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M Tod

Publications and source records attributed to M Tod.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cefepime and amikacin synergy in vitro and in vivo against a ceftazidime-resistant strain of Enterobacter cloacae.

The activities of cefepime and amikacin alone or in combination against an isogenic pair of Enterobacter cloacae strains (wild type and stably derepressed, ceftazidime-resistant mutant) were compared using an experimental model of pneumonia in non-leucopenic rats. Animals were infected by administering 8.4 log10 cfu of E. cloacae intratracheally, and therapy was initiated 12 h later. At that time, the animals' lungs showed bilateral pneumonia and contained more than 7 log10 E. cloacae cfu/g tissue. Because rats eliminate amikacin and cefepime much more rapidly than humans, renal impairment was induced in all animals to simulate the pharmacokinetic parameters of humans. In-vitro susceptibilities showed an inoculum effect with cefepime proportional to the bacterial titre against the two strains, but more pronounced with the stably derepressed mutant strain, whereas with bacterial concentrations of up to 7 log10 cfu/mL, no inoculum effect was observed with amikacin. In-vitro killing indicated that antibiotic combinations were synergic only at intermediate concentrations. At peak concentrations, the combination was merely as effective as amikacin alone. At trough concentrations, a non-significant trend towards the superiority of the combination over each antibiotic alone was noted. Moreover, cefepime was either bacteriostatic or permitted regrowth of the organisms in the range of antibiotic concentrations tested. Although each antibiotic alone failed to decrease bacterial counts in the lungs, regardless of the susceptibility of the strain used, the combination of both antibiotics was synergic and induced a significant decrease in the lung bacterial count 24 h after starting therapy when compared with tissue bacterial numbers in untreated animals or animals treated with either antibiotic alone. No resistant clones emerged during treatment with any of the antibiotic regimens studied.

Amikacin↗
PubMed1998

Influence of renal failure on ciprofloxacin pharmacokinetics in rats.

Ciprofloxacin pharmacokinetics have been shown to be modified in patients with renal failure (e.g., the intestinal secretion of ciprofloxacin is increased). This study investigated the influence of renal failure on the pharmacokinetics of ciprofloxacin following oral and parenteral administration to rats of a dose of 50 mg/kg of body weight. After parenteral administration, only renal clearance (CLR) was reduced in nephrectomized rats (5.3+/-1.4 versus 17.8+/-4.7 ml/min/kg, P < 0.01, nephrectomized versus control rats). However, nonrenal clearance was increased in nephrectomized rats (32+/-4 versus 15+/-5 ml/min/kg, P < 0.01, nephrectomized versus control rats), suggesting compensatory mechanisms for reduced renal function. After oral administration, apparent total clearance and CLR were reduced (P < 0.01) in nephrectomized rats (117+/-25 and 6.8+/-4.4 ml/min/kg, respectively) compared with the values for control rats (185+/-9 and 22.6+/-5.3 ml/min/kg, respectively) and the area under the concentration-time curve was higher (P < 0.01) for nephrectomized rats (436.3+/-90.5 mg. min/liter) than for control rats (271.3+/-14.3 mg.min/liter). Terminal elimination half lives in the two groups remained constant after oral and parenteral administration. These results suggest an increased bioavailability of ciprofloxacin in nephrectomized rats, which was confirmed by a nonlinear mixed-effect model.

Administration, Oral↗
PubMed1998

Population pharmacokinetic study of amikacin administered once or twice daily to febrile, severely neutropenic adults.

Once-daily (o.d.) administration of 20 mg of amikacin per kg of body weight to neutropenic patients has been validated by clinical studies, but amikacin pharmacokinetics have been documented only for the 7.5-mg/kg twice-daily (b.i.d.) regimen in this population. In order to determine in neutropenic patients (i) the influence of the dosing regimen on the kinetics of amikacin, (ii) the linearity of kinetics of amikacin in the range of 7.5 to 20 mg/kg, and (iii) the influence of patient characteristics on the disposition of amikacin and (iv) to provide a rationale for dosing recommendations, we evaluated the population pharmacokinetics of amikacin administered to 57 febrile neutropenic adults (neutrophil count, <500/mm3) being treated for a hematological disorder and receiving amikacin at 7.5 mg/kg b.i.d. (n = 29) or 20 mg/kg o.d. (n = 28) and administered intravenously over 0.5 h. A total of 278 blood samples were obtained (1 to 14 samples per patient) during one or several administration intervals (1 to 47). Serum amikacin levels were measured by the enzyme-multiplied immunoassay technique. A mixed-effect modeling approach was used to fit a bicompartmental model to the data (NONMEM software). The influences of the dosing regimen and the demographic and biological indices on the pharmacokinetic parameters of amikacin were evaluated by the maximum-likelihood ratio test on the population model. The dosing regimen had no influence on amikacin pharmacokinetic parameters, i.e., the kinetics of amikacin were linear over the range of 7.5 to 20 mg/kg. Amikacin elimination clearance (CL) was only correlated with creatinine clearance or its covariates, namely, sex, age, body weight, and serum creatinine level. The interindividual variability of CL was 21%, while those of the central volume of distribution, the distribution clearance, and the tissue volume of distribution were 15, 30, and 25%, respectively. On the basis of the expected distribution of amikacin concentrations in this population, dosing recommendations as a function of creatinine clearance (CL[CR]) are proposed: for patients with normal renal function (CL[CR] of 80 to 130 ml/min), 20 mg/kg o.d. is recommended, whereas for patients with severe renal impairment (CL[CR], 10 to 20 ml/min), a dosage of 17 mg/kg every 48 h is recommended.

Adolescent↗
PubMed1998

Analysis of the pharmacokinetic interaction between cephalexin and quinapril by a nonlinear mixed-effect model.

Oligopeptidic drugs such as beta-lactams and angiotensin-converting enzyme inhibitors share the same carriers in humans and animals, which results in possible pharmacokinetic interactions. To model such interactions, the effects of quinapril on cephalexin pharmacokinetics were investigated in rats. Blood cephalexin concentrations were measured by liquid chromatography, and the data were analyzed by a noncompartmental method and by fitting a bicompartmental model by a nonlinear mixed-effect modeling approach. Five groups of eight rats were examined. In the first three groups, cephalexin elimination kinetics after intra-arterial administration alone or in combination with quinapril given by the parenteral or the oral route were studied, and the occurrence of a pharmacokinetic interaction was not revealed. The absence of an effect of quinapril on cephalexin elimination after parenteral administration might be explained either by the higher affinity of cephalexin for the renal anionic transport system than that of quinapril or by the much higher concentrations of cephalexin than those of quinapril. In the last two groups, cephalexin was administered by the oral route alone or in combination with quinapril. The mean area under the concentration-time curve (AUC) for cephalexin was increased by ca. 30% by coadministration of quinapril (40.1 versus 31.4 mg.h/liter; P = 0.04). The mean elimination clearance of cephalexin was significantly decreased by quinapril, from 0.81 to 0.64 liter/h/kg of body weight (P < 0.05), probably by competitive inhibition of cephalexin secretion at the tubular level. The mean absorption rate constant of cephalexin was significantly lowered by quinapril (from 0.249 to 0.177 h-1; P < 0.01), without modification of the extent of absorption (89%). This pharmacokinetic interaction could be explained by competitive inhibition of cephalexin active transport by quinapril at the intestinal level.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Clinical pharmacokinetics of diacerein.

Diacerein is a drug for the treatment of patients with osteoarthritis. This drug is administered orally as 50 mg twice daily. Diacerein is entirely converted into rhein before reaching the systemic circulation. Rhein itself is either eliminated by the renal route (20%) or conjugated in the liver to rhein glucuronide (60%) and rhein sulfate (20%); these metabolites are mainly eliminated by the kidney. The pharmacokinetics characteristics of diacerein are about the same in young healthy volunteers and elderly people with normal renal function, both after a single dose (50 mg) or repeated doses (25 to 75 mg twice daily). Rhein kinetics after single oral doses of diacerein are linear in the range 50 to 200 mg. However, rhein kinetics are time-dependent, since the nonrenal clearance decreases with repeated doses. This results in a moderate increase in maximum plasma concentration, area under the plasma concentration-time curve and elimination half-life. Nevertheless, the steady-state is reached by the third administration and the mean elimination half-life is then around 7 to 8 hours. Taking diacerein with a standard meal delays systemic absorption, but is associated with a 25% increase in the amount absorbed. Mild-to-severe (Child Pugh's grade B to C) liver cirrhosis does not change the kinetics of diacerein, whereas mild-to-severe renal insufficiency (creatinine clearance < 2.4 L/h) is followed by accumulation of rhein which justifies a 50% reduction of the standard daily dosage. Rhein is highly bound to plasma proteins (about 99%), but this binding is not saturable so that no drug interactions are likely to occur, in contrast to those widely reported with nonsteroidal anti-inflammatory drugs. Except for moderate and transient digestive disturbances (soft stools, diarrhoea), diacerein is well tolerated and seems neither responsible for gastrointestinal bleeding nor for renal, liver or haematological toxicity.

Aged↗
PubMed1997

Comparison of ED, EID, and API criteria for the robust optimization of sampling times in pharmacokinetics.

Optimization of the sampling schedule can be used in pharmacokinetic (PK) experiments to increase the accuracy and the precision of parameter estimation or to reduce the number of samples required. Several optimization criteria that formally incorporate prior parameter uncertainty have been proposed earlier. These criteria consist in finding the sampling schedule that maximizes the expectation (over a given parameter distribution) of det F (ED-optimality) or Log(det F) (API-optimality), or minimizes the expectation of 1/det F (EID-optimality), where F is the Fisher information matrix. The precision and the accuracy of parameter estimation after having fitted a PK model to a small number of optimal data points (determined according to D, ED, EID, and API criteria) or to a naive sampling schedule were compared in a Monte Carlo simulation study. A one-compartment model with first-order absorption rate (3 parameters) and a two-compartment model with zero-order infusion rate (4 parameters) were considered. Data were simulated for 300 subjects with both structural models, combined with several residual error models (homoscedastic, heteroscedastic with constant or variable coefficient of variation). Interindividual variabilities in PK parameters ranged from 25-66%. ED-, EID-, and API-optimal sampling times were calculated using the software OSP-Fit. Three or five samples were allowed for parameter estimation by extended least-squares. Performances of each design criterion were evaluated in terms of mean prediction error, root mean squared error, and number of acceptable estimates (i.e., with a SE less than 30%). Compared to the D-optimal design, the EID and API designs reduced the bias and the imprecision of the estimation of the parameters having a large interindividual variability. Moreover, the API design resulted in some cases in a higher number of acceptable estimates.

Models, Biological↗
PubMed1997

Implementation and evaluation of a stochastic control strategy for individualizing teicoplanin dosage regimen.

A stochastic control strategy for individualizing teicoplanin dosing schedule in neutropenic patients is proposed and compared to the usual Bayesian approach based on the mode of the posterior density of the model parameters. Teicoplanin disposition is described by a bicompartmental model. Age, body weight, serum creatinine, white blood cell count, and sex can be included as covariates. Posterior density of model parameters is obtained by Bayes theorem under a discrete form from which the posterior density of teicoplanin trough concentrations are computed for any dosing schedule. Optimal maintenance dose is determined by minimizing the cost associated, through a logarithmic risk function, to the concentrations being outside the therapeutic range. In Monte Carlo simulation studies on 300 individuals, stochastic control was more accurate than, and equally precise as the usual Bayesian approach. Two-sample based predictions were not better than one-sample based ones. Inclusion of covariates in the model improved dramatically the performances of both strategies. A small retrospective study based on real data (n = 16 patients) shows that reasonable accuracy (bias of 0.7 mg/L) and precision (3 mg/L) in teicoplanin trough concentration prediction is obtained with both strategies provided that covariates are taken into account.

Age Factors↗
PubMed1997

Cefepime and amikacin synergy against a cefotaxime-susceptible strain of Enterobacter cloacae in vitro and in vivo.

We developed an experimental model of pneumonia to evaluate the efficacy of new antibiotic regimens against Enterobacter cloacae. Rats were infected by administering 8.5 log10 cfu E. cloacae intratracheally, and therapy was initiated 24 h later. At that time, animals' lungs showed bilateral pneumonia containing more than 7 log10 cfu/g of tissue. Because rats eliminate amikacin and cefepime much more rapidly than humans, renal impairment was induced in all animals to simulate the pharmacokinetic parameters in humans. Using this model, we compared the bactericidal activities of cefepime and amikacin alone or in combination against the same cefotaxime-susceptible E. cloacae strain. The MICs of cefepime and amikacin for this strain were 0.5 and 2 mg/L, respectively. In-vitro killing studies showed that antibiotic combinations were synergic only at intermediate concentrations. At peak concentrations, the combination was only as effective as amikacin alone. At trough concentrations, a non-significant trend towards the superiority of the combination over cefepime alone was found. In-vivo studies showed that each antibiotic alone failed to decrease bacterial counts in the lungs except at 6 h, whereas the combination of both antibiotics induced a significant decrease in the lung bacterial count 6, 12 and 24 h after the onset of therapy when compared with tissue bacterial numbers in untreated animals or animals treated with either antibiotic alone. In-vivo synergy between cefepime and amikacin was observed at the three time points studied. No resistant clones emerged during treatment with any of the antibiotic regimens studied.

Amikacin↗
PubMed1996

Implementation of OSPOP, an algorithm for the estimation of optimal sampling times in pharmacokinetics by the ED, EID and API criteria.

The most common approach to optimize the sampling schedule in parameter estimation experiments is the D-optimality criterion, which consists in maximizing the determinant of the Fisher information matrix (max det F). In order to incorporate prior parameter uncertainty in the optimal design, other criteria have been proposed: The ED = max E (det F), EID = min E (l/det F) and API = max E (log det F) criteria, where the expectation is with respect to the given prior distribution of the parameters. Previously described algorithm for the estimation of optimal sampling times according to these criteria are adaptive random search (ARS), a robust and global but slow optimizer for API, and stochastic gradient (SG), a fast but local optimizer for ED and EID. We implemented an algorithm named OSPOP 1.0, based on non-adaptive random search (RS) followed by stochastic gradient to determine optimal sampling times for parameter estimation in various pharmacokinetic models according to ED, EID and API criteria. Prior distributions are allowed to be uniform, normal or lognormal. This algorithm combines the robustness of RS and the speediness of SG (convergence is obtained in a few minutes on a microcomputer). The results of the SG algorithm have been compared to those described in the literature using the ARS algorithm on a one compartment model with first- order absorption and were very similar. Also, the CPU time needed by SG and ARS algorithms were compared and the former proved to be much faster. Then, it has been applied to a five parameters stochastic model with zero-order absorption rate and Weibull-distributed residence times which was shown to describe adequately the kinetics of metacycline in humans. Population pharmacokinetic parameters of metacycline were estimated from a six subject pilot study, by the iterative two-staged method, using ADAPT II repeatedly. Optimal sampling times were determined with each criterion (ED, EID, API) with a multivariate normal prior parameter distribution. Six to seven distinct sampling times could be estimated. Higher numbers of samples revealed coalescing of design points.

Algorithms↗
PubMed1996

Monitoring of 8-methoxypsoralen during extracorporeal photochemotherapy: evidence for a "first-dose" effect.

Therapeutic monitoring of 8-methoxypsoralen (8-MOP) was studied in 12 patients (age range 43-85 years, weight range 48-76 kg) treated for Sezary's syndrome by extracorporeal photochemotherapy (ECP) for 14-41 months. Before the beginning of each ECP cycle (2 sessions on consecutive days at about 4-week intervals), a blood sample was drawn to determine the 8-MOP plasma concentration 2 h after drug ingestion. Plasma 8-MOP levels were measured using a high-performance liquid chromatography method with spectrophotometric detection. Monitoring parameters (dose, 2-h plasma 8-MOP concentration) showed important interindividual and intraindividual variations. The 8-MOP dose ranged from 0.57 to 1.04 mg/kg. Intraindividual variations of 2-h 8-MOP levels ranged from 21% to 75%. Of the 652 measurements, 13% were < 100 ng/ml, the therapeutic threshold for effective ECP; in three of the seven patients, increasing the dose obtained levels exceeding the therapeutic threshold, i.e, the absorption was not saturable. Orthogonal regression analysis between plasma 8-MOP concentrations measured in two consecutive ECP sessions showed a first-dose effect: the 2-h plasma 8-MOP concentration was significantly lower after the first administration than after the second (approximately 1.26-fold). Because 8-MOP has been proven to be a potent suicide inhibitor of drug metabolism in rats and humans, it is possible that 8-MOP had an inhibitory effect on its own metabolism within the therapeutic dose range for ECP, which would explain in part the inter- and intraindividual variability in 8-MOP kinetics and first-dose effect.

Adult↗
PubMed1996

Influence of experimental rat model of multiple organ dysfunction on cefepime and amikacin pharmacokinetics.

We adapted an experimental model of multiple organ dysfunction to study the alterations it induces in the pharmacology of cefepime and amikacin. The half-lives of both antibiotics were significantly prolonged because of nonsignificant enhancement of the volume of distribution and reduced renal elimination. In the presence of multiple organ dysfunction, the concentration of each antibiotic in the lungs, compared with that in the lungs of healthy controls, was significantly decreased, despite similar concentrations in plasma, indicating that the application of a standard antibiotic concentration in plasma could lead to underdosage in tissues during the initial days of therapy.

Amikacin↗
PubMed1996

Pharmacokinetic interaction between cefdinir and two angiotensin-converting enzyme inhibitors in rats.

The pharmacokinetic interaction between cefdinir and an angiotensin-converting enzyme inhibitor (captopril or quinapril) was investigated in rats. The linearity of cefdinir pharmacokinetics was demonstrated in three groups of rats receiving 10, 20, or 40 mg of cefdinir per kg of body weight intravenously. Then, three other groups of rats were established as follows: group 1 (n = 5) received cefdinir (10 mg/kg) intravenously, and 12 blood samples per rat were drawn between 0 and 8 h after injection of the dose; group 2 (n = 5) was treated in the same way as group 1, but captopril (0.8 mg/kg) was coadministered by intraintestinal injection into all animals; group 3 (n = 6) was treated in the same way as group 2, but quinapril (0.8 mg/kg) replaced captopril. Plasma cefdinir concentrations were measured by liquid chromatography, and the data were analyzed by a noncompartmental method. Finally, three groups of four or five rats each were set up as described above, but the cefdinir dose was 20 mg/kg and the animals were sacrificed 1 h after drug injection to collect blood to determine the unbound cefdinir fraction (fu) by ultrafiltration. The angiotensin-converting enzyme inhibitors increased the mean cefdinir area under the concentration-time curve up to 8 h by a factor of 1.8 (captopril; P < 0.05) and a factor of 3.5 (quinapril; P < 0.05). With captopril, mean cefdinir clearance was decreased by a factor of 2, and the volume of distribution increased by the same factor, while the fu increased from 15.4% +/- 3.0% (cefdinir alone) to 22.8% +/- 10.9% (cefdinir plus captopril). Captopril increased the cefdinir half-life from 0.62 +/- 0.17 to 2.92 +/- 0.95 h. With quinapril, the interaction was so strong that no elimination phase was detectable in four of the six rats, and therefore, no pharmacokinetic parameter values other than the cefdinir fu could be calculated; the cefdinir fu increased to 25.1% +/- 11.1%. It is concluded that captopril and quinapril (and/or their metabolites) have a major impact on the disposition of cefdinir in rats, probably by competition at the plasma protein-binding level and at the tubular anionic carrier level. This latter mechanism should also be relevant in humans.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Population pharmacokinetic study of isepamicin with intensive care unit patients.

The pharmacokinetics (PK) of isepamicin, a new aminoglycoside, were studied in 85 intensive care unit (ICU) patients and were compared with those observed in 10 healthy volunteers. A parametric method based on a nonlinear mixed-effect model was used to assess population PK. Isepamicin was given intravenously over 0.5 h at dosages of 15 mg/kg once daily or 7.5 mg/kg twice daily. The data were fitted to a bicompartmental open model. Compared with healthy volunteers, the mean values of the PK parameters were profoundly modified in ICU patients: elimination clearance was reduced by 48%, the volume of distribution in the central compartment (Vc) was increased by 50%, the peripheral volume of distribution was 70% higher, the distribution clearance was 146% lower, and the elimination half-life was ca. 3.4 times higher. The interindividual variability in PK parameters was about 50% in ICU patients. Five covariates (body weight [BW], simplified acute physiology score [SAPS], temperature, serum creatinine level, and creatinine clearance [CLCR]) were tentatively correlated with PK parameters by multivariate linear regression analysis with stepwise addition and deletion. The variability of isepamicin clearance was explained by three covariates (BW, SAPS, and CLCR), that of Vc was explained by BW and SAPS, and that of the elimination half-life was explained by CLCR and SAPS. Simulation of the concentration-versus-time profile for 500 individuals showed that the mean peak (0.75 h) concentration was 18% lower in ICU patients than in healthy volunteers and that the range in ICU patients was very broad (28.4 to 95.4 mg/liter). Therefore, monitoring of the isepamicin concentration is in ICU patients is mandatory.

Adult↗
PubMed1996

Population pharmacokinetic study of teicoplanin in severely neutropenic patients.

The teicoplanin pharmacokinetics (PK) of 30 febrile and severely neutropenic patients (polymorphonuclear count, < 500/mm3) with hematologic malignancies were compared with those determined for five healthy volunteers (HV). Neutropenic patients were given piperacillin combined with amikacin, and teicoplanin was added to the regimen the day fever developed in patients suspected of having a staphylococcal infection or 48 h later. Teicoplanin was given intravenously at a dosage of 6 mg/kg of body weight at 0, 12, and 24 h and once a day thereafter. Five to eleven blood samples per patient were collected. Teicoplanin concentrations were measured by liquid chromatography. A bicompartmental model was fitted to the data by a nonlinear mixed-effect-model approach. Multiple-linear regression analysis was applied in an attempt to correlate PK parameters to nine covariates. The mean trough concentrations of teicoplanin 48 h after the onset of treatment and 24 h after the last injection (last trough) +/- standard deviations were 8.8 +/- 4.1 and 17.5 +/- 13.5 mg/liter, respectively. A significant increase was noted in the mean rate of elimination clearance of teicoplanin in neutropenic patients compared with that of HV (0.86 versus 0.73 liter/h, P = 0.002), as was the case with rates of distribution clearance (5.89 versus 4.94 liter/h, P = 0.002); the mean half-life of distribution was significantly shorter in patients than in HV (0.43 versus 0.61 h, P = 0.002). In contrast, the volumes of the central compartment (ca. 5.8 liters for both groups), the volumes of distribution at steady state (HV, 37.6 liters; patients, 55.9 liters), and the elimination half-lives (HV, 39.6 h; patients, 52.7 h) were not significantly different between HV and neutropenic patients. Interindividual variabilities of rates of clearance (coefficient of variation [CV], 43%) and elimination half-lives (CV, 56%) were mainly explained by the variabilities among rates of creatinine clearance. Interindividual variabilities of the volumes of the central compartment (CV, 33%) and the volumes of distribution at steady state (CV = 51%) were correlated to interindividual variabilities among numbers of leukocytes and the ages of patients, respectively. On the basis of the population PK model of teicoplanin, simulations were made to optimize the dosing schedule. A supplemental 6 mg/kg dose of teicoplanin at 36 h resulted in a trough concentration at 48 h of 16.0 +/- 4.5 mg/liter, with only 7% of patients having a trough concentration of less than 10 mg/liter, compared with 46% of patients on the usual schedule.

Adult↗
PubMed1995

Determination of piracetam in human plasma and urine by liquid chromatography.

A method for the determination of piracetam in human plasma and urine by liquid chromatography with absorbance detection at 206 nm and isocratic elution is proposed. The assay involved a liquid-liquid extraction into hexane-2-propanol at pH 9.2. The calibration graphs were linear in the range 3-40 mg/l in plasma and 100-2000 mg/l in urine. Bias was negligible and coefficients of variation were less than 10% throughout the working range except at 100 mg/l in urine. The limits of quantification were 3 mg/l in plasma and 100 mg/l in urine. The assay was reliably used for pharmacokinetic studies in humans after administration of 800 mg of piracetam per os.

Chromatography, High Pressure Liquid↗
PubMed1995

Pharmacokinetics of amoxicillin coadministered with a saline-polyethylene glycol solution in healthy volunteers.

The pharmacokinetics of orally administered amoxicillin were investigated in 12 healthy volunteers in a crossover design. They received either a placebo or a saline-polyethylene glycol solution (SPG) for 4 d, the last dose being given simultaneously with 1 g amoxicillin; blood samples were drawn for the next 12 h. Amoxicillin kinetics were similar in the two treatments but small differences in some pharmacokinetic parameters reached significance. The mean +/- SD area under the curve was lower with SPG (43.8 +/- 6.8 against 47.8 +/- 8.2 mg h L-1, p < 0.05) but the treatments were equivalent according to Westlake's test (95% confidence interval = 14.95%). Analysis of SPG against placebo amoxicillin absorption kinetics after fitting the data to a Weibull model revealed a longer duration of the absorption, a slower rate of absorption, and a different shape of the curve. No clinical consequences are expected from these minor variations but possible mechanisms could be relevant to other drugs.

Adult↗
PubMed1995

A population pharmacokinetic study of alminoprofen penetration into synovial fluid.

The pharmacokinetics of alminoprofen in plasma and synovial fluid (SF) at steady state (300 mg t.i.d.) was studied in 45 patients with knee effusion. Plasma and SF samples, one each per patient, were obtained. Six groups were made according to the time of sampling after ingestion of the 13th dose: 1 h (n = 7), 2 h (n = 7), 4 h (n = 7), 6 h (n = 10), 8 h (n = 6), 12 h (n = 8). A three-compartment model was used to describe alminoprofen kinetics in plasma and SF, with two parameterizations, a 'classical' and a 'physiological' one. The non-linear mixed effect model approach was used to estimate the mean and variance of the pharmacokinetic parameters. The mean +/- SE of the estimates (coefficient of variation of interindividual variability as a percentage) were volume of distribution, 11.0 +/- 1.711 (12%); elimination rate constant, 0.236 +/- 0.025 h-1 (18%); absorption rate constant 2.80 +/- 0.31 h-1 (464%), clearance of influx into SF, 0.29 +/- 0.14 mL min-1; clearance of efflux into plasma, 0.56 +/- 0.25 mL min-1. These two clearances were not significantly different, which indicates that passive diffusion occurs in both directions. The mean +/- SD alminoprofen concentration versus time curve in plasma and SF at steady state was simulated and showed that the mean +/- SD maximal concentration in SF was 8.1 +/- 6.3 mg L-1 and was obtained 4 h after dose administration.

Absorption↗