Pharmacokinetics and distribution of thiamphenicol in sheep given repeated intramuscular doses

The pharmacokinetics of thiamphenicol and its distribution in various body fluids were studied after repeated intramuscular injection in clinically healthy adult Moroccan crossed Sardi-D'Man sheep. Thiamphenicol was rapidly absorbed from injection sites yielding peak plasma concentrations within 15-30 min. The elimination from the blood was also rapid, with a biological half-life of 1.51 +/- 0.51 h. The distribution pattern of thiamphenicol revealed that this antibiotic can penetrate many remote sites of the body. With the exception of the cerebrospinal fluid, concentrations of the drug in other body fluids were higher than the corresponding plasma concentrations.     

Pharmacokinetics of delta9-tetrahydrocannabinol in dogs

The pharmacokinetics of intravenously administered 14C-delta9-tetrahydrocannabinol and derived radiolabeled metabolites were studied in three dogs at two doses each at 0.1 or 0.5 and 2.0 mg/kg. Two dogs were biliary cannulated; total bile was collected in one and sampled in the other. The time course for the fraction of the dose per milliliter of plasma was best fit by a sum of five exponentials, and there was no dose dependency. No drug was excreted unchanged. The mean apparent volume of distribution of the central compartment referenced to total drug concentration in the plasma was 1.31 +/- 0.07 liters, approximately the plasma volume, due to the high protein binding of 97%. The mean metabolic clearance of drug in the plasma was 124 +/- 3.8 ml/min, half of the hepatic plasma flow, but was 4131 +/- 690 ml/min referenced to unbound drug concentration in the plasma, 16.5 times the hepatic plasma flow, indicating that net metabolism of both bound and unbound drug occurs. Apparent parallel production of several metabolites occurred, but the pharmacokinetics of their appearance were undoubtedly due to their sequential production during liver passage. The apparent half-life of the metabolic process was 6.9 +/- 0.3 min. The terminal half-life of delta9-tetrahydrocannabinol in the pseudo-steady state after equilibration in an apparent overall volume of distribtuion of 2170 +/- 555 liters referenced to total plasma concentration was 8.2 +/- 0.23 days, based on the consistency of all pharmacokinetic data. The best estimate of the terminal half-life, based only on the 7000 min that plasma levels could be monitored with the existing analytical sensitivity, was 1.24 days. However, this value was inconsistent with the metabolite production and excretion of 40-45% of dose in feces, 14-16.5% in urine, and 55% in bile within 5 days when 24% of the dose was unmetabolized and in the tissue at that time. These data were consistent with an enterohepatic recirculation of 10-15% of the metabolites. Intravenously administered radiolabeled metabolites were totally and rapidly eliminated in both bile and urine; 88% of the dose in 300 min with an apparent overall volume of distribution of 6 liters. These facts supported the proposition that the return of delta9-tetrahydrocannabinol from tissue was the rate-determining process of drug elimination after initial fast distribution and metabolism and was inconsistent with the capability of enzyme induction to change the terminal half-life.     

Pharmacokinetics of ibutilide and its enantiomers in dogs

Signal transduction pathways activated by injury play a central role in coordinating the cellular responses that determine whether a cell survives or dies. GADD153 expression increases markedly in response to some types of cellular injury and the product of this gene causes cell cycle arrest. Using induction of GADD153 as a model, we have investigated the activation of the cellular injury response after treatment with taxol and cisplatin (cDDP). Activation of the GADD153 promoter coupled to the luciferase gene and transfected into human ovarian carcinoma 2008 cells correlated well with the increase in endogenous GADD153 mRNA after treatment with taxol but not after treatment with cDDP. Following treatment with cDDP, the increase in endogenous GADD153 mRNA was 10-fold greater than the increase in GADD153 promoter activity. Likewise, at equitoxic levels of exposure (IC80), cDDP produced a 5-fold greater increase in endogenous GADD153 mRNA than taxol. The tyrosine kinase inhibitor tyrophostin B46 had no significant effect on the ability of taxol to activate the GADD153 promoter, but inhibited activation of the GADD153 promoter by cDDP in a concentration-dependent manner. Tyrphostin B46 synergistically enhanced the cytotoxicity of cisplatin; however, the same exposure had no significant effect on the cytotoxicity of taxol. We conclude that (1) taxol and cDDP activate GADD153 promoter activity through different mechanisms; (2) the signal transduction pathway mediating induction by cDDP involves a tyrosine kinase inhibitable by tyrphostin B46; and (3) that inhibition of this signal transduction pathway by tyrphostin synergistically enhances cDDP toxicity.     

Pharmacokinetics of an injectable sustained-release formulation of morphine for use in dogs

This study investigated the pharmacokinetics of morphine sulphate in an injectable chitosan-based gel. Gels were made from a combination of N-O-carboxymethylchitosan (NOCC) and chitosan and were easily injectable via a 22 gauge needle and appeared stable during long-term storage. Groups of six beagles were injected subcutaneously (s.c.) with 1.2 mg/kg morphine sulphate, either in sterile saline or in sterilized gels, and serial blood samples were withdrawn via a jugular catheter and later analysed for morphine concentrations using radioimmunoassay. Data were analysed according to non-compartmental pharmacokinetics. NOCC-based gels resulted in significantly lower serum morphine concentrations at 10 and 30 min following injection but significantly higher concentrations at all points from 120 to 480 min post-injection. Dogs receiving morphine gel exhibited equivalent or lesser variability in serum morphine concentrations than dogs receiving conventional morphine sulphate. Pharmacokinetic analysis revealed that morphine release from the gel matrix was significantly prolonged but fully bioavailable. There were no significant differences in either distribution (Vd) or terminal elimination (t 1/2). Dogs experienced no adverse effects other than those normally associated with morphine administration at the time of injection but all dogs receiving the gel presented with an undefined stiffness the next day that resolved spontaneously within 48 h. We conclude that carboxymethylchitosan-based gels hold considerable promise for the development of injectable sustained-release formulations of opioid analgesics.     

Pharmacokinetics of liposome-encapsulated meglumine antimonate after intramuscular and subcutaneous administration in dogs

We describe a transient figurate erythema in an 11-month-old female infant with a 2-month history of arcuate and annular erythematous lesions localized on the face, trunk, and limbs. Constitutional symptoms were absent. Previous medical history was unremarkable. Full blood examination, erythrocyte sedimentation rate, antistreptolysin-O titer, anti-Ro, and anti-La antibodies were within normal limits or negative. Histologic examination revealed a superficial and deep perivascular and interstitial dermatitis constituted mostly of neutrophils and abundant nuclear dust. The lesions resolved spontaneously within a few months without scarring or atrophy. Recurrence has not occurred. This case suggests that figurate erythemas in infants rarely may disclose a neutrophilic histologic pattern, which must be differentiated from that of other neutrophilic dermatoses.     

Pharmacokinetics and pharmacodynamics of mivacurium stereoisomers in beagle dogs using twitch height and train-of-four response

Mivacurium, a non-depolarizing neuromuscular blocking agent, consists of three isomers; trans-trans (57%), cis-trans (36%) and cis-cis (7%). The purpose of this study was to characterize the pharmacokinetics and pharmacodynamics of mivacurium after various inputs. Four beagle dogs weighing between 7.95 and 9.89 kg were anesthetized with isofluorane (5%) and received a bolus dose (0.010-0.020 mg kg(-1)) and two constant rate infusions (1.0-1.5 microg kg(-1) min(-1)) of mivacurium via the saphenous vein. Single twitch height (TH) and train-of-four (TOF) were evaluated every 15 and 30 s, respectively. Arterial blood samples were collected, processed and analysed for mivacurium using a stereospecific HPLC-fluorescence method. The disposition of mivacurium isomers was best described by a two compartment model. Mean Cl for the cis-trans, trans-trans and cis-cis isomers were 19.98, 13.53 and 3.47 mL min(-1) kg(-1) respectively and the corresponding mean Vdss were 0.29, 0.24 and 1.00 L kg(-1). The measurement of onset showed dose dependence as evidenced by a rapid onset at the higher doses. TOF measurements were more sensitive to the onset of action and required a longer period of time to recover to baseline values as compared with TH measurements.     

Pharmacokinetics of the new antiasthma and antiallergy drug, azelastine, in pediatric and adult beagle dogs

The plasma concentrations and relative bioavailability of azelastine hydrochloride (AZ) and its desmethyl metabolite (DAZ) after a single and 10 once-a-day oral doses of 2.5 mg kg-1 AZ were determined in adult male and female and pediatric male and female beagle dogs. The pediatric and adult dogs were 4-6 weeks and 1-2 years of age, respectively. An analysis of variance (ANOVA) was performed on the bioavailability parameters among all groups and between the first and last doses. No statistically significant (p < 0.05) sex-related differences in the bioavailability parameters were observed. The peak concentration (Cmax) of AZ, especially after the first dose, was significantly higher in pediatric dogs than that in adult dogs, whereas following the multiple AZ administrations, the bioavailability parameters for the last dose were similar in the two age groups. The apparent volume of distribution (Vss) of AZ suggested that the drug was extensively distributed into tissue in adult as well as in pediatric dogs. The Vss was considerably smaller in pediatric dogs, which may explain the higher Cmax in this age group. The bioavailability of the metabolite in adult dogs after multiple administration of AZ was higher than that in pediatric dogs. Although some differences in the parameters among the groups are statistically significant, they do not appear to have any biological significance. Therefore, similar AZ dosages may be required in pediatric and in adult populations to achieve optimum therapeutic drug levels.     

Pharmacokinetics of succinylcholine in man

The aim of this study was to compare endocrine changes and the follicular development in patients receiving pure FSH alone or in association with LH after desensitization with an LH-RH agonist depot. Thirty four cycles were selected for this prospective randomized study. Desensitization was obtained using Goserelin the cycle before the stimulation. Induction of ovulation for IUI was carried out with 225 IU/day of pure FSH or with 225 IU/day of hMG. The number of days and ampules required for follicular maturation were equivalent in the two groups. The same number of follicles were developed, while different, but not significant, pregnancy rates were obtained. Estradiol values at the end of stimulation were significantly lower for FSH group. In conclusion the contemporary administration of LH with FSH does not exert any effect on follicular development, but it seems to facilitate E2 synthesis, probably providing more substrate for the aromatization process.     

Pharmacokinetics of phenolsulfonphthalein in sheep

Pharmacokinetic variables of phenolsulfonphthalein (PSP) were determined in sheep after rapid IV injection and IV infusion to steady state. In Suffolk wethers, an average of < 75% of an IV administered dose was eliminated in urine, indicating that measures of systemic clearance overestimate renal clearance in this species. Furthermore, PSP elimination from plasma was more rapid in Suffolk than Rambouillet wethers and, in Suffolk ewes, systemic clearance decreased from mean +/- SD 7.8 +/- 0.3 ml/min/kg of body weight to 4.7 +/- 1.1 ml/min/kg at steady-state plasma concentration of 2.4 +/- 0.3 and 151.3 +/- 31.8 micrograms/ml, respectively. These observations indicate that, similar to that in other species, systemic clearance of PSP in sheep is concentration-dependent and that significant differences may exist between breeds.     

Pharmacokinetics of indoramin in man

Bacterial luciferase from Photobacterium phosohoreum was found to produce bioluminescence on reaction with FMN and H2O2 in the presence of aldehyde. This luminescence is presumably produced by the same X1 intermediate as that found in FMNH2-O2 initiated luminescence. From the ratio of the light intensities of the FMN-H2O2 initiated reactions, we calculated the association constant of the reaction, luciferase+FMN+H2O2in equilibriumX1, and estimated its temperature dependence. From these results we calculated the thermodynamic parameters of the reaction, luciferase+FMNH2+O2in equilibriumX1. We found that the free energy level of X1 is only 3.2 kcal below that of fr-e FMN and H2O2. We also estimated the thermodynamic parameters of other steps of the luminescent reaction. The values obtained showed that the formation of X1 from luciferase, FMNH2 and O2 involves a positive entropy change, but the intermediate is in a state stabilized against decomposition. Results also suggest a considerable degree of electronic rearrangement on formation of the excited-state molecule from the X1-aldehyde complex.     

Pharmacokinetics of rapamycin

Based on the present findings, a number of preliminary conclusions can be made regarding the distribution, pharmacokinetics, and therapeutic range investigations with RAPA: (a) the majority of the drug is sequestered in erythrocytes, resulting in whole blood concentrations; (b) the drug has a relatively long half-life in both humans and animals with 24-hour trough concentrations being within the analytical range of HPLC when immunosuppressive doses are administered; (c) the drug exhibits a proportionality between trough concentrations and dose; (d) trough concentrations of the drug appear to be related to immunosuppressive efficacy and drug-related side effects. The studies described here should provide a basis for the establishment of therapeutic monitoring protocols for RAPA.     

Pharmacokinetics of ipriflavone

Ipriflavone administered to rats orally is well absorbed from small intestine via the portal route, distributed widely in tissues, metabolized extensively by oxidation, and eliminated from the body preferentially in urine. The absorption of ipriflavone is less effective in dogs, than in rats. In dogs, the compound absorbed is metabolized in the same way as in rats and the metabolites formed are eliminated largely in faeces, together with unabsorbed ipriflavone. In human, ipriflavone administered orally is rapidly absorbed, and quickly metabolized. The dose is eliminated mainly via the urinary route as metabolites (57% of the dose), and the smaller fraction with the faeces, mostly as ipriflavone (40% of the dose). There is no significant change in the pharmacokinetics of ipriflavone even after multiple dose. In the serum, ipriflavone and its metabolites are primarily bound to albumin, the binding is 94-99% and totally reversible.     

Pharmacokinetics of the penicillins in man

The purpose of this article is to review and summarise those aspects of the pharmacokinetic behaviour of the penicillins that may be of particular interest to the clinician. While these antibiotics differ markedly in their acid stability and oral absorption, misleading inferences may be drawn from simple inspection of the maximal serum concentrations produced by a given dose administered orally. A more accurate picture emerges when serum protein binding and intrinsic activity of the drugs are taken into account. All of the penicillins are readily and actively secreted by the renal tubles and most are eliminated, almost completely unchanged, in the urine. The majority are excreted in small quantities in the bile, but this is a major route for elimination of nafcillin from the body. Distribution of the penicillins in 'non-specialised' sites is excellent. In contrast, penetration of the central nevous system and eye are poor, and of the prostate, minimal. Inflammation reduces the barries to penetration of these areas. However, quantitative data related to this phenomenon in man are few. Probenecid actively competes with the 'export' pump of the meninges and renal tubular cells. This results in an increase in concentrations of the penicillins in the blood and cerebrospinal fluid. The effect of this agent on active secretion of these antibiotics from the eye and biliary tract is minimal. While elimination of the penicillins from the body takes place largely via renal excretion, penicillin V and oxacillin are extensively degraded as well. In contrast to the situation with respect to 'natural' and 'broad-spectrum' penicillins, the serum half-life of the isoxazolyl congeners and nafcillin is only minimally prolonged in the presence of renal failure. These agents are only weakly haemodialyzable, while the other penicillins are rapidly removed from the circulation by this procedure.     

Pharmacokinetics of moricizine in young patients

Moricizine is a novel phenothiazine antiarrhythmic agent that depresses the activity of ectopic foci, has a low incidence of adverse effects relative to other agents, and is useful in treating pediatric atrial ectopic tachycardia. A study was conducted to determine the pharmacokinetics of moricizine in children after oral administration. Moricizine was isolated from frozen serum obtained from four male patients (ages 7, 8, 9, and 18 years) receiving the drug for supraventricular tachycardia and analyzed by high-performance liquid chromatography with ultraviolet detection according to an established protocol. Peak serum levels were between 400 and 2000 ng/mL. Elimination of moricizine did not follow simple single-compartment pharmacokinetics. In three patients we observed an increase or slower decline in blood level occurring after 4 hours. Because of the paroxysmal nature of the tachycardias, decreases in patient heart rate could not be correlated with moricizine blood level. These results suggest that the pediatric pharmacokinetics of moricizine excretion are complex and may differ from those seen in adults.     

Pharmacokinetics of acyclovir in the cat

To investigate the detoxification of bromobenzene-induced hepatic lipid peroxidation by Oenanthe javanica DC, the hepatic lipid peroxide level and the activities of enzymes responsible for production and removal of epoxide were studied. The level of lipid peroxide elevated by bromobenzene was significantly reduced by the methanol extract (250 mg/kg) and persicarin (5 mg/kg). The methanol extract and persicarin administered daily over 4 weeks before intoxication with bromobenzene did not affect the activities of aminopyrine N-demethylase, aniline hydroxylase, and glutathione S-transferase. Epoxide hydrolase activity was decreased significantly by bromobenzene, which was restored to the control level by pretreatment with persicarin. However, the identical pretreatment with isorhamnetin and hyperoside did not change the enzyme activity or lipid peroxide level. The results suggest that the reduction of bromobenzene-induced hepatic lipid peroxidation by O. javanica under our experimental conditions is effected through enhancing the activity of epoxide hydrolase, an enzyme removing bromobenzene epoxide. In addition, the bioactive component of this plant responsible for the detoxification of bromobenzene, at least in part, is thought to be persicarin.     

Pharmacokinetics of mexiletine in renal insufficiency

Mexiletine (Mexitil) is an effective antiarrhythmic drug for the treatment of ventricular dysrhythmias. The therapeutic plasma level is situated between 0.75 and 2 microgram/ml. For concentrations higher than 2 microgram/ml, the percentage of severe side effects is rapidly increasing without improvement of the therapeutic efficacy. The main pharmacokinetics parameters of mexiletine are reviewed in the first part of this publication. Contrary to lidocaine, mexiletine may be administrated orally (or intravenously). It is largely and rapidly distributed in the body. The apparent volume of distribution (Vd) is greater than 500 1. The plasma half-time is 10 to 12 hours in healthy volunteers with a 70% plasma protein fixation. Mexiletine is largely metabolized to conjugates after N-methylation and hydroxylation. In the second part of the work, the influence of renal insufficiency on the plasma half-time of mexiletine has been investigated in 11 patients presenting a creatinine clearance situated between 2 and 38 ml/min. The mean plasma half-time for these patients is 11.1 +/- 1.7 hours after a single i.v. injection of 1.5 mg/kg. This value is comparable to the normal values found in the literature. Our control group containing convalescents from acute myocardial infarct has a plasma half-time of only 5.9 hours. In conclusion, the renal insufficiency has not modified the plasma elimination half-time of mexiletine after a single i.v. injection.     

Pharmacokinetics of intravenous omeprazole in children

This study was undertaken to define the pharmacokinetics of omeprazole in children and included 13 patients, heterogeneous in terms of age (0.3 to 19 years), underlying disease and biological constants, indication of omeprazole administration and associated therapy. The dose administered ranged from 36.9 to 139 mg.1.73 m-2. The pharmacokinetic parameters of omeprazole were: systemic clearance, 0.23 l.kg-1.h-1; volume of distribution, 0.45 l.kg-1; elimination half life 0.86 h; but were highly variable between individuals. Dosage, differences in hepatic and renal function and associated therapy may contribute to inter-individual variability. Within the range of doses administered, the pharmacokinetic parameters were similar to those reported in adults. The drug has been well tolerated in all children.     

Pharmacokinetics and disposition of triptonide in rats

Triptonide, isolated from Tripterygium wilfordii Hook., was found to show significant antiinflammatory, immunosuppression and antitumor activities. A RP-HPLC method was applied to determine the plasma concentration of triptonide at different times in rats. Concentration-time curves after i.v., 0.7, 1.4 and 2.8 mg.kg-1 of triptonide were fitted to a two-compartment open model with T1/2 alpha of 0.167-0.195 h and T1/2 beta of 4.95-6.49 h. The area under curves (AUCs) were linearly related to the dosages (gamma = 0.9894). Systematic clearances (CLs) were independent of dosages. Mean residence time (MRT) of the three doses was 3.26-5.14 h by noncompartmental (the statistical moment method) analyses. The tissue distribution of triptonide in rats appeared to be wide throughout the body. The triptonide levels were high in the lung and liver, moderate in the heart, kidney, spleen and muscle and low in the testis, intestine and brain. Data of the urine and bile excretion indicated that only a small percent of unchanged triptonide was excreted. Plasma protein binding of triptonide rate was about 75%.