least in vitro, by salicylic acid.

[Binding ability of serum albumin in thermal burns]

Binding ability of blood serum albumin was decreased in patients with thermic burns as well as in rats with burns. Loss of this albumin property did not depend on decrease of its content in blood serum; in the patients with burns the decrease in albumin binding ability correlated with development of encephalopathic symptoms. After treatment of blood serum from experimental animals with hemosorbent the blood serum binding ability was distinctly restored in vitro. At the same time, hemosorption did not affect the binding ability of blood plasma in patients with burns. Importance of alterations in binding ability of blood serum albumin for development of acute burns toxemia is discussed.

Enhancement by sodium salicylate of the blood glucose lowering effect of chlorpropamide-drug interaction or summation of similar effects?

The ability of sodium salicylate (3 g) to enhance the blood glucose lowering action of chlorpropamide (200 mg) has been confirmed in healthy male volunteers who received an oral test dose of 50 g glucose. Salicylate raised the plasma concentration of insulin and lowered that of cortisol but did not alter the concentration of chlorpropamide. The area under the blood glucose concentration-time curve was used as the measure of drug response and the significance of drug effects was assessed by analysis of variance. In one study on five volunteers the effect of combining salicylate and chlorpropamide was additive. In a second study on six volunteers 200 mg chlorpropamide, 3 g sodium salicylate and 100 mg chlorpropamide + 1.5 g salicylate were equi-effective. The enhancement of chlorpropamide action by salicylate in this single dose study is consistent with the summation of similar effects. It is not necessary to postulate an interaction.

The acid-base balance during the time course of endotoxin fever and sodium salicylate antipyresis in the rabbit

Blood acid-base balance in sodium salicylate antipyresis was investigated in adult rabbits at ambient temperature of 21.5 +/- 0.5 degrees C. The experimental fever elicited by iv injection of lipopolysaccharide Escherichia coli 1 microgram/kg/ was accompanied by a slight metabolic acidosis. A decrease in pH by 0.09 and HCO3- by 4.8 mEq/1 was noticed during the rising phase of pyrogen fever. There were no concomitant changes in blood PCO2 during that period of time. Although the concentrations of HCO3- were decreasing till the end of the experiment, the parallel falls in PCO2 led to a partial compensation of the noticed acidosis. Pretreatment with 200 mg/kg of sodium salicylate /an hour's iv infusion/reduced the febrile response by 42% and completely reversed the postpyrogen changes in pH and HCO3-. The falls in PCO2 during antipyresis, however, were similar to those observed in febrile rabbits. Possible mechanisms by which sodium salicylate could affect the pyrogen-induced disturbances of acid-base balance are being considered.

The efficacy and pharmacokinetics of sodium salicylate in post-operative dental pain

Sodium salicylate, 537 mg and 1074 mg were compared in a double-blind cross-over study in 24 patients with post-operative pain following removal of impacted lower third molars. No significant analgesic effect was observed after either dose of sodium salicylate, either overall or at any time point during the 5 h investigation period. Peak plasma concentrations of salicylate after 537 mg were observed at 30 min after dosage, whereas peak plasma salicylate concentrations after 1074 mg sodium salicylate occurred at 45 min after dosage.

Simultaneous analysis of 1-beta-D-arabinofuranosylcytosine, 1-beta-D-arabinofuranosyluracil and sodium salicylate in biological samples by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic column switching system is described for the rapid and complete separation of 1-beta-D-arabinofuranosylcytosine (Ara-C), 1-beta-D-arabinofuranosyluracil (Ara-U) and sodium salicylate using an internal standard of sodium cefmetazole. The system is highly selective and separates these compounds from interfering compounds commonly in biological matrices. The system was tested by following the pharmacokinetics of Ara-C after rectal administration in the presence of sodium salicylate which is an aid to drug absorption. The chromatographic system is also suitable for monitoring levels of Ara-C and its metabolite Ara-U after intravenous administration of Ara-C.

[Effect of bacterial endotoxin on gastric emptying and on passive absorption of salicylate in the small intestine]

The salicylate content in blood plasma after its administration into the stomach and small intestine during experimental endotoxemia in mice has been measured. In early stages of intoxication gastric evacuation was fairly slow. Histamine increased, while its antagonist pyrilamine significantly reduced the observed disorder. In the last stages of intoxication, passive absorption in the small intestine increased. Administration of histamine, serotonin and ciproheptadine did not produce any essential effect on the salicylate transport across the intestinal wall.

Salicylate ototoxicity in the chinchilla: a behavioral and electron microscope study

Normal audiograms were obtained from a group of behaviorally conditioned chinchillas. Following this the animals were injected with sodium salicylate. Temporary hearing losses were measured 1 1/2 hours after treatment. Animals were anesthetized and blood samples taken to determine salicylate levels. The animals were then decapitated and the temporal bones were examined by SEM and TEM. No morphological correlate was seen for temporary hearing losses which were generally in the neighborhood of 30-40 dB.

Plasma levels of aspirin following effervescent and enteric coated tablets, and their effect on platelet function

Single doses of effervescent tablets (1200 mg) and enteric coated (EC) tablets (1300 mg and 650 mg) of acetylsalicylic acid (aspirin, ASA) were given to healthy volunteers in random order. Plasma ASA and salicylic acid (SA) levels were measured and concurrent in vitro measurements of the volunteers' platelet aggregation were carried out. The effervescent preparation resulted in peak ASA concentrations of 17-40 mg/l, achieved 20 to 30 min after a 1200 mg dose, whereas peak ASA levels of 0.01-0.37 mg/l were observed 4-6 h after a 650 mg dose of the EC preparation. With all the aggregating agents that were added to the test system maximum inhibition of platelet aggregation (about 50% of pre dose levels) was seen 1.0 h after the effervescent ASA dose, and persisted to at least 24 h, but with the EC preparation not until 24 h, at which time the degree of inhibition was also about 50% of pre-dose levels. A 1.0 g dose of sodium salicylate had no effect on in vitro platelet function. It was concluded that mean plasma levels of ASA of less than 0.25 mg/l are sufficient to depress aggregation by approximately 50%. A low dose of ASA taken daily either as effervescent ASA or EC ASA, significantly inhibits platelet aggregation and so may reduce the risk of ischaemic episodes in susceptible patients.

The effect of sodium salicylate on the rat embryo in culture: an in vitro model for the morphological assessment of teratogenicity

The optimum teratogenic dose of subcutaneously administered sodium salicylate was determined in vivo at 9.5 days of gestation. Fetuses from rats injected with this dose at 9.5 days were examined at 11.5 days and its propensities for producing resorption as well as deformities noted. Next, maternal serum levels 3-3.5 hours and 18.5 hours after salicylate injection were determined. Having established the feasibility of determining an effect due to salicylate at 11.5 days, after injection at 9.5 days, the following experiments were performed in vitro in animals cultured between 9.5 and 11.5 days by the method of New et al. (1976a): (1) Sodium salicylate was added to the culture serum, at levels equivalent to those obtained 3-3.5 hours after maternal injection of the optimum teratogenic dose, for 24 of the 48 hours culture period. (2) Rats were cultured for the first 24 hours of the 48 hours culture period in serum taken from rats injected 3.5 hours previously with the optimum teratogenic dose. (3) Rats were cultured for 24 out of 48 hours in serum from animals which had been injected with the optimum teratogenic dose 18.5 hours before bleeding. (4) Rats were cultured for 24 out of 48 hours in serum containing salicylate added to make up levels normally associated with (3). (5) A control culture was performed. The experiment indicates great similarity between the results obtained from animals cultured in serum with salicylate added and results from culture in serum of salicylate treated rats. It appears therefore that sodium salicylate - acting directly on the feto-placental unit - is the active teratogen rather than any of its metabolites.

Interaction of salicylates and other non-steroidal anti-inflammatory agents in rats as shown by gastro-ulcerogenic and anti-inflammatory activities, and plasma concentrations

The interaction of salicylates and other non-steroidal anti-inflammatory drugs was studied in rats. Concurrent oral administration of sodium salicylate (SS) or salicylic acid (SA) and indomethacin (IND) significantly reduced the gastro-ulcerogenicity and the plasma concentrations of IND. Acetylsalicylic acid (ASA) failed to do so. IND had no significant influence on plasma concentrations of SA. Simultaneous administration of SS and IND intraperitoneally or subcutaneously showed the same pattern of interaction as for oral administration. Concurrent oral administration of SS and IND exerted similar anti-inflammatory activity as the single drugs. SS significantly antagonized the ulcerogenicity of ibuprofen and tended to antagonize the ulcerogenic activity of ASA, phenylbutazone, tolfenamic acid and naproxen. The results suggest that in rats SS and SA (but not ASA) interact with IND concerning both gastro-ulcerogenicity and plasma concentrations of IND (but not of SA) and that the interaction is systemic in nature. We propose that the ulcerogenic interaction might be explained partly by the reduced IND plasma concentrations and partly by a weaker inhibition by SS of the prostaglandin system in the rat stomach.

Mass transfer characteristics of hollow-fiber dialyzers and hemoperfusion devices

Clearance versus time tests were carried out on three charcoal-based hemoperfusion devices (Sandev, Becton-Dickinson and Gambro) using solutions of 1 gm/L sodium salicylate in a pH 7.4 buffer and in bovine blood at flow rates of 200 ml/min. Similar tests were performed on a Cordis Dow 2.5 m2 hollow-fiber dialyzer at a tube side flow rate (QB) of 200 ml/min. Buffer was pumped through the dialysate side at a flow rate (QD) of 400 ml/min. Two dialyzers were run in series at QB = 200 ml/min and QD = 500 or 1000 ml/min. Mass transfer resistances were computed from the test results. These values are useful in that they constitute an index of the intrinsic initial kinetics of solute transfer in each device. However, the clearance versus time curves indicate that these initial kinetics decrease at different rates for each hemoperfusion unit as sorption capacity begins to be depleted. In contrast, the initial clearances for the dialyzers remain at their initial values. These data reveal much about the relative mass transfer characteristics of these devices.

Effects of sodium salicylate on plasma insulin concentration and fatty acid turnover in dogs

The effects of intravenous sodium salicylate administration on plasma concentrations of insulin, free fatty acids (FFA) and glucose were studied in intact, anaesthetized dogs both during basal and isoprenaline stimulated lipolysis. In both situations sodium salicylate reduced the plasma concentrations of insulin. The reduction was associated with decreased plasma FFA concentrations and FFA turnover rate, while plasma glucose concentrations remained unaltered. The reduced plasma insulin concentrations effected by sodium salicylate is most likely secondary to the concomitant fall in plasma FFA concentrations due to inhibition of FFA mobilization from adipose tissue.

Constant blood withdrawal method for area under plasma concentration-time curve

The area under the plasma concentration-time curve (AUC) was measured after an intravenous injection of sodium salicylate and after intragastric administration of aspirin, using either an intermittent sampling and the trapezoid rule (AUC-trapezoid) or the recently introduced constant blood withdrawal method (AUC-integrated concentration). Six dogs were used in each study. The AUC-integrated concentration was significantly higher than the AUC-trapezoid. The difference between the two methods was more significant after the intravenous infusion than after the intragastric administration. The higher AUC-integrated concentration was attributed to the inclusion of the initial plasma levels, which is an inherent advantage of the constant blood withdrawal method.

The distribution of salicylate in mouse tissues after intraperitoneal injection

The concentrations of salicylate and its principal metabolites were measured in blood, liver, brain, kidney, heart, spleen, diaphragm and skeletal muscle after the intraperitoneal injection of a fixed amount of radioactive salicylate and varying doses of unlabelled salicylate. The patterns of distribution of salicylate in the various organs with time were similar, the peak level being attained in 30–60 min after injection. Salicylate was eliminated from the blood after 8 hr but persisted in liver in measurable amounts up to 24 hr.